Avian Flu: What Clinicians Need to Know

Emma Hitt, PhD

January 29, 2004

Jan. 29, 2004 — At least eight people in Asia have died from the recent outbreak of A(H5N1) avian influenza, reported Julie Gerberding, MD, MPH, director of the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, speaking at a press conference this week.

In all, 11 cases of human avian influenza infection have been confirmed, most of them in children, in Vietnam (8 cases) and Thailand (3 cases). All but 3 of these cases have proven fatal, with 6 deaths in Vietnam and 2 in Thailand.

So far, avian influenza has shown no signs of being transmitted from person to person; however, the World Health Organization (WHO) notes on its Web site that the rapid spread of highly pathogenic avian influenza among animals, including chickens and migratory birds, "is historically unprecedented and of great concern for human health as well as for agriculture."

Furthermore, as Shigeru Omi, MD, PhD, regional director of the Western Pacific Regional Office of WHO warned, "There's always potential for this kind of outbreak to result in a serious global pandemic, which involves not hundreds, but could kill millions of people globally."

The H5N1 virus has jumped the species barrier into humans on 2 occasions in the recent past. In 1997, 18 persons in Hong Kong were hospitalized and 6 of them died. The second outbreak occurred in February 2003, when a father and son from Hong Kong were infected after travel in southern China; the father died but the son recovered. The source of infection in all of these cases was traced to contact with diseased birds or live poultry markets.

"Right now, the risk here appears to be very low, but we are taking a number of steps because this could be a very serious problem if the epidemic in Asia is not contained," Dr. Gerberding said at the press conference.

David A. Halvorson, DVM, an avian influenza expert at the University of Minnesota in Saint Paul, agreed that the risk of this avian influenza strain getting into the U.S. is not great, because we do not import live poultry from Asia.

"Containment will depend on accurately identifying the methods by which the virus is moving about — it's unlikely to be spreading primarily by migratory birds — and then controlling them," Dr. Halvorson told Medscape. "In our experience with avian influenza, people and equipment are responsible for spreading [the virus] about from farm to farm."

So far, cases of avian flu, mostly in chickens and ducks, have been reported in Japan, South Korea, Vietnam, Thailand, Cambodia, Taiwan, Indonesia, Pakistan, Laos, and China.

According to the CDC, no indication exists for a travel advisory to Americans traveling to affected areas, "but it is important that people who travel to countries that have confirmed poultry cases...avoid contact with poultry farms,...stay away from the markets where live animals are marketed for the food supply, and...avoid contact with items or surfaces that may have been contaminated with excrement from an infected bird," the CDC's Dr. Gerberding said.

The agency is also alerting U.S. clinicians to take a careful travel history of anyone presenting with influenza-like illness and asks people who have traveled to affected areas to remind their clinicians of their recent travel history if they have flu or flu-like illness.

Dr. Gerberding pointed out that the strain of avian influenza involved in this outbreak appears to be sensitive to oseltamivir, which is used for the treatment of H3 influenza circulating in the U.S. "And so, fortunately, that will — may — offer some protection as a prophylactic agent in certain high-risk situations or possibly even benefit individual people who are ill with the disease," she said.

Marguerite Neill, MD, chair of the Infectious Diseases Society of America's Bioterrorism and Emerging Pathogens Workgroup, told Medscape that compared with previous outbreaks, this outbreak of avian flu "has caused more farms to be affected, and the transmission appears to be happening simultaneously across Asia — so whatever is causing the spread is not being controlled."

And while the strain does not appear to be spread through person-to-person contact, the epidemic among poultry allows more and more opportunities for this situation to occur, Dr. Neill explained. "All it will take is the right recombination event between the H5N1 strain and a coexisting human influenza strain."

"This is a very scary situation," Richard J. Webby, PhD, an influenza specialist in the Department of Infectious Diseases at St. Jude Children's Research Hospital, told Medscape in a phone interview. "If a pandemic develops, it will probably be the most significant one since the last flu pandemic in 1968," he said.

Dr. Webby added that the 1997 outbreak in Hong Kong was able to be contained due to the destruction of all the poultry in that country. "But this virus has already spread among poultry throughout Asia, which makes it much more difficult to contain. That's why this will be a lot harder to control," he explained.

"It is hard to estimate whether this strain will jump species, but the flu virus is adaptable, and it certainly wouldn't surprise me if the H5N1 strain finds a way to do that," Dr. Webby said.

Dr. Neill, who is also associate professor of medicine at the Brown University School of Medicine in Providence, Rhode Island, recommended that, more than ever before, physicians should maintain the "respiratory etiquette" protocol that the CDC recommended for the recent severe acute respiratory syndrome outbreak.

This protocol includes instructing persons with symptoms of a respiratory infection to cover their nose and mouth with a tissue when coughing or sneezing; making hand hygiene products and tissues available in waiting areas; providing designated containers for disposal of used tissues; and offering masks to symptomatic patients.

Dr. Neill emphasized that in the face of a possible pandemic of highly lethal flu, "physicians cannot afford to become complacent with regard to respiratory illness."

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