SAN JOSE, CALIF. - Like any new immigrant, the deadly West Nile virus became American almost immediately after landing on our shores -- altering itself to fit in and then infecting a popular backyard bird to secure a firm foothold in its new home.
That is the conclusion of a decadelong analysis by University of California, Santa Cruz, biologist Marm Kilpatrick, who explored the ecology of an infectious disease that killed five Californians last summer and sickened another 197, up from 82 last year.
"Just like other invasive species, the virus starts adapting to its new environment," Kilpatrick said.
The West Nile virus has done so well because it took advantage of a species that thrives around people: the American robin. One of the most familiar birds, its numbers have surged along with the popularity of lawns at homes, parks and schoolyards. Kilpatrick dubs them "super-spreaders."
Origin in Africa
The West Nile virus was discovered in Uganda in 1937. In some parts of Africa, more than 80 percent of adults have been infected with the disease that can cause fever, diarrhea, body aches and vomiting. For reasons not well understood, many never become ill.
Shortly after arriving in New York in 1999, the virus started changing -- evolving to become a new and distinct strain, the research shows. It probably smuggled itself into America within an infected mosquito on a transatlantic airplane. The original New York strain seemed to match a strain found in Israel, suggesting Mideast origins. But now it's different.
This new strain is transmitted more efficiently by local mosquitoes than the original.
