The Heat Is Online

CDC Foresees Increase in WNV

CDC: Deadly West Nile virus spreading in US

Reuters News Service, July 27, 2001

ATLANTA - West Nile virus, the mosquito-borne illness that has killed at least eight people since surfacing in the northeastern United States two years ago, is spreading and could soon jump to other parts of the country, federal health experts said yesterday.

A report by the Centers for Disease Control and Prevention said the virus, which can cause deadly encephalitis or meningitis in birds, humans and other mammals, was turning up at levels double those found in bird populations last year.

CDC officials said they were not surprised the virus, which has largely been confined to northeastern states, had been detected in Florida and Georgia, and suggested it was only a matter of time before other regions were affected.

Earlier this month, a 73-year-old man from northern Florida became the first person in the state to acquire the virus. He is being treated in a hospital for encephalitis, a severe form of brain inflammation.

Infected birds have recently been found in Georgia.

"We had anticipated that we would see the virus move into different areas particularly as birds migrated to different parts of the United States," Dr. Stephen Ostroff, a CDC epidemiologist, told reporters in a teleconference.

"There is nothing to prohibit the virus from spreading into the Midwest either in birds or mosquitoes," said Ostroff, who added that the spread of the virus could depend on factors such as weather and bird migration patterns.

Most states along the Atlantic Coast as well as the District of Columbia have reported some exposure to the virus since it struck the New York City area in 1999, killing seven people and infecting dozens of others.


A New Jersey man died last year after contracting West Nile. New Jersey and Maryland were the two states with the highest numbers of infected birds in the first half of 2001, according to the CDC.

Separately, researchers were quoted in The Lancet medical journal on Friday as saying the outbreak of West Nile in New York City two years ago was worse than health officials had realised and may have affected several thousand people.

For every reported case of the virus that caused encephalitis there were probably 140 other infections with milder symptoms that were not correctly diagnosed.

"During the 1999 West Nile virus outbreak, thousands of symptomless and symptomatic West Nile viral infections probably occurred," said Dr Farzad Mostashari, a medical epidemiologist with the New York City Department of Health and the CDC.

Mostashari and his team estimated the extent of the outbreak by extrapolating the results of a blood sample study done on 677 people six weeks after the peak of the 1999 outbreak. It showed 2.6 percent were infected with the virus.

West Nile, which was common in Africa and Asia for decades but unknown in the Americas until 1999, is spread to humans by the bite of an infected mosquito. The virus is not transmitted from human to human, or from birds to humans.

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 encephalitis when infected.

If detected early, the virus can be diagnosed and the symptoms treated before serious infections result.

The virus stops spreading when temperatures fall below 55 degrees F (13 C) and mosquitoes become dormant, but can spread again when the insects become active in spring and when birds carry it as they migrate.

Kathryn Converse, a wildlife disease specialist with the U.S. Geological Survey's National Health Center in Madison, Wisconsin, said a study of crows in captivity revealed the the virus could be spread within the same species of bird.

Converse noted that the virus had a 100 percent fatality rate in the crows used in the study.

Health officials noted that the risk of acquiring West Nile virus in humans was "very low," and could be reduced further if people used mosquito repellents and eliminated pools of standing water where mosquitoes breed.