In 1999, the New York State Department of Health asked me to test brain samples from people in Queens experiencing encephalitis, or brain inflammation. Surprisingly, we found they were infected with West Nile virus, a mosquito-borne virus that had never been reported before in North America. How did a virus endemic in Africa and the Middle East end up in Queens?
At the time, scientists posited that there were stowaway mosquitoes on a flight from Tel Aviv. It seemed plausible that these stowaways fed on infected geese in Israel before infecting birds in New York. Local mosquitoes that fed on the New York birds then fed on people, and now we had an outbreak.
Like today with the origins of Covid-19, there were other, often polarizing, theories. Back in 1999 there were claims that the virus had been bioengineered by Saddam Hussein.
Although the global community never officially pinned down the provenance of the West Nile virus, the outbreak was brought under control by reducing the mosquito population in Queens — West Nile nonetheless remains the leading cause of mosquito-borne disease in the continental United States. Since 1999 it has infected at least seven million people, resulting in more than 51,000 cases of encephalitis and more than 2,300 deaths.
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