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yellow fever vaccine. iv. reactogenicity and antibody response in volunteers inoculated with a vaccine free from contaminating avian leukosis viruses. 19724333781
observations on dengue fever, benign protector and killer: a dr. jekyll and mr. hyde. 19694388466
detection of arboviral rna directly from mosquito homogenates by reverse-transcription-polymerase chain reaction.many arthropod-borne viruses (arboviruses) are important human pathogens medically. the development of an effective technique to detect the viruses by using nucleic acid amplification, such as polymerase chain reaction (pcr), improves not only clinical diagnosis but also virologic surveillance of mosquito vectors in the field. in this study, the development of an improved and simplified assay is described for detection of mosquitoes infected with eastern equine encephalitis (eee) virus, cache va ...200111337046
vector competence of california mosquitoes for west nile virus.to identify the mosquito species competent for west nile virus (wnv) transmission, we evaluated 10 california species that are known vectors of other arboviruses or major pests: culex tarsalis, cx. pipiens pipiens, cx. p. quinquefasciatus, cx. stigmatosoma, cx. erythrothorax, ochlerotatus dorsalis, oc. melanimon, oc. sierrensis, aedes vexans, and culiseta inornata. all 10 became infected and were able to transmit wnv at some level. ochlerotatus, culiseta, and aedes were low to moderately efficie ...200212498652
us fails to quantify threat of west nile virus. 200312736641
vector competence of culex tarsalis from orange county, california, for west nile virus.to evaluate the vector competence of culex tarsalis coquillett for west nile virus (wn), females reared from larvae collected in huntington beach, orange county, ca, were fed on 2-3-day-old chickens previously inoculated with a new york strain (crow 397-99) of wn. the cx. tarsalis mosquitoes were efficient laboratory vectors of wn, with estimated transmission rates of 81% and 91% for mosquitoes that ingested 10(6.5) or 10(7.3) plaque-forming units of wn/ml of blood, respectively. based on effici ...200212737548
california state mosquito-borne virus surveillance and response plan: a retrospective evaluation using conditional simulations.the california mosquito-borne virus surveillance and response plan recently was developed to provide a semi-quantitative means for assessing risk for western equine encephalomyelitis (wee) or st. louis encephalitis (sle) viruses and to provide intervention guidelines for mosquito control and public health agencies during periods of heightened risk for human infection. west nile virus recently has arrived in california, and the response plan also will provide a baseline for assessing the risk for ...200312812335
surveillance for acute insecticide-related illness associated with mosquito-control efforts--nine states, 1999-2002.ground and aerial applications of insecticides are used to control populations of adult mosquitoes, which spread such diseases as west nile virus--related illness, eastern equine encephalitis, and dengue fever. this report summarizes investigations of illnesses associated with exposures to insecticides used during 1999-2002 to control mosquito populations in nine states (arizona, california, florida, louisiana, michigan, new york, oregon, texas, and washington) (estimated 2000 population: 118 mi ...200312855943
arbovirus surveillance in rhode island: assessing potential ecologic and climatic correlates.during 1995-2000, mosquitoes were collected from sites throughout rhode island and tested for the presence of arboviruses. mosquito trapping was done weekly from june to october with co2-baited light traps. in all, 186,537 mosquitoes belonging to 7 different genera were collected, of which coquillettidia perturbans was most abundant. a total of 6,434 pools were processed for arbovirus isolation, from which 193 arboviral isolations were made. these included 109 highlands j, 71 eastern equine ence ...200314524538
vertical transmission of west nile virus by three california culex (diptera: culicidae) species.three california culex species previously identified as efficient laboratory vectors of west nile (wn) virus were tested for their capability to vertically transmit wn virus. wild-caught culex pipiens pipiens l., culex pipiens quinquefasciatus say, and two populations of culex tarsalis coquillett females were inoculated intrathoracically with 10(2.7 +/- 0.1) plaque-forming units of wn virus. f1 progeny were reared at 18 degrees c and subsequently tested as adults for infectious virus on vero cel ...200314765647
west nile virus activity--united states, june 9-15, 2004.as of june 15, a total of 14 human cases of west nile virus (wnv) illness had been reported to cdc through arbonet from five states. ten cases were reported from arizona, and one case each from california, new mexico, south dakota, and wyoming (figure). ten (71%) of the cases occurred in males; the median age of patients was 53 years (range: 9-69 years), and dates of illness onset ranged from may 8 to june 1.200415201846
west nile virus activity--united states, june 16-22, 2004.as of june 22, 2004, seven states reported a total of 32 human cases of west nile virus (wnv) illness to cdc through arbonet. twenty cases were reported from arizona, six cases from california, two cases from florida, and one case each from nebraska, new mexico, south dakota, and wyoming. twenty-three (72%) of the cases occurred in males; the median age of patients was 52 years (range: 9-78 years), and dates of illness onset ranged from may 8 to june 7. sixteen (50%) of the patients had neuroinv ...200415215743
west nile virus activity--united states, june 23-29, 2004.as of june 29, eight states had reported a total of 57 human cases of west nile virus (wnv) illness to cdc through arbonet in 2004. a total of 38 cases had been reported from arizona, 10 from california, three from new mexico, two from florida, and one each from michigan, nebraska, south dakota, and wyoming. thirty-six (64%) of the cases occurred in males; the median age of patients was 53 years (range: 9-84 years), and dates of illness onset ranged from april 23 to june 15. of the 57 cases, one ...200415229416
west nile virus activity--united states, june 30-july 6, 2004.during june 30-july 6, a total of 21 human cases of west nile virus (wnv) illness were reported from two states (arizona and california). during 2004, eight states have reported a total of 78 human cases of wnv illness to cdc through arbonet. of these, 57 (73%) were reported from arizona. forty-seven (61%) of the 78 cases occurred in males; the median age of patients was 53 years (range: 1-84 years); the dates of illness onset ranged from april 23 to june 28; and one case was fatal.200415241302
west nile virus activity united states, july 7-13, 2004.during the week of july 7-13, a total of 30 human west nile virus illness cases were reported from four states (arizona, california, colorado, and iowa). during 2004, a total of 10 states have reported a total of 108 cases of human west nile virus (wnv) illness to cdc through arbonet. of these, 66 (61%) were reported from arizona. sixty-one (58%) of the 108 cases occurred in males; median age of patients was 52 years (range: 1-84 years); dates of illness onset ranged from april 23 to july 5; and ...200415254454
west nile virus activity--united states, july 14-20, 2004.during the week of july 14-20, a total of 74 cases of human west nile virus (wnv) illness were reported from seven states (arizona, california, florida, new mexico, new york, south dakota, and texas).200415269701
west nile virus activity--united states, july 21-27, 2004.during july 21-27, a total of 83 cases of human west nile virus (wnv) illness were reported from 13 states (alabama, arizona, arkansas, california, colorado, florida, illinois, iowa, missouri, new mexico, ohio, pennsylvania, and south dakota).200415282450
west nile virus activity--united states, july 28-august 3, 2004.during july 28-august 3, a total of 141 cases of human west nile virus (wnv) illness were reported from 11 states (alabama, arizona, california, colorado, florida, illinois, nevada, new york, north dakota, south dakota, and texas). during 2004, a total of 20 states have reported a total of 406 cases of human wnv illness to cdc through arbonet. of these, 247 (61%) were reported from arizona. a total of 226 (57%) of the 406 cases occurred in males; the median age of patients was 51 years (range: 1 ...200415295314
infectious disease surveillance update. 200415298027
west nile virus activity--united states, august 4-10, 2004.during august 4-10, a total of 89 cases of human west nile virus (wnv) illness were reported from 14 states (alabama, arizona, california, florida, illinois, kentucky, louisiana, minnesota, mississippi, missouri, new mexico, north dakota, south dakota, and wyoming).200415306758
west nile virus activity--united states, august 11-17, 2004.during august 11-17, a total of 194 cases of human west nile virus (wnv) illness were reported from 17 states (alabama, arizona, california, colorado, florida, illinois, louisiana, maryland, minnesota, mississippi, missouri, new mexico, ohio, south dakota, texas, utah, and virginia).200415318160
west nile virus activity--united states, august 18-24, 2004.during august 18-24, a total of 154 cases of human west nile virus (wnv) illness were reported from 18 states (alabama, arizona, california, colorado, connecticut, florida, georgia, illinois, kentucky, minnesota, mississippi, missouri, nevada, new mexico, north carolina, south dakota, tennessee, and wisconsin).200415329654
west nile virus activity--united states, august 25-31, 2004.during august 25-31, a total of 210 cases of human west nile virus (wnv) illness were reported from 14 states (arizona, california, florida, illinois, indiana, kansas, maryland, minnesota, montana, nevada, new mexico, north dakota, oklahoma, and pennsylvania).200415343148
west nile virus activity--united states, september 8-14, 2004.during september 8-14, a total of 195 cases of human west nile virus (wnv) illness were reported from 26 states (alabama, arizona, arkansas, california, colorado, florida, georgia, idaho, illinois, iowa, kansas, maryland, minnesota, missouri, nebraska, nevada, new mexico, new york, north dakota, oklahoma, oregon, pennsylvania, south dakota, tennessee, texas, and wisconsin).200415371969
west nile virus activity--united states, september 15-21, 2004.during september 15-21, a total of 218 cases of human west nile virus (wnv) illness were reported from 21 states (arizona, california, florida, illinois, indiana, kansas, maryland, michigan, minnesota, mississippi, missouri, nebraska, nevada, new mexico, north dakota, oklahoma, south dakota, texas, utah, wisconsin, and wyoming).200415385920
west nile virus activity--united states, september 22-28, 2004.during september 22-28, a total of 180 cases of human west nile virus (wnv) illness were reported in the district of columbia (dc) and 24 states (alabama, arizona, california, georgia, illinois, iowa, kansas, kentucky, louisiana, maryland, michigan, minnesota, mississippi, missouri, montana, nebraska, nevada, new mexico, ohio, pennsylvania, texas, utah, wisconsin, and wyoming).200415457147
west nile virus activity--united states, september 29-october 5, 2004.during september 29-october 5, a total of 81 cases of human west nile virus (wnv) illness were reported from 18 states (alabama, arizona, arkansas, california, florida, georgia, illinois, iowa, kansas, kentucky, minnesota, missouri, ohio, oklahoma, pennsylvania, south dakota, texas, and virginia).200415470326
west nile virus in california.west nile virus (wnv) was first isolated in california during july 2003 from a pool of culex tarsalis collected near el centro, imperial county. wnv transmission then increased and spread in imperial and coachella valleys, where it was tracked by isolation from pools of cx. tarsalis, seroconversions in sentinel chickens, and seroprevalence in free-ranging birds. wnv then dispersed to the city of riverside, riverside county, and to the whittier dam area of los angeles county, where it was detecte ...200415496236
west nile virus activity--united states, october 13-19, 2004.during october 13-19, a total of 200 cases of human west nile virus (wnv) illness were reported from 20 states (arizona, arkansas, california, colorado, illinois, indiana, iowa, kansas, maryland, michigan, mississippi, missouri, nevada, new mexico, north carolina, oklahoma, pennsylvania, south dakota, wisconsin, and wyoming).200415499683
west nile virus activity--united states, october 20-26, 2004.during october 20-26, a total of 80 cases of human west nile virus (wnv) illness were reported from 16 states (arizona, california, florida, iowa, kentucky, louisiana, michigan, mississippi, missouri, montana, nebraska, new york, ohio, south dakota, texas, and utah).200415514584
west nile virus activity--united states, november 3-8, 2004.during november 3-8, a total of 41 cases of human west nile virus (wnv) illness were reported from seven states (california, maryland, minnesota, new mexico, oregon, tennessee, and texas).200415538322
antibody response to culex tarsalis salivary gland antigens among sentinel chickens in california.the arboviral surveillance program in california depends in part on sentinel chickens to detect western equine encephalomyelitis virus, st. louis encephalitis virus, and west nile virus activity. from 2000 through 2002, 1,578 serum specimens from 34 sentinel flocks in northern and southern california were tested for antibodies to culex tarsalis salivary gland antigens. sentinel chickens that were seropositive for mosquito salivary gland antigens were more likely to seroconvert to st. louis encep ...200515827292
west nile virus among blood donors in the united states, 2003 and 2004.west nile virus first appeared in the united states in 1999 and has since spread throughout the contiguous states, resulting in thousands of cases of disease. by 2002, it was clear that the virus could be transmitted by blood transfusion, and by the middle of 2003, essentially all blood donations were being tested for west nile virus rna with the use of investigational nucleic acid amplification tests; testing was performed on individual samples or on "minipools" of up to 16 donations.200516079368
nesting ardeid colonies are not a focus of elevated west nile virus activity in southern california.a large nesting colony of ardeid birds at the finney-ramer wildlife refuge in imperial county, california, did not appear to be a focus of west nile virus (wnv) amplification during the summer of 2004. blood samples taken during june and july from 155 nestlings of four species of ardeid birds (cattle egrets, black-crowned night herons, great egrets, and snowy egrets) and five nestling double-crested cormorants yielded a single wnv isolation from a 3-week-old cattle egret. antibody was detected b ...200516187895
west nile virus infection in the pediatric population.in 2004, los angeles county confirmed 11 cases of symptomatic west nile virus (wnv) infections in children younger than 18 years of age. eight had wnv fever, 2 had meningitis and 1 had encephalitis. fever, rash, nausea and vomiting were the most prominent symptoms at presentation; median duration of illness was 7 days. clinicians should be aware of the risk of wnv illness, confirm this diagnosis and report suspected wnv cases to their local health department.200616395109
2004 california pediatric west nile virus case series.relatively few pediatric west nile virus cases have been recognized in the united states since the virus was first identified in 1999. we reviewed the clinical characteristics of 23 cases in pediatric patients that occurred in california in 2004 to better understand the infection in this population.200616395112
a dietary risk assessment of the pyrethroid insecticide resmethrin associated with its use for west nile virus mosquito vector control in california.an outbreak of human illnesses associated with west nile virus (wnv) occurred in new york city in 1999. since then, it has gradually spread westwards, reaching northern california for the first time in 2005. wnv is transmitted by several mosquito species and birds serve as the main reservoir. several control measures have been used, targeting both the aquatic larvae and the adult mosquitoes. in the latter case, roosting birds in trees are sprayed with pyrethroid insecticides because these are hi ...200616518516
effects of temperature on the transmission of west nile virus by culex tarsalis (diptera: culicidae).culex tarsalis coquillett females were infected with the ny99 strain of west nile virus (family flaviviridae, genus flavivirus, wnv) and then incubated under constant temperatures of 10-30 degrees c. at selected time intervals, transmission was attempted using an in vitro capillary tube assay. the median time from imbibing an infectious bloodmeal until infected females transmitted wnv (median extrinsic incubation period, eip50) was estimated by probit analysis. by regressing the eip rate (invers ...200616619616
overwintering of west nile virus in southern california.west nile virus (family flaviviridae, genus flavivirus, wnv) invaded southern california during 2003, successfully overwintered, amplified to epidemic levels, and then dispersed to every county in the state. although surveillance programs successfully tracked and measured these events, mechanisms that allowed the efficient overwintering and subsequent amplification of wnv have not been elucidated. our current research provided evidence for three mechanisms whereby wnv may have persisted in south ...200616619621
role of corvids in epidemiology of west nile virus in southern california.the invasion of different southern california landscapes by west nile virus (wnv) and its subsequent amplification to epidemic levels during 2004 enabled us to study the impact of differing corvid populations in three biomes: the hot colorado desert with few corvids (coachella valley), the southern san joaquin valley (kern county) with large western scrub-jay but small american crow populations, and the cool maritime coast (los angeles) with a large clustered american crow population. similar su ...200616619622
west nile virus activity--united states, january 1-august 15, 2006.this report summarizes west nile virus (wnv) surveillance data reported to cdc through arbonet as of 3 a.m. mountain daylight time, august 15, 2006. a total of 26 states had reported 388 cases of human wnv illness to cdc. a total of 214 (56%) cases for which such data were available occurred in males; median age of patients was 49 years (range: 2-91 years). dates of illness onset ranged from january 6 to august 10; a total of 13 cases were fatal. a total of 68 presumptive west nile viremic blood ...200616915222
role of california (callipepla californica) and gambel's (callipepla gambelii) quail in the ecology of mosquito-borne encephalitis viruses in california, usa.gambel's and california quail were infected repeatedly whenever western equine encephalomyelitis virus (weev), st. louis encephalitis virus (slev), and (wnv) west nile virus were active during summer in california. the timing of virus appearance and quail infection coincided well with the appearance of chicks in nature, leading us to hypothesize that large coveys containing these non-immune birds could be important in focal virus amplification in rural settings. however, experimental infection s ...200616989564
developing global climate anomalies suggest potential disease risks for 2006-2007.el niño/southern oscillation (enso) related climate anomalies have been shown to have an impact on infectious disease outbreaks. the climate prediction center of the national oceanic and atmospheric administration (noaa/cpc) has recently issued an unscheduled el niño advisory, indicating that warmer than normal sea surface temperatures across the equatorial eastern pacific may have pronounced impacts on global tropical precipitation patterns extending into the northern hemisphere particularly ov ...200617194307
seasonal variation in susceptibility to west nile virus infection in culex pipiens pipiens (l.) (diptera: culicidae) from san joaquin county, california. 200617249364
serologic evidence of west nile virus exposure in north american mesopredators.sera from 936 mammalian mesopredators (virginia opossums, gray foxes, striped skunks, hooded skunks, raccoons, a bobcat, and a red fox) were collected during 2003 and 2004 in california, arizona, texas, louisiana, ohio, and wyoming and screened for flavivirus-specific antibodies by an epitope-blocking enzyme-linked immunosorbent assay (blocking elisa). serum samples positive for antibodies against flaviviruses were screened for west nile virus (wnv)-specific antibodies by blocking elisa and sele ...200717255248
incidence and effects of west nile virus infection in vaccinated and unvaccinated horses in california.a prospective cohort study was used to estimate the incidence of west nile virus (wnv) infection in a group of unvaccinated horses (n = 37) in california and compare the effects of natural wnv infection in these unvaccinated horses to a group of co-mingled vaccinated horses (n = 155). horses initially were vaccinated with either inactivated whole virus (n = 87) or canarypox recombinant (n = 68) wnv vaccines during 2003 or 2004, prior to emergence of wnv in the region. unvaccinated horses were se ...200717274156
vector competence of culiseta incidens and culex thriambus for west nile virus.the vector competence of culiseta incidens (thomson) and culex thriambus dyar for west nile virus (wnv) were compared to cx. quinquefasciatus say or cx. tarsalis coquillett and cx. stigmatasoma dyar collected concurrently in california. culiseta incidens were less susceptible to oral infection than cx. quinquefasciatus, but transmitted virus at a significantly higher rate, thereby yielding comparable population transmission rates. culex thriambus was equally susceptible to oral infection and tra ...200617304934
evidence for a population expansion in the west nile virus vector culex tarsalis.population genetic structure of the west nile virus vector culex tarsalis was investigated in 5 states in the western united states using 5 microsatellite loci and a fragment of the mitochondrial reduced form of nicotinamide adenine dinucleotide dehydrogenase 4 (nd4) gene. nd4 sequence analysis revealed a lack of isolation by distance, panmixia across all populations, an excess of rare haplotypes, and a star-like phylogeny. microsatellites revealed moderate genetic differentiation and isolation ...200717339636
does feeding on infected mosquitoes (diptera: culicidae) enhance the role of song sparrows in the transmission of arboviruses in california?song sparrows, melopiza melodia, inoculated subcutaneously with either western equine encephalomyelitis virus (family togaviridae, genus alphavirus, weev) or west nile virus (family flaviviridae, genus flavivirus, wnv) developed elevated viremias, and they were considered to be competent experimental hosts for both viruses. however, birds that ingested from three to 20 mosquitoes containing comparable amounts of either weev or wnv failed to become infected, indicating limited oral susceptibility ...200717427703
west nile virus infection in tree squirrels (rodentia: sciuridae) in california, 2004-2005.west nile virus (wnv) transmission generally involves a mosquito vector and an avian reservoir host, with mammals as incidental hosts. although most mammalian wnv infections cause low or no morbidity or mortality, tree squirrels are susceptible to wnv-associated neurologic disease with infection prevalence comparable to that in dead birds. positive species included fox squirrel (sciurus niger), western gray squirrel (s. griseus), and eastern gray squirrel (s. carolinensis). kidney tissue (dissec ...200717488896
geographic variation in vector competence for west nile virus in the culex pipiens (diptera: culicidae) complex in california.we evaluated the susceptibility to infection and transmission of west nile virus (wnv) in seven populations of culex pipiens pipiens (l.), cx. p. quinquefasciatus say, and from populations containing cx. pipiens/quinquefasciatus hybrids in a north-south transect of california. samples were identified to species or as hybrid forms based on morphology of male terminalia. after 7 and 14 days of extrinsic incubation, few females were infected and none transmitted wnv from samples of cx. p. pipiens f ...200717627438
endemic human mosquito-borne disease in wisconsin residents, 2002-2006.west nile virus (wnv) and la crosse virus (lac) are the primary mosquito-borne arboviruses associated with human disease in wisconsin. we examined wnv and lac human illness surveillance data collected during 2002 through 2006.200717844707
nontarget effects of the mosquito adulticide pyrethrin applied aerially during a west nile virus outbreak in an urban california environment.in august 2006, a pyrethrin insecticide synergized with piperonyl butoxide (evergreen crop protection ec 60-6, mclaughlin gormley king company, golden valley, mn) was sprayed in ultralow volumes over the city of davis, ca, by the sacramento-yolo mosquito and vector control district to control mosquitoes transmitting west nile virus. concurrently, we evaluated the impact of the insecticide on nontarget arthropods by 1) comparing mortality of treatment and control groups of sentinel arthropods, an ...200717939516
enterovirus detection as a result of west nile virus surveillance.in this 2005 study from the los angeles county public health department laboratory, los angeles, ca, cerebrospinal fluid specimens submitted for west nile virus (wnv) serologic testing were also tested for enterovirus by real time reverse transcription-polymerase chain reaction and culture. approximately 10% of the wnv- specimens were positive for enterovirus. altered consciousness and muscle weakness were more common with wnv infection. results provide compelling evidence that laboratory testin ...200718024318
genetic deficiency of chemokine receptor ccr5 is a strong risk factor for symptomatic west nile virus infection: a meta-analysis of 4 cohorts in the us epidemic.west nile virus (wnv) causes disease in approximately 20% of infected humans. we previously reported that homozygosity for ccr5delta32, a nonfunctional variant of chemokine receptor ccr5, is markedly increased among symptomatic wnv-seropositive patients from arizona and colorado. to confirm this, we analyzed cohorts from california and illinois. an increase in ccr5-deficient subjects was found in both (for california, odds ratio [or], 4.2 [95% confidence interval {ci}, 1.5-11.9] [p= .004]; for i ...200818179388
high subclinical west nile virus incidence among nonvaccinated horses in northern california associated with low vector abundance and infection.although horse cases frequently are reported during west nile virus (wnv) outbreaks, few investigations have focused on the epidemiology of this transmission. from april to october 2003 to 2005, mosquito abundance and infection were monitored 3 days per week at an equine research facility at the university of california, davis. thirty-two nonvaccinated horses enrolled as controls in a vaccine study were bled monthly, and their serum was tested for evidence of wnv infection by plaque reduction ne ...200818187784
risk factors associated with human infection during the 2006 west nile virus outbreak in davis, a residential community in northern california.we collected a total of 15,329 mosquitoes during weekly sampling in davis, ca, from april through mid-october 2006 at 21 trap sites uniformly spaced 1.5 km apart over an area of approximately 26 km(2). of these mosquitoes, 1,355 pools of culex spp. were tested by multiplex reverse transcriptase-polymerase chain reaction, of which 16 pools (1.2%) were positive for west nile virus (wnv). a degree-day model with a developmental threshold of 14.3 degrees c accurately predicted episodic wnv transmiss ...200818187785
identification of culex pipiens complex mosquitoes in a hybrid zone of west nile virus transmission in fresno county, california.culex pipiens sensu lato mosquitoes were collected from 24 gravid traps (mid-june to mid-october, 2005) in fresno county, ca. captured gravid females were allowed to oviposit before sibling species identification by ace.2 pcr and detection of west nile virus (wnv) rna by rt-pcr were performed on the mother and her offspring. of the 442 cx. pipiens s.l. female mosquitoes collected, 88 were positive for wnv viral rna (peaked in august) with no significant differences among complex members or habit ...200818256434
risk factors for west nile virus neuroinvasive disease, california, 2005.in 2005, 880 west nile virus cases were reported in california; 305 case-patients exhibited neuroinvasive disease, including meningitis, encephalitis, or acute flaccid paralysis. risk factors independently associated with developing neuroinvasive disease rather than west nile fever included older age, male sex, hypertension, and diabetes mellitus.200718258047
hematophagous diptera collected from a horse and paired carbon dioxide-baited suction trap in southern california: relevance to west nile virus epizootiology.hematophagous diptera landing on a horse were removed by vacuum, and their numbers were related to a paired carbon dioxide-baited suction trap at three locations in southern california where west nile virus activity was high during the preceding year. insects collected from the horse included mosquitoes (nine species), biting midges (culicoides sonorensis wirth & jones), and black flies (simulium bivittatum malloch). mosquitoes were predominantly collected from the head, crest, withers, neck, ch ...200818283951
limited interdecadal variation in mosquito (diptera: culicidae) and avian host competence for western equine encephalomyelitis virus (togaviridae: alphavirus).historically, western equine encephalomyelitis virus (weev) caused large equine and human epidemics in the americas from canada into argentina. despite recent enhanced surveillance for west nile virus, there have been few reports of equine or human cases and little documented enzootic activity of weev. during the past three years, weev has been active again in california, but without human or equine cases. in the current study, we compared host and vector competence of representative weev isolat ...200818385369
efficacy of aerial spraying of mosquito adulticide in reducing incidence of west nile virus, california, 2005.epidemic transmission of west nile virus (wnv) in sacramento county, california, in 2005 prompted aerial application of pyrethrin, a mosquito adulticide, over a large urban area. statistical analyses of geographic information system datasets indicated that adulticiding reduced the number of human wnv cases within 2 treated areas compared with the untreated area of the county. when we adjusted for maximum incubation period of the virus from infection to onset of symptoms, no new cases were report ...200818439356
feasibility of routine individual donation testing for west nile virus rna during epidemic season using the investigational roche cobas taqscreen west nile virus test and cobas s 201 system prototype.minipool (mp) screening for west nile virus (wnv) rna may fail to detect presumptive viremic donations (pvds) detectable by individual donation screening (ids). most blood centers switch collection regions to ids when pvd detection by mp screening reaches a certain frequency. use of ids for all donations during wnv season was assessed during a clinical trial of the roche cobas taqscreen wnv test. also evaluated was whether pvd detection reliably identifies regions that should be targeted for ids ...200818466179
intensive early season adulticide applications decrease arbovirus transmission throughout the coachella valley, riverside county, california.in the coachella valley of california the seasonal onset of st. louis encephalitis virus (slev), western equine encephalomyelitis virus (weev), and west nile virus (wnv) has been detected consistently at the shoreline of the salton sea near the community of north shore. the timing and intensity of initial amplification in the culex tarsalis coquillett/wild bird cycle at this focus seemed closely linked to the subsequent dispersal of virus to the rest of the coachella valley and perhaps southern ...200818494603
persistent west nile virus transmission and the apparent displacement st. louis encephalitis virus in southeastern california, 2003-2006.west nile virus (family flaviviridae, genus flavivirus, wnv) invaded the colorado desert biome of southern california during summer 2003 and seemed to displace previously endemic st. louis encephalitis virus (family flaviviridae, genus flavivirus, slev, an antigenically similar flavivirus in the japanese encephalitis virus serocomplex). western equine encephalomyelitis virus (family togaviridae, genus alphavirus, weev), an antigenically distinct alphavirus, was detected during 2005 and 2006, ind ...200818533445
impact of aerial spraying of pyrethrin insecticide on culex pipiens and culex tarsalis (diptera: culicidae) abundance and west nile virus infection rates in an urban/suburban area of sacramento county, california.in response to an epidemic amplification of west nile virus (family flaviviridae, genus flavivirus, wnv), the sacramento and yolo mosquito and vector control district (symvcd) sprayed ultralow-volume (ulv) formulations of pyrethrin insecticide (evergreen ec 60-6: 6% pyrethrin insecticide, 60% piperonylbutoxide; mgk, minneapolis, mn, applied as 0.003 kg/ha [0.0025 lb/acre] ) over 218 km2 in north sacramento and 243.5 km2 in south sacramento on three consecutive evenings in august 2005. we evaluat ...200818714879
potential for the emergence of japanese encephalitis virus in california.the potential risk for the introduction and establishment of japanese encephalitis virus (jev) within california is described based on the literature. jev is a mosquito-borne arbovirus endemic to asia that when transmitted to humans can lead to japanese encephalitis (je), a disease affecting mostly children with a fatality rate up to 30%. the geographical expansion of jev in asia along with the recent introduction and rapid spread of west nile virus (wnv) across the united states, demonstrates t ...200918973447
delinquent mortgages, neglected swimming pools, and west nile virus, california.adjustable rate mortgages and the downturn in the california housing market caused a 300% increase in notices of delinquency in bakersfield, kern county. this led to large numbers of neglected swimming pools, which were associated with a 276% increase in the number of human west nile virus cases during the summer of 2007.200818976560
epidemiology of neuroinvasive arboviral disease in the united states, 1999-2007.from 1999-2007, the most common causes of neuroinvasive arboviral disease in the united states, after west nile virus (wnv), were california (cal) serogroup viruses, st. louis encephalitis virus (slev), and eastern equine encephalitis virus (eeev). the cal serogroup virus disease was primarily reported from appalachia and the upper midwest, slev disease from southern states, and eeev disease from areas along the atlantic and gulf coasts. children accounted for 88% of cal serogroup virus disease, ...200819052314
does variation in culex (diptera: culicidae) vector competence enable outbreaks of west nile virus in california?since the invasion of california by west nile virus (family flaviviridae, genus flavivirus, wnv) in 2003, we have annually monitored vector competence for the ny99 strain in culex tarsalis coquillett, culex pipiens quinquefasciatus say, culex p. pipiens l., and culex stigmatosoma dyar populations from four areas: deserts of coachella valley, densely urbanized maritime los angeles, southern san joaquin valley in kern county, and southern sacramento valley near davis in sacramento county. overall, ...200819058638
role of communally nesting ardeid birds in the epidemiology of west nile virus revisited.although herons and egrets in the family ardeidae frequently have been associated with viruses in the japanese encephalitis virus serocomplex, communal nesting colonies do not appear to be a focus of early season and rapid amplification of west nile virus (wnv) in california. evidence for repeated wnv infection was found by testing living and dead nestlings collected under trees with mixed species ardeid colonies nesting above in an oak grove near the university of california arboretum in davis ...200919125659
spatial spreading of west nile virus described by traveling waves.in this work, we propose a spatial model to analyze the west nile virus propagation across the usa, from east to west. west nile virus is an arthropod-borne flavivirus that appeared for the first time in new york city in the summer of 1999 and then spread prolifically among birds. mammals, such as humans and horses, do not develop sufficiently high bloodstream titers to play a significant role in the transmission, which is the reason to consider the mosquito-bird cycle. the model aims to study t ...200919167405
repeated west nile virus epidemic transmission in kern county, california, 2004-2007.west nile virus (wnv) has remained epidemic in kern county, ca, since its introduction in 2004 through 2007 when the human case annual incidence increased from 6-8 to 17 per 100,000, respectively. the 2007 increase in human infection was associated with contradicting surveillance indicators, including severe drought, warm spring but cool summer temperature anomalies, decreased rural and urban mosquito abundance but increased early season infection in urban culex quinquefasciatus say, moderate av ...200919198528
delinquent mortgages, neglected swimming pools, and west nile virus, california. 200919239785
spatially explicit west nile virus risk modeling in santa clara county, california.a geographic information system model designed to identify regions at risk for west nile virus (wnv) transmission was calibrated and tested with data collected in santa clara county, california. american crows that died from wnv infection in 2005 provided spatial and temporal ground truth. when the model was run with parameters based on culex tarsalis infected with the ny99 genotype of the virus, it underestimated wnv occurrence in santa clara co. the parameters were calibrated to fit the field ...200919514810
west nile virus detection in nonvascular feathers from avian carcasses.west nile virus (wnv) is a public health threat and has caused the death of thousands of north american birds. as such, surveillance for wnv has been ongoing, utilizing numerous biological specimens and testing methods. nonvascular (i.e., fully grown) feathers would provide a simple method of collection from either dead or live birds of all ages and molt cycles, with presumably less biosafety risk compared with other specimen types, including feather pulp. the current study evaluates wnv detecti ...200919737756
economic cost analysis of west nile virus outbreak, sacramento county, california, usa, 2005.in 2005, an outbreak of west nile virus (wnv) disease occurred in sacramento county, california; 163 human cases were reported. in response to wnv surveillance indicating increased wnv activity, the sacramento-yolo mosquito and vector control district conducted an emergency aerial spray. we determined the economic impact of the outbreak, including the vector control event and the medical cost to treat wnv disease. wnv disease in sacramento county cost approximately $2.28 million for medical trea ...201020202424
evaluation of efficacy and human health risk of aerial ultra-low volume applications of pyrethrins and piperonyl butoxide for adult mosquito management in response to west nile virus activity in sacramento county, california.the sacramento and yolo mosquito and vector control district (symvcd, also referred to as "the district") conducts surveillance and management of mosquitoes in sacramento and yolo counties in california. following an increase in numbers and west nile virus (wnv) infection rates of culex tarsalis and culex pipiens, the district decided on july 26, 2007, to conduct aerial applications of evergreen ec 60-6 (60% pyrethrins: 6% piperonyl butoxide) over approximately 215 km2 in the north area of sacra ...201020402352
west nile virus knowledge among hispanics, san diego county, california, usa, 2006. 201020678340
west nile virus emergence and persistence in los angeles, california, 2003-2008.west nile virus (wnv) invaded los angeles in september 2003, and during the subsequent five-year period followed a pattern of amplification, subsidence, and resurgence. enzootic transmission was tracked by abundance and infection incidence in culex pipiens quinquefasciatus and cx. tarsalis and by seroprevalence in peridomestic passerine birds, infection in dead birds, and seroconversions in sentinel chickens. culex p. quinquefasciatus served as the primary vector of wnv, with gravid traps servin ...201020682890
modeled response of the west nile virus vector culex quinquefasciatus to changing climate using the dynamic mosquito simulation model.climate can strongly influence the population dynamics of disease vectors and is consequently a key component of disease ecology. future climate change and variability may alter the location and seasonality of many disease vectors, possibly increasing the risk of disease transmission to humans. the mosquito species culex quinquefasciatus is a concern across the southern united states because of its role as a west nile virus vector and its affinity for urban environments. using established relati ...201020683620
pathology associated with west nile virus infections in the yellow-billed magpie (pica nuttalli): a california endemic bird.yellow-billed magpies (pica nuttalli, corvidae) are found exclusively in central california and have experienced alarming west nile virus (wnv)-associated mortality since 2004. the first reported case of wnv in the species was reported in july 2004. subsequently, 81% (304/374) of dead magpies submitted that year to the california department of health services dead bird surveillance program were wnv positive by polymerase chain reaction (pcr) test. we studied 43 magpie carcasses collected in 2004 ...201020688633
occurrence of west nile virus infection in raptors at the salton sea, california.we investigated the prevalence of west nile virus (wnv)-neutralizing antibodies and infectious virus, and the occurrence of overwinter transmission in two raptor species during january and march 2006 at the salton sea, imperial county, california. we captured 208 american kestrels (falco sparverius) (january, n=100; march, n=108) and 116 burrowing owls (athene cunicularia) (january, n=52; march, n=64). laboratory analysis revealed that 83% of american kestrels and 31% of burrowing owls were posi ...201020688694
migratory birds and the dispersal of arboviruses in california.each spring large numbers of neotropical migrants traversing the pacific flyway pass through the coachella valley enroute to northern destinations, providing an opportunity to test the hypothesis that mosquito-borne encephalitis viruses are introduced annually into california by migratory birds. a total of 5,632 sera were collected from 43 species of migrants during spring (april-june), of which 34 (0.61%) comprised of 14 species tested positive by enzyme immunoassay; only 10 were confirmed by p ...201020889869
public health pesticide use in california: a comparative summary.california pesticide use summary data and use reports from local vector control agencies were reviewed to document public health pesticide use patterns. during the 15-year period 1993-2007, public health pesticide use averaged 1.75 million lb (0.79 million kg) (ai), accounted for < 1% of reportable pesticide use statewide, and ranked below major crop uses and many nonagricultural uses. a review of reports from local vector control agencies (2004-07) indicated that their applications were princip ...201021033068
sentinel chicken seroconversions track tangential transmission of west nile virus to humans in the greater los angeles area of california.in los angeles, california, west nile virus (wnv) has followed a pattern of emergence, amplification, subsidence, and resurgence. a time series cross-correlation analysis of human case counts and sentinel chicken seroconversions revealed temporal concordance indicating that chicken seroconversions tracked tangential transmission of wnv from the basic passeriform-culex amplification cycle to humans rather than antecedent enzootic amplification. sentinel seroconversions provided the location and t ...201021036853
comparison of immunohistochemistry and polymerase chain reaction for detection of west nile virus in naturally infected dead birds.credible vector-borne disease surveillance programs, especially in developing countries with limited resources, must include diagnostic tests that are efficient, inexpensive and simple and safe to administer while maintaining high levels of sensitivity and specificity. since immunohistochemistry (ihc) includes most of these features, its sensitivity, specificity, predictive positive value (ppv) and predictive negative value (pnv) for west nile virus (wnv) screening were compared to those of the ...201021045374
economic conditions predict prevalence of west nile virus.understanding the conditions underlying the proliferation of infectious diseases is crucial for mitigating future outbreaks. since its arrival in north america in 1999, west nile virus (wnv) has led to population-wide declines of bird species, morbidity and mortality of humans, and expenditures of millions of dollars on treatment and control. to understand the environmental conditions that best explain and predict wnv prevalence, we employed recently developed spatial modeling techniques in a re ...201021103053
vector-host interactions governing epidemiology of west nile virus in southern california.southern california remains an important focus of west nile virus (wnv) activity, with persistently elevated incidence after invasion by the virus in 2003 and subsequent amplification to epidemic levels in 2004. eco-epidemiological studies of vectors-hosts-pathogen interactions are of paramount importance for better understanding of the transmission dynamics of wnv and other emerging mosquito-borne arboviruses. we investigated vector-host interactions and host-feeding patterns of 531 blood-engor ...201021118934
temporal and spatial alterations in mutant swarm size of st. louis encephalitis virus in mosquito hosts.st. louis encephalitis virus (slev; flaviviridae; flavivirus) is a member of the japanese encephalitis serocomplex and a close relative of west nile virus (wnv). although slev remains endemic to the us, both levels of activity and geographical dispersal are relatively constrained when compared to the widespread distribution of wnv. in recent years, wnv appears to have displaced slev in california, yet both viruses currently coexist in texas and several other states. it has become clear that vira ...201121215334
efficacy of three vaccines in protecting western scrub-jays (aphelocoma californica) from experimental infection with west nile virus: implications for vaccination of island scrub-jays (aphelocoma insularis).abstract the devastating effect of west nile virus (wnv) on the avifauna of north america has led zoo managers and conservationists to attempt to protect vulnerable species through vaccination. the island scrub-jay (aphelocoma insularis) is one such species, being a corvid with a highly restricted insular range. herein, we used congeneric western scrub-jays (aphelocoma californica) to test the efficacy of three wnv vaccines in protecting jays from an experimental challenge with wnv: (1) the fort ...201121438693
surveillance for west nile virus and vaccination of free-ranging island scrub-jays (aphelocoma insularis) on santa cruz island, california.abstract transmission of west nile virus (wnv) on mainland california poses an ongoing threat to the island scrub-jay (issj, aphelocoma insularis), a species that occurs only on santa cruz island, california, and whose total population numbers <5000. our report describes the surveillance and management efforts conducted since 2006 that are designed to understand and mitigate for the consequences of wnv introduction into the issj population. we suspect that wnv would most likely be introduced to ...201121438695
blood-feeding patterns of the culex pipiens complex in sacramento and yolo counties, california.mosquitoes in the culex pipiens complex are competent vectors of west nile virus (wnv; family flaviviridae, genus flavivirus) in the laboratory, and field-collected mosquitoes have tested positive for the virus in california and elsewhere. a better understanding of cx. pipiens complex blood-feeding patterns will help define the threat that these mosquitoes pose to human health and their role in wnv amplification in northern california. we collected blood-engorged cx. pipiens complex mosquitoes f ...201121485380
human jamestown canyon virus infection --- montana, 2009.jamestown canyon virus (jcv) is a mosquito-borne zoonotic pathogen belonging to the california serogroup of bunyaviruses. although jcv is widely distributed throughout temperate north america, reports of human jcv infection in the united states are rare. this is the first report of human jcv infection detected in montana, one of only 15 cases reported in the united states since 2004, when jcv became reportable. on may 26, 2009, a man aged 51 years with no travel history outside of montana went t ...201121617630
bloodmeal host congregation and landscape structure impact the estimation of female mosquito (diptera: culicidae) abundance using dry ice-baited traps.vegetation patterns and the presence of large numbers of nesting herons and egrets significantly altered the number of host-seeking culex tarsalis coquillett (diptera: culicidae) collected at dry ice-baited traps. the numbers of females collected per trap night at traps along the ecotone of eucalyptus stands with and without a heron colony were always greater or equal to numbers collected at traps within or under canopy. no cx. tarsalis were collected within or under eucaplytus canopy during the ...201121661310
west nile virus disease and other arboviral diseases --- united states, 2010.arthropod-borne viruses (arboviruses) are transmitted to humans primarily through the bites of infected mosquitoes and ticks. since west nile virus (wnv) was first detected in the western hemisphere in 1999, it has become the leading cause of neuroinvasive arboviral disease in the united states. however, several other arboviruses continue to cause sporadic cases and seasonal outbreaks of neuroinvasive disease (i.e., meningitis, encephalitis, or acute flaccid paralysis). this report summarizes su ...201121814163
early warning system for west nile virus risk areas, california, usa.the dynamic continuous-area space-time (dycast) system is a biologically based spatiotemporal model that uses public reports of dead birds to identify areas at high risk for west nile virus (wnv) transmission to humans. in 2005, during a statewide epidemic of wnv (880 cases), the california department of public health prospectively implemented dycast over 32,517 km2 in california. daily risk maps were made available online and used by local agencies to target public education campaigns, surveill ...201121801622
insect-specific flaviviruses from culex mosquitoes in colorado, with evidence of vertical transmission.mosquitoes were collected in colorado during 2006 and 2007 to examine spatial and seasonal patterns of risk for exposure to culex vectors and west nile virus. we used universal flavivirus primers to test pools of culex mosquitoes for viral rna. this led to the detection and subsequent isolation of two insect-specific flaviviruses: culex flavivirus (cxfv), which was first described from japan, and a novel insect flavivirus, designated calbertado virus (clbov), which has also been detected in cali ...201121734144
Mosquito host selection varies seasonally with host availability and mosquito density.Host selection by vector mosquitoes is a critical component of virus proliferation, particularly for viruses such as West Nile (WNV) that are transmitted enzootically to a variety of avian hosts, and tangentially to dead-end hosts such as humans. Culex tarsalis is a principal vector of WNV in rural areas of western North America. Based on previous work, Cx. tarsalis utilizes a variety of avian and mammalian hosts and tends to feed more frequently on mammals in the late summer than during the res ...201122206038
culex pipiens sensu lato in california: a complex within a complex?culex pipiens sensu lato populations represent significant nuisance pests and vectors of west nile virus in california. despite multiple years of investigation, identifying, controlling and understanding the behaviors and associated "biologies" of the complex members still remain a challenge. population structure cluster analysis using microsatellite markers revealed extensive population structuring, particularly in the central parts of the state, over and above what can be explained by the pres ...201223401951
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