Bird blood fills up with the virus rapidly over several days. During that time, insects can bite infected birds and then bite a human who can also become ill. Photograph of Culex pipiens female mosquito, courtesy Entomology Image Gallery. These mosquitoes aren't interested in biting humans. When the mosquito starts biting humans, the virus spills out of its natural cycle.
Birds bitten by infected mosquitoes are infectious from four to eight days.
The virus incubation period in humans is five to fifteen days. Most people fight off the West Nile Fever Virus without getting sick. For those who do get sick, the fatality rate is not very high, about ten to fifteen percent. But despite the low fatality rate and cumbersome transmission cycle, speculation emerged that the West Nile Fever virus might have been artificially engineered as a bioterrorism weapon by scientists working for Saddam Hussein or other U. S. enemies to deliberately hurt Americans. That question and others were the subject of a meeting last week in Ft.