Hot summer may be behind West Nile outbreak in US
Date: 09-Aug-02
Country: USA
Author: Paul Simao
The agency noted that the bulk of the cases occurred in the deep Southern states of Louisiana, Texas and Mississippi, though isolated infections have been reported as far away as Illinois and Washington, D.C.
Dr. Lyle Petersen, a West Nile expert with the CDC, said it was possible that high temperatures this summer had created an ideal incubator for mosquitoes. The insects contract the virus from infected birds and then spread it to humans.
"The kinds of mosquitoes that transmit West Nile virus like to breed in very small, murky pools of water, and during hot weather larger pools condense into smaller pools," said Petersen, who added that the CDC was working with local health officials to monitor and control mosquito populations.
Although previous outbreaks in Israel, Romania, Russia and New York City coincided with bouts of hot weather, Petersen cautioned that other environmental factors likely had also played a part in the current outbreak.
West Nile is common in Africa and Asia but was unknown in the Americas until 1999 when an outbreak killed seven people in the New York borough of Queens. It has since spread quickly.
At least 23 people have died after contracting the virus in the United States.
On Thursday, one day after confirming the first human case of the disease in Washington, D.C., officials in the nation's capital urged the public to be vigilant.
"We need to do this together," said Theodore Gordon, the district's senior deputy director for public health assurance, at a news conference. "People have to go in their backyards and look for those situations and conditions that may lend themselves to mosquito breeding."
WEST NILE RARELY SERIOUS
Most people who contract West Nile suffer nothing more than headaches and flu-like symptoms, but the elderly, chronically ill and those with weak immune systems can develop fatal encephalitis and meningitis when infected.
The average age of 98 people infected this year is 55, according to the CDC. About 60 percent were men.
At least 36 states, stretching from Massachusetts to Texas, and the District of Columbia have reported some West Nile activity in 2002. The virus, which is spread largely through bird migrations, has also been detected in parts of Canada.
Mosquitoes contract West Nile from infected birds and then pass it on to human hosts. The virus can not be spread from person to person or from birds to humans.
Incidence of the disease tends to drop off when temperatures fall below 55 degrees (13 Celsius) and mosquitoes become dormant. But West Nile can spread again when the insects become active in spring.
Although more common, the risk of contracting the virus is still extremely low and can be reduced further if people use mosquito repellent, wear long sleeves and pants at night, and eliminate pools of standing water where mosquitoes breed.
