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I wanted to clarify several statements in the article attributed to me. A better term for the establishment of WNV transmission in Florida would have been "endemic" instead of ingrained. A more complete statement about WNV virus in Memphis was that the virus was likely transported there by southward migratory birds from the northern Midwestern states (e.g. Ohio, Illinois, Michigan, Wisconsin, Indiana) where intense transmission was occurring, but not carried there by the 40 blue jays and few crows that were found WNV positive. The jays and crows were more likely the sensitive indicators of the local virus transmission that occurred after the virus was taken there and seeded by other bird species into this metropolitan area along the Mississippi River. The zigzag dissemination of WNV is what I described, but I do not believe that the virus can make it to the west coast this year unless and until there are sources of WNV transmission established (foci) in Central America or Mexico where most of the west coast migrating birds pass during their northward migration. We do not have any knowledge about WNV transmission in Central America or Mexico that I know about at this time, but it could obviously go undetected there for awhile.

Regardless, this virus strain is disseminating rapidly and has become established in locations easily even in temperate climates of the northern states and Canada. As stated by Dr. Berry, reintroduction to the northern states by migratory birds is likely occurring in addition to and on top of spring initiation of virus transmission in locally established foci.

Best regards, Bob

With West Nile virus' rapid colonization of the Midwest and South, researchers are discovering that infections among new species of birds and mosquitoes, varying geography and changing weather patterns are in essence granting one disease multiple personalities.

Although the basic tenets of disease surveillance and control remain intact, many states have been forced to reconsider past strategies, as an evolving disease that likely persists in hibernating mosquitoes and hitches rides with migrating birds has dared public health officials to keep pace.

Meanwhile, dismayed New York health officials say much of the public vigilance - and funding - has followed the virus to new frontiers but flagged closer to home. By June, officials had already collected infected birds from Albany, Rockland and Nassau counties; this is the fourth such year the mosquito-borne virus has delivered its early calling card of dead crows and blue jays. Among most New Yorkers, however, the news has amounted to little more than an irksome rite of spring.

"I have to admit that there may be less of a sense or urgency on the part of the public, and I'm not sure that it's entirely appropriate," said state Health Department spokeswoman Kristine Smith. "It's a combination of people getting used to it, that what we've learned suggests not as many people are at risk for serious illness as we first thought, and there are other things to worry about."

Smith said health officials are "extremely concerned" that a lapse in public vigilance could hinder the state's successful dead-crow reporting system or hamper other surveillance and education efforts. Funds for these educational messages have remained reasonably intact in the state's budget, but the department's laboratory and surveillance efforts will have to make do with less. Last year, New York received $3.9 million in grants from the U.S. Centers for Disease Control and Prevention for such efforts, but the CDC has announced a shift in funding toward new states grappling with the virus, and New York received slightly less than $2 million this year.

Last year, West Nile virus was documented in 27 states and the District of Columbia. This year, it has already appeared in 14, including a new foray into eastern Texas.

Dr. Richard Berry, chief of Ohio's vector-borne disease program, said state officials there had been expecting West Nile's return after the virus began popping up in Illinois and Michigan earlier this spring.

"Nevertheless, it is surprising to see it for the first time," he said of West Nile's regional debut in 2001. "It's a different type of virus and a different type of epidemiology than we're used to."

Although scientists believe West Nile is slightly less lethal to humans than St. Louis encephalitis, West Nile has displayed much more persistence than its North American cousin. Most health officials agree that the early re-emergence of West Nile throughout the Midwest and South this spring indicates the virus' ability to survive in hibernating mosquitoes, a feat first documented in northern Queens after the 1999 outbreak and likely aided by the succession of relatively mild winters since then.

"We may be getting a double whammy here with the virus over-wintering in some species of mosquitoes and it being reintroduced with some migratory birds," Berry said. Both phenomena may be contributing to the unprecedented spread of the virus, experts say.

"We expected it to expand, but it really has gone more rapidly than I had anticipated," said Bob McLean, director of arboviruses at the U.S. Geological Survey's National Wildlife Health Center in Madison, Wis. "The alarming thing is that so many new sites have become sources of the virus. The other big worry is that in places like Florida it can become really ingrained."

So far, the virus seems to be fulfilling the grim forecast. Although West Nile activity in Florida peaked in late September, the state reported infections among horses, birds and sentinel chickens (posted to detect the virus) through December. Florida officials waited until Dec. 31 to remove 53 counties from a medical alert.

Ten days later they collected the first West Nile-infected bird of 2002, a wild turkey in the state's panhandle. CDC grants to the state for increasing lab capacity and surveillance have echoed the concern, with a jump in funding from $200,000 last year to $1.5 million this year.

Among this year's plans, Florida officials hope to beef up the state's sentinel chicken surveillance system, which has met with considerable success, unlike New York's abandoned efforts. Although used less heavily in the hard-hit northern part of the state last year, sentinels tested positive in 20 counties and provided the first warning of the virus in four.

Florida health officials have been considerably less impressed with the utility of the dead-crow- density system deemed successful in New York.

"So far in our analysis, we didn't see the correlation between density and human risk," said Dr. Lisa Conti, a public health veterinarian and epidemiologist for the Florida Department of Health. The disparity may rest with differences in crow, mosquito and human populations between the two states, but officials say even New York's success may be threatened by public apathy or complacency. That fear has only been heightened by the sagging volume in this year's calls to state and local dead-bird hotlines.

Other research groups hope participation-independent programs may provide new surveillance solutions. Bryon Backenson, assistant director of New York State's arthropod-borne disease program, said the state has joined forces with a NASA research group and Oxford University to develop West Nile risk-assessment maps.

Researchers have begun collecting weather and geographic variables from NASA satellites, such as temperature, precipitation, vegetation cover and bird migratory routes. New York added its 2001 West Nile data from bird and mosquito populations. Oxford, with its long history of using similar data to predict the emergence of other arthropod-borne diseases such as dengue, has combined the information to generate maps.

The initial maps appear promising, but Backenson said states may have to fine-tune their surveillance efforts to account for different weather patterns and such factors as which mosquito species make good vectors for the West Nile virus.

McLean, meanwhile, has led a research effort to capture and take blood and feather samples from about 7,000 migratory birds in the past three seasons. Originally focused on sites along the Atlantic Flyway, the researchers have since added trapping sites in Texas and along the Mississippi River to study the Mississippi Flyway, another major migration route.

McLean said birds normally molt, or shed their feathers, at their breeding grounds. The new feathers incorporate the prevailing minerals and chemicals of the area, creating a signature of sorts from where they've been. "So if we pull off a feather from a bird in Florida, and it got the feather in Canada, we can tell that with the signature," he said. If the bird tests positive for West Nile, researchers may begin to get an idea of how - and where - migratory birds may be spreading the virus. Results are expected later this year, but McLean already has his suspicions.

"Memphis is a good example," he said. "They didn't get any virus until mid-September. And all of the sudden they had 40-some positive birds." Those infected birds, he said, likely came from northern locales in the Midwest and spread it south as they migrated.

"I suspect the reverse is happening this year," he said. "The birds are bringing it northward." And since birds have different routes in the spring and fall, the virus could zigzag throughout the United States by year's end.

And in New York?

"It's just amazing to me, because of the temperate climate, that the virus is sticking around," he said. "As we've said before, the virus is writing new chapters here in the States."