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Three birds from the captive collection at the US National Zoo in Washington DC have tested positive for West Nile Virus -- two flamingo chicks and a Eurasian wigeon (duck). The zoo is awaiting results from Cornell University's Diagnostic Lab on 12 more birds in their captive collection that have died since early July (5 flamingos, 3 smew, 2 mergansers, 1 blue-winged teal, and 1 wigeon).

A WNV-positive dead crow was found near to the zoo, on Connecticut Avenue, May 1, 2002 and more than two dozen WNV-positive crows have been found since in the nearby area, including 3 WNV-positive crows on zoo property. Most of the crows have been found west of Rock Creek Park, along Connecticut Avenue. Last year, in 2001, 3 mosquito pools and 357 WNV-positive birds were found in Washington DC, mostly in the NE quadrant of the city.

Zoo veterinarians are vaccinating other birds in their captive collection (approximately 300) with the experimental equine vaccine that they have already used on the zebras and tapirs at the zoo. For more information about vaccines being used and developed for West Nile Virus see http://www.cfe.cornell.edu/erap/WNV/default.cfm#vaccine.

The zoo has also installed mosquito traps and is using bacillus larvicides in the zoo ponds.

[This summary is compiled from ERAP's WNV Updates and the following article from the Washington Post.]

The West Nile virus killed two flamingo chicks and a duck at the National Zoo this month and is suspected in the deaths of a dozen other captive birds there, but health officials said yesterday that people have only a tiny risk of contracting the disease.

The dead birds are the first victims of West Nile virus in the zoo's captive population, though the virus has killed hundreds of wild crows in the District since it was first reported in the United States in 1999. The virus also has killed birds at other zoos, including in Atlanta, Philadelphia and New York.

The virus is spread by infected mosquitoes. Humans can get it from a mosquito bite but not from another person. Health officials emphasize that only a small fraction of mosquitoes are infected and that fewer than 1 percent of people who get infected become severely ill.

"The chances of being infected are very, very minimal," said Peggy Keller, chief of the District's animal disease prevention division. "We've had no human cases reported in the city. . . . It's certainly nothing to be alarmed about."

No human cases of West Nile have been reported in the Washington region this year. Since its arrival, the disease has killed 18 people in the United States, including two in Maryland, and made about 150 others seriously ill. The virus is present in more than two dozen states in the East, Midwest and South.

In hopes of preventing more bird deaths, the zoo's veterinarians are vaccinating the 300 or so in their captive collection with an experimental equine vaccine that was used on zebras and tapirs. Zoo staff stepped up precautions this year, installing mosquito traps and using mosquito-controlling bacteria in zoo ponds. They already were draining ponds frequently, aerating them when possible and eliminating areas with standing water, zoo spokesman Robert Hoage said.

Birds, especially crows, are the disease's main victims. It also has been found in horses, cats, bats, chipmunks, skunks, squirrels and domestic rabbits.

In the District, 26 wild crows have tested positive for the virus this year, including three at the zoo. Keller said West Nile cases this year have been concentrated west of Rock Creek Park, along Connecticut Avenue. Last year, when 360 crows died, the high-virus area was in and around Brookland, in upper Northeast. But Keller said people should take precautions throughout the city.

Keepers at the National Zoo found their first dead crow in late June. When a second one was found a day later, zoo pathologists sent tissue samples to be analyzed at a Cornell University lab designated by the federal Centers for Disease Control and Prevention to test zoo birds. The zoo is one of 100 nationwide to participate in a CDC-funded virus surveillance program. Zoo officials in New York, Philadelphia and Baltimore said yesterday that there have been no West Nile cases this year among their captive populations.

The first dead flamingo chick, a month-old bird whose downy gray feathers had not yet become pink, showed up July 6, said the zoo's associate pathologist, Donald K. Nichols. A second chick died three days later. Nichols suspected West Nile when he sent tissue to Cornell to be analyzed and to another facility to have slides made so that he could look at them.

When the flamingo slides arrived July 11, "I thought, 'Ooh, this looks like West Nile,' " he said. Under the microscope, he could see the spread of cells that suggest inflammation, which ruled out bacteria or a fungus. It did not look like herpes, another type of virus that attacks birds.

By then, Nichols was calling Cornell twice a day to find out whether his tissue samples had been analyzed -- "I made a thorough pest of myself" -- and late Tuesday, the diagnosis was confirmed.

So far, Cornell has confirmed that West Nile killed the two flamingo chicks and a Eurasian wigeon. The lab has not yet reported results on a dozen other dead birds -- five flamingos, three smew, two mergansers, a blue-winged teal and a second wigeon -- but zoo officials believe they also died of West Nile virus.

Health officials say the old, the young and people with suppressed immune systems are most vulnerable to the virus. The city's advice is to stay indoors at dawn, dusk and early evening, when mosquitoes are most likely to be out. Everyone, city officials advise, should use mosquito repellent and control mosquitoes around homes.

According to the CDC, "most infections are mild, and symptoms include fever, headache and body aches, occasionally with skin rash and swollen lymph glands. More severe infection may be marked by headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, paralysis and, rarely, death."

Despite reassurance from health officials, Diane Derby said she is concerned about the number of dead crows in her neighborhood of Woodley Park, near the zoo. She saw two while walking her dog.

Derby, a newcomer to the area, said neighbors informed her that Woodley Park is "a hot zone" and that they are "used to seeing dead crows in this time of the season."

That news troubles her. "It is only fair to be concerned when you keep seeing dead crows on the street and when you know that these birds have been killed by a virus that can be transmitted to you by mosquitoes," Derby said, "especially when there is a high concentration of mosquitoes around you."