So far this year, at least ten people, including four in Florida, one in Georgia and five in the New York City area have turned up positive.
Last month, a study published in The Lancet estimated on the basis of sample blood tests and interviews that 8,200 people in the New York City area in 1999 came down with asymptomatic West Nile infections and about 1,700 experienced some flu-like symptoms.
Ozone and the Immune System
Valuable clues have not been investigated about the possible role of air quality in the outbreaks that began in the New York area in 1999. Outbreaks have since occurred in other regions of the country.
The summer of 1999 in New York City was extremely hot and, according to the New York State Department of Environmental Conservation (DEC), the smog was the worst in more than a decade. Smog includes ozone, which forms in the air from other toxic substances, including nitrogen oxides and volatile organic compounds.
It is scientifically established that ozone can affect the body's immune system so that the ability to fight infection may be impaired. It also can cause damage to the brain and lungs.
Steady Flow of Dead Crows
As New Yorkers baked in the heat that summer and were exposed to high levels of ozone, veterinarians and pathologists began to receive calls about unusual numbers of bird deaths.
In Delmar, near Albany, a veteran wildlife expert at the DEC's wildlife pathology unit, Ward Stone, began to receive a steady flow of dead crows, the most he had seen in 30 years.
He figured the heat and the lack of rain had somehow exposed old pesticides in soil and vegetation. It seemed the birds were being poisoned.
Stone then requested the standard type of toxicology testing. In looking for pesticide residues, it is routine to check for low levels of the enzyme cholinesterase. It has become standard practice that even if there are very little or no pesticide residues found in the birds, if the cholinesterase levels are low, then it is deemed likely that the death was due to pesticide poisoning.
On the basis of the tests, he began to theorize that the epidemic of dead birds was likely due to pesticides.
Stone didn't request tests to determine if bad air quality was playing a role in the bird deaths even though high ozone levels can also affect cholinesterase levels.
"We don't order those tests because there are no funds to do that kind of work," he said.
In fact, Stone couldn't recall anyone in his line of work doing air toxicology tests on birds.
When Stone's conclusions about pesticides and dead birds were about ready to be released in a DEC report, a human mystery disease was given an identity.
New York Mayor Rudolph Giuliani held a press conference on Sept. 3, 1999, to announce that scientists at the Centers for Disease Control and Prevention in Atlanta had identified the St. Louis encephalitis (SLE) virus, which is transmitted by mosquitoes, as the culprit in the hospitalizations of several elderly patients. They initially had high fever, headaches and altered mental status and gradually showed signs of brain inflammation.
Soon helicopters and trucks began spraying areas of New York City with the highly toxic insecticide, malathion.
With several scientific groups conducting further genetic tests, it was soon agreed that the culprit was actually West Nile virus and not SLE, Kunjin virus, which was also a major suspect, is another member of this family.