Dr. Tracey McNamara ©WCS   Meanwhile, back in the Bronx... Dr. Tracey McNamara, head pathologist at the Bronx Zoo, began to look harder at the onslaught of sick crows. Single-species die-offs of this kind are rare. Since around August 25th, she had been shipping the dead crows off to offices in Albany, headquarters of the New York State Department of Environmental Conservation. But in the absence of a diagnosis McNamara began to conduct her own dissections, as well as full evaluations of tissues under the microscope. They revealed that the crows were bleeding from the brain and had badly damaged hearts. "These symptoms are characteristic of viral encephalitis, and there are a few kinds in the veterinary world that could account for the mass deaths: exotic Newcastle disease or highly pathogenic avian influenza," noted McNamara. "But in addition to the fact that dead birds didn't fit the classic profile, we had healthy chickens and turkeys in the children's zoo and those would have been the first to die from one of the above two diseases." Another contender was Eastern Equine encephalitis, to which emus are highly susceptible, but the zoo's emus were doing fine. September 4 An epidemiologist at the NYC health department learned of the large numbers of dead birds and informed state health officials and the CDC of a concern that they might be connected to the human deaths. September 8 A puzzled McNamara examined several exotic birds that had died over Labor Day weekend and the week that followed: a Guanay cormorant, three Chilean flamingos, an Asian pheasant, and a bald eagle. Dissections showed the same heart and brain lesions she had found in the dead crows. By this time McNamara knew the illness wasn't bacterial because not one of the 57 cultures she had done since August 1 showed pathogenic [disease-causing] activity, nor was there any evidence of pesticide exposure. Nor was what McNamara was seeing compatible with any known avian viruses. The only species the zoo was losing were birds kept outdoors, and they were primarily North and South American species, which suggested the disease was new to this hemisphere. At this point, McNamara made an intuitive leap. "I don't really care what's in the textbooks," she says bluntly. "It's never a surprise to me to see something unusual, because non-domestic species have never received the same attention as economically important domestic species." The pathologist knew that people were dying at the same time from a known mosquito-borne disease. Experts said a bird-human link was impossible, but, she reasoned, "the fact is that I have barrels full of birds dead from encephalitis, and I've ruled out all the usual suspects." A wildlife pathologist at the NYS Department of Environmental Conservation sent bird samples to laboratories at both the USGS Wildlife Health Center and the USDA/APHIS National Veterinary Services. A cover letter noted that crow deaths are coinciding with a highly unusual human outbreak of SLE. Health officials confirmed the first positive human case outside Queens, in Brooklyn. Other cases were now suspected throughout the city. Citywide mosquito control efforts began. September 9 Two more flamingoes died at the Bronx Zoo. Nervous, McNamara called the CDC in Atlanta to say that she suspected a possible link between the cases of human encephalitis and those of the birds. Pointing out that SLE and related viruses do not normally kill birds, which are natural hosts in other areas, the CDC refused the samples of bird tissue she offered to send them. Work on animals is not part of the CDC mission. They also discussed the possible exposure of a veterinary assistant at the zoo, via a needle-stick. McNamara sent samples from several zoo birds to laboratories at the National Veterinary Services Lab in Ames, Iowa, which is part of the US Department of Agriculture and which immediately agreed to start testing for encephalitis viruses. They swiftly ruled out all the common bird viruses. By Monday morning, four days later, a cell culture showed that the zoo birds and wild crows were dying of the same disease. September 14 The National Wildlife Health center laboratory in Wisconsin isolated a virus from bird samples which tests negative for SLE and eastern equine encephalitis. Virologists discussed the possibility of a new strain of SLE or an exotic disease. September 15 The National Veterinary Services Lab in Iowa confirmed that under an electron microscope the viral particles were only 40 nanometers in diameter. This was decisive. It put the disease in the category of a flavivirus, and possibly a new one: too small to be the likely arborvirus candidates, Eastern or Western or Venezuelan encephalitis. At that point, further characterization of the virus required someone outside the veterinary world, because such flaviviruses had never before killed animals--and because these viruses require containment facilities. They contacted the CDC. Unbenownst to the CDC, Ian Lipkin, a scientist at the University of California at Irvine, was given samples of brain tissue from some of the New York patients by NY State Department of Health officials at a conference in Albany. He began to conduct rapid reverse transcriptase polymerase chain reaction (RT-PCR) testing of the virus's genetic structure. Standard PCR tests conducted in New York City had tested negative for SLE. September 19 After a week with no response from the CDC, an impatient McNamara got in touch with the US Army Medical Research Institute in Infectious Diseases (USAMRIID) in Ft. Detrick, Maryland. Within two days she established a scientific collaboration with USAMRIID scientists. Alarmed, they urged her to send samples immediately, and expressed concern about her possible exposure to a new pathogen. Though disputing the findings of the National Veterinary Services Lab, the CDC requested tissue samples from McNamara.      2 of 4