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Public Health Experts Work Together to Address Threat of Avian Influenza

September 29, 2005

A virulent strain of avian influenza (H5N1), deemed by the World Health Organization to be "the most serious known health threat facing the world," could be heading to North America. "Bird flu" has already killed 59 people of 115 confirmed cases in Southeast Asia since the end of 2003 and recently spread to Mongolia, Tibet, Siberia and Kazakhstan. Should this influenza spread to North America -- by the movement of infected people, poultry or wild birds -- it could have a significant impact on Californians.

DucksTuesday, September 28, 2005, UC Davis experts in human medicine, wildlife health and poultry health offered a user-friendly media briefing on what bird flu is, why it is a danger to people, and what the university is doing both to prepare for and help prevent the spread of this serious strain of influenza in the state.

Speakers included:

* Warner Hudson, physician and clinical faculty member at the UC Davis Medical Center, who is an expert in occupational medicine and public health, including infectious diseases.

* Carol Cardona, veterinarian, associate professor and Cooperative Extension poultry veterinarian in the UC Davis School of Veterinary Medicine, who is an expert in surveillance for and detection of avian influenza in domestic poultry. She also conducts research as a member of the National Center for Foreign Animal and Zoonotic Disease Defense.

* Walter Boyce, veterinarian, professor and director of the Center for Wildlife Health in the UC Davis School of Veterinary Medicine, and an expert in disease transmission among wild birds and other animals.

*Howard Backer, physician and interim state public health officer for the Department of Health Services


Avian influenza is an infectious disease of birds that was first identified in Italy more than 100 years ago. It now is found worldwide. Wild waterfowl and shorebirds, particularly ducks and geese, commonly carry various strains of avian influenza but are not usually killed by it. However, wild birds have been implicated in the spread of flu to domestic birds, especially domestic ducks, chickens and turkeys. In domestic birds, avian influenza can make birds very sick and even kill them. Avian flu has also spread to domestic pigs and zoo tigers and leopards in Asia.

The very serious strain of avian influenza (designated H5N1) currently circulating in Asia was first diagnosed in a person in Hong Kong in 1997, and 59 people in Southeast Asia are known to have died from it since late 2003. These deaths have sparked concern that a pandemic (worldwide) influenza could develop.

Scientists believe that the conditions of animal agriculture in Asia have given rise to opportunities for the flu virus to spread among domestic poultry and to new species, including humans. The epidemic of avian influenza in domestic poultry in Asia has resulted in an estimated 130 million poultry deaths and with them, economic devastation in the affected nations. Although most poultry are not raised under the same conditions in the United States as they are in Asia, fears that the epidemic could spread here have sparked questions about programs in the U.S. for surveillance and prevention, and about potential economic impacts.

In people, human influenza virus is a regular seasonal health problem. Every year it kills about 36,000 people in the United States. Much of its persistence and severity is due to its extraordinary ability to mutate, or genetically rearrange itself.

Today scientists and health officials are very concerned that an avian influenza virus and a human influenza virus could combine into a new, very dangerous virus -- one that could have a high death rate and could also spread between people easily. Were such a virus to emerge, it could cause a pandemic rivaling the great influenza pandemic of 1918-19, which killed 40 million to 50 million people.


Dr. Boyce began the session with an explanation that avian influenza is a disease of wild birds, primarily waterfowl, which are natural hosts and carriers of the virus. Typically, these "reservoirs" of avian flu do not become ill with disease. Concern arises because some avian viruses have jumped species, infecting pigs, chickens or people. One strain, the H5N1 strain is "at the top of the news," according to Boyce, because it has also killed wild birds. Boyce stated and other experts repeated that these events are taking place in Asia; no avian flu exists in wild birds of North America. Due to migratory patterns, however, specialists worry that birds could spread the virus around the world.

Boyce concluded by saying that the Wildlife Health Center is part of a large surveillance effort to track avian viruses. About 1,000-2,000 birds are expected to be tested over the next six months, particularly waterfowl such as ducks and geese. The center's field biologists already have begun trapping and sampling live ducks, and will be sampling dead birds at hunter check-in stations. Annual bird die-offs will also be investigated. This sampling would serve as an early warning so that biosecurity measures, primarily in commercial poultry operations, can be strengthened. He added, "There is no justification for killing wild birds" as a prevention strategy. 

Dr. Cardona described the role of poultry--commercial poultry and privately owned birds--in a possible epidemic. "There are many human health concerns that existing virus, now an epidemic in domestic poultry in Asia, could become a human pandemic," or world-wide epidemic, she explained. Cardona stated that U.S. and Asian methods of raising poultry are "mostly done in a vastly different way," with Asian ducks, chickens and people living in close proximity while U.S. poultry farms tend not to mix different types of birds. U.S. producers already have biosecurity measures in place on their farms that exclude many outside contaminating factors. "Biosecurity is a very effective measure," Cardona said, giving the example of Singapore as a country that has so far escaped the avian flu problem by protecting domestic birds from contact with wild species. 

"The United States is committed to remaining "influenza-free," Cardona said, with regular testing of commercial flocks as a way to keep tabs on the presence of disease. The U.S. does not employ vaccination as a prevention strategy. She stated that surveillance of backyard birds is also ongoing, with owners well aware of risks to their birds as a result of building relationships with agricultural health officials during an outbreak of exotic Newcastle disease in 2003. Cardona emphasized the positive role of education regarding risks and biosecurity.

Dr. Hudson opened with the remark, "We need to prepare because we're uncertain." One strain of avian flu, H5N1, has been lethal in humans. This or related avian flu viruses could therefore become transmissible to humans. He noted that of the three worst human influenza events, "We're sure that at least two involved avian flu. This is the first time we've had an early warning. We're in better shape than previous generations as far as preparedness. We have a chance to plan."

Hudson explained that UC Davis is conducting influenza surveillance on the human side. "The state is ramping up on the public health side, polishing up plans to respond." While extensive quarantine and isolation would take place during an epidemic, basic preparation now for consumers, he said, involves basic hygiene and getting an annual flu shot.

Dr. Backer began with a chilling statement that, if a pandemic of influenza were to strike the United States, as many people might die in California as now die in the entire country all year.

Risk factors that alert public health officials, he said, include the fact that the H5N1 subtype is a novel virus, which means that humans have little or no immunity from previous exposure. It has already caused disease in people. However, so far the disease is not easily spread from person to person.

Today, Backer is emphasizing coordination with regional health departments, hospitals, health plans, universities and state agencies for prevention. A surveillance program exists at the state level. Backer reported that about two dozen possible cases have been tested at the state's health lab in Richmond and ruled out avian influenza. "At the California Department of Health Services, preparing is similar in preventing a disease outbreak or responding to a bioterrorism event. Hospitals are preparing labs, equipment, and standards for 'surge' capacity, or receiving high numbers of patients at once. We need to reach out because of the scale of this possible problem."

Individuals, he stressed, should begin now to engage in "healthy behaviors" such as flu shots, hand-washing, covering coughs and remaining home when sick to reduce the spread of illness.

Backer said that while vaccines exist for annual flu shots based on current strains of the virus, experts are hesitant to develop and stockpile a vaccination for another strain that might evolve further. Flu vaccines based on a particular viral sub-type do not provide cross-protection for newer or re-emerging strains.

He commented that if the avian flu does arrive, via birds or--as likely--human travelers, "Our hope is that pathogenicity may decrease as it enters and/or mutates into humans." Regarding the likelihood of a pandemic, Backer said, "I have no crystal ball, but it would be foolhardy not to prepare for early intervention."

Backer emphasized new and creative partnerships as well as traditional working relationships among public health practitioners. "We work with veterinarians in the health department because so many diseases are transmitted between animals and people." 

The information above comes from News Service advisories and the School of Veterinary Medicine.

More information from UC Davis News Service:

UC Davis Experts Vigilant for Avian Influenza

Watching for 'Bird Flu' in California

Questions and Answers about Avian Influenza

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