West Nile Virus: The Missing Bird-Human Link

New York City isn't exactly an oasis for wildlife, but its public-health officials are all too familiar with zoonotic diseases, which jump from animals to humans. Ten years before H1N1 erupted among students and killed a principal at an intermediate school in Queens, N.Y., another mysterious illness sickened elderly New Yorkers, sending medical experts scrambling for an explanation. It was August 1999, and several patients at Flushing Hospital were suffering from fever, severe muscle weakness, and confusion. The symptoms didn't add up to a clear diagnosis. "Nothing jumped out at us," Dr. Marcelle Layton, then a New York City Health Department physician told +++NEWSWEEK at the time [[www.newsweek.com/anatomy-outbreak-168190]]+++, "except that many of them were older adults who spent time outdoors in the evening." Blood tests initially indicated that the illness was St. Louis encephalitis, a common form of viral encephalitis transmitted by mosquitoes. Early in September, after several patients died, Mayor Rudy Giuliani announced an all-out attack against mosquitoes. Tabloid headlines screamed: "Let Us Spray!"

It wasn't quite that simple. As trucks and helicopters started getting the pesticide out, Dr. Tracey McNamara, then head pathologist at the Bronx Zoo, was desperately trying to figure out why crow carcasses were turning up on zoo grounds. Dissections she conducted revealed heart lesions and brain hemorrhages, but what was causing the disease? That Labor Day weekend, after several of the zoo's rare birds died—including a cormorant and three Chilean flamingos—McNamara became convinced that an infectious agent was running wild, and that there might be a connection between the birds and the mosquito-borne illness in humans. In an interview with NEWSWEEK's Claudia Kalb, McNamara, now a professor of pathology at Western University of Health Science's College of Veterinary Medicine in Pomona, Calif., recalls how the Centers for Disease Control and Prevention reacted to her theory, and how wildlife surveillance within the United States still needs major improvement. Excerpts:

Kalb: The animal and human investigations conducted during that summer of 1999 took place independently of each other, but you sensed a connection. What happened?

McNamara: That's why I called the CDC. But at the time, there was a real schism between veterinary medicine and public health or human medicine. They categorically denied that there could be any link between the birds and human deaths. They told me I was just dealing with some veterinary thing and there was no possible relationship between the two events.

What did you do?

It was an uphill battle with the CDC until I contacted USAMRIID [the U.S. Army Medical Research Institute of Infectious Diseases] in Ft. Detrick [Md.] and sent them tissue samples. Then the Army called the CDC and said something like, "Guess what? The bimbo's not out of her mind."

What other problems did you run into?

The bigger point that gets lost in this whole story is that crows had been dying since early June, but the disease wasn't quickly and correctly diagnosed by state wildlife officials. Why? Wildlife are free-ranging so losses aren't immediately noticed and it can take quite a few deaths before an investigation is launched. Second, until just recently, disease diagnosis wasn't a mandate of state wildlife agencies and it isn't their forte. Third, labs are terribly underfunded and staff may not even be required to have actual training in diagnostic pathology. Put those all together and you have a real vulnerability as far as surveillance goes. I told the folks in Ft. Detrick that if I were a terrorist looking to introduce a disease to the U.S., the logical place to start would be wildlife.

How did that delay affect the spread of the virus?

There's no doubt in my mind that we would have been able to avoid human deaths in mid-August had a diagnosis been achieved [in the birds] in early June. We would have been able to stop the spread before the mosquito population exploded. It was a missed opportunity.

Why isn't wildlife surveillance better?

Human health is first and foremost [in terms of priorities] and most heavily funded; then agriculture. Wildlife is a tiny dot on both counts. No one owns wildlife, therefore it isn't anyone's problem, so it gets neglected and ignored. Some states have no wildlife lab at all. Until something is done to change that, we will always miss early warning signs in wildlife species. What makes me crazy is that the Europeans are leaving us behind in the dust. They're building a pan-European wildlife disease surveillance network and developing technology to detect both known and novel zoonotic threats. That's the most exciting thing I've seen in 10 years. It's exactly what we should be doing in the U.S.

What about the government's new +++Emerging Pandemic Threats program [[TK LINK TO CLAUDIA'S PIECE]]+++. Won't that help?

My point is that if we're doing that work overseas, why aren't we talking about doing something similar here in the U.S.? We missed monkeypox [in 2003] until it infected people in four states. We use taxpayers as sentinels. Instead of shifting our focus to early warning and detection prior to spillover in the human population, we wait until we have sick people. We respond to a crisis. Being proactive is not in our genes.

Has any progress been made when it comes to domestic outbreaks?

We sat down with the CDC in 2002 and suggested that we needed to leverage the power of zoos. Zoo animals are the ideal urban sentinels for emerging threats, for all the reasons I found. Based on that, we set up a +++network of zoos throughout the U.S. for West Nile Virus surveillance [[www.zooanimalhealthnetwork.org]]+++ and have successfully found the virus ahead of public-health officials for several years in a row. That network has now been expanded to look for H5N1 [bird flu]. And it is being built to be expanded to all zoonotic threats.

What do you think would happen today if you made that same 1999 call to the CDC?

I don't think they'd hang up on me. But we still have that question of who's in charge of zoonotic diseases? The answer's still unclear. We don't have a national plan for zoonotic disease outbreaks. There is a lot more good will between veterinary and public-health entities, but from a practical point of view, little has changed. We have a long way to go.