WASHINGTON -- A public health plan is in place nationally to combat further spread of the mosquito-borne West Nile virus, which caused an outbreak of encephalitis in New York City last year, U.S. health officials say.
Despite the effort, there is no guarantee against new cases, the officials said at a recent news conference.
"We may see some cases here and there this year," but no one knows when and where the West Nile virus will strike, said Stephen Ostroff, who is coordinating the West Nile effort for the Department of Health and Human Services.
Last year, the virus caused seven deaths and 62 cases of encephalitis in the New York City metropolitan region.
The virus is believed to have unknowingly infected as many as 1,900 residents of the borough of Queens who did not develop encephalitis, which is an inflammation of the brain and central nervous system.
Federal officials have virtually ruled out the possibility that the West Nile virus was deliberately introduced into this country as an act of bioterrorism, Ostroff said.
When the West Nile virus was first detected in the New York City outbreak last fall, "there were a variety of federal agencies that were very concerned about bioterrorism, and some conducted investigations at that time," said Ostroff, an epidemiologist at the Centers for Disease Control and Prevention in Atlanta.
No agency concluded that "there was a serious likelihood that this is how this occurred, and I don't believe that any agency is seriously considering it at this point," Ostroff said.
Investigations were conducted even though bioterrorism was considered unlikely, because most experts had put West Nile low on their lists of possible biological warfare agents.
Nevertheless, some concern reflected the fact that a sample of the virus had been sent to Iraq a decade ago for diagnostic purposes before the extent of Iraq's biological warfare program was detected.
Ostroff said the West Nile virus from New York was not the same West Nile virus that had been sent to Iraq.
Scientific studies performed over the winter showed that the West Nile outbreak in New York City closely mirrored an outbreak in Romania in 1996 and that the strain of virus was very similar to one identified in geese in Israel in 1998.
"This is not a strain that someone would have had 10 years ago in their collection and that would have been sent elsewhere," Ostroff said.
The Centers for Disease Control and Prevention is the federal agency responsible for tracking infectious diseases. The agency has given grants totaling $2.7 million to 19 state and local health departments to help develop surveillance to detect the West Nile virus in mosquitoes, birds and humans. The aim is to shorten the time between the onset of illness and the diagnosis of West Nile encephalitis.
The agency has developed standardized laboratory tests for West Nile virus and has trained workers in the 19 state and local health departments to perform the tests.
Because birds are the primary source of West Nile, the states receiving the grants are mainly along the flyway of migratory birds along the Atlantic Seaboard.
The states have varying capabilities, and federal officials will help states that do not have facilities to test dead birds for West Nile, said Robert G. McLean, who directs the National Wildlife Center at the U.S. Geological Survey in Madison, Wis.
Federal and state health workers have tested about 1,200 birds found dead last year for the West Nile virus. A crow found in Baltimore was the only bird outside a 75-mile radius of New York City found to be infected, McLean said, and scientists have not determined whether the bird was infected in New York and flew to Baltimore or was infected in Maryland.
None of about 300 birds found dead since Jan. 1 were infected, McLean said.
In addition, blood from 1,300 live birds from 13 states is being checked for West Nile. Tests have been completed in about half, and none was infected, McLean said.