Last month, Leis asked a Food and Drug Administration scientist who studies the genetics of the virus whether a new, more virulent strain was circulating. “You are absolutely right . . . that new genetic variants of WNV might have appeared this year,” the scientist replied in an Oct. 23 e-mail obtained by The Washington Post. The scientist continued that “it is not easy to correlate” the new mutations with any specific type of brain damage. Thirty minutes after Leis *received the message, another *e-mail from the same scientist arrived. It said the previous message had been “recalled.”
When contacted by phone, the FDA scientist, who works at the agency’s Center for Biologics Evaluation and Research, declined to discuss the messages, saying that his superiors had instructed him not to talk to reporters. In an e-mail, FDA spokeswoman Heidi Rebello said that the agency is studying the genetics of West Nile viruses collected from 270 blood donors this year but that “it is premature for us to draw any conclusions about new genetic variants . . . or of any possible association of new genetic variants with increased virulence.”
Centers for Disease Control and Prevention/Reuters - West Nile virus, spread by mosquitoes, can lead to inflammation of the brain, damaging its speech, language and thinking centers.
West Nile virus, made of error-prone RNA instead of the hardier DNA found in human cells, can evolve rapidly. In 2002, a new strain appeared that quickly churns out copies of itself inside mosquitoes. This fast-replicating version swiftly replaced the earlier dominant variety. In 2003, another genetic variant, now dubbed the Southwestern strain, appeared in New Mexico and Arizona. The West Nile virus, first described in Uganda in 1937, arrived in New York City in 1999, killing eight in the city. Infected birds transmit the virus to mosquitoes, which then infect people, who cannot infect one another. By 2003, the virus had crossed the country.
So far this year, health authorities have reported more than 5,000 cases of West Nile illness and 228 deaths in 48 states, with Texas, California, Illinois and Michigan having the most cases. The CDC has classified about half of the illnesses as “neuroinvasive” — meaning the virus has gotten into the spinal cord or brain, causing encephalitis or other brain ailments. That’s the most dangerous type of illness caused by West Nile virus. In the other cases, patients come down with fevers or other flulike symptoms.