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West Nile Outbreak Renews Response Capability Questions

A deadly West Nile encephalitis virus strain swept through the New York City area in the late summer and early fall of 1999, claiming seven lives among 56 infected individuals and threatening many others in this densely populated region. It confronted the public with a series of scary images, including a grim scattering of bird corpses and fleets of helicopters spewing insecticidal mists. Perhaps more importantly, the incident raises doubts in some circles about how well prepared local and federal officials are for rapidly detecting and dealing with this or other emergent pathogens, particularly those that bioterrorists might deliver.

To address some of these questions, officials from the Centers for Disease Control and Prevention (CDC) in Atlanta, Ga., convened a two-day meeting in November to evaluate overall response to the West Nile outbreak. Key topics for meeting participants included the need for an integrated plan involving experts from various disciplines and for increased overall surveillance for such outbreaks.

Public health officials and other experts give mixed views about the lessons from the New York incident. In some ways, the West Nile incident demonstrates how the detection and response system can and does work, according to Steve Ostroff from CDC. But, he adds, it also reveals shortcomings that could be remedied in part through advanced technology as well as improved human oversight, better diagnostic capabilities, and the availability of more sophisticated communication networks than are now in use.

One of the chief criticisms of the public health system response in the West Nile case was the lag between when the problem was detected and the virus causing it was precisely identified. It took 11 days to finger an encephalitis virus as the culprit and begin mosquito-control efforts. However, 21 days later, investigators at CDC and two other labs independently reached the same conclusion: the earlier identification of the viral agent was somewhat off the mark: instead of it being the St. Louis encephalitis virus, the West Nile encephalitis was, in fact, to blame for the outbreak.

Ostroff says that the 11-day interval between recognition and the start of control measures was relatively brief. ``There is a misconception that the system didn't particularly perform very well. I don't necessarily see it that way,'' he says. Even though the initial identification of the virus was slightly off, officials instituted appropriate control measures, inasmuch as the St. Louis and West Nile viruses are closely related, mosquito-borne arboviruses. ``I think that the system performed better than most people realize,'' Ostroff says. ``But we certainly are in the quality improvement mode.''

Although some critics focused on the initial misidentification of the virus, Ostroff says that a more important issue is how long the outbreak went on before being detected. CDC investigators now say that the first cases most likely occurred in early August, two weeks before a local clinician alerted health authorities to unusual symptoms in two patients. ``I think one of the questions that needs to be asked is, can we conceivably put systems in place that would have recognized that there was an outbreak even earlier,'' he says.

That would require two elements: appropriate technology and better interactions among disparate agencies and authorities. Ostroff envisions sophisticated electronic technology that could collect and sift enormous amounts of data to pick out unusual symptoms or groups of symptoms and flag them for the attention of public health authorities.

As a near-term response, efforts are being made to enhance communications among agencies, scientists, and laboratories charged with detecting and diagnosing pathogenic agents. The unusual deaths of birds in the New York area could have provided early clues that something was amiss, according to Ostroff. Indeed, a veterinary pathologist at the Bronx Zoo was one of the first individuals to make the link between dead birds and the unusual illnesses striking New York citizens. She reportedly had some difficulties getting a response from CDC scientists after she sent them avian samples.

``It highlights a need for partnerships,'' Ostroff says of this miscue. ``I think as part of any effort to upgrade national capability, it really does require a concerted effort among public health authorities, clinicians, microbiologists, veterinarians, etc., to increase the knowledge and understanding and capability to deal with these agents that don't occur often,'' he says. However, communications are always a challenge in a crisis situation, he says. The West Nile incident ``was a reminder of how challenging that would be in the event of an actual bioterrorism episode where thing may move even more rapidly. Everyone is potentially getting and acting on different pieces of information rather than having the entire picture.''

Christine Stencel
Christine Stencel is a science writer and manager of communications at ASM.