| does cross-sex transmission increase the severity of polio infection? a study of multiple family cases. | previous studies have suggested that transmission of measles virus from the opposite sex increases the severity of infection; however, the role of gender in the transmission of other infections has not been examined. multiple polio cases within a family usually occur simultaneously, and are therefore likely to be secondary to a common subclinical index case. the few clinical polio cases that appear much later than any other clinical case are likely to be tertiary cases. if cross-sex transmission ... | 2002 | 12064690 |