World health organizations rush to avoid avian influenza pandemic

World health officials fear that an outbreak of a highly pathogenic strain of the avian influenza virus in Asia threatens to become a worldwide pandemic.

In a joint statement issued Jan. 27, the World Health Organization, Office International des Epizooties, and Food and Agriculture Organization warned that the H5N1 avian influenza strain could mutate into an even deadlier human pathogen.

Since Japan reported an initial outbreak of avian influenza to the OIE in early January, the virus has spread to eight other countries: South Korea, Thailand, Vietnam, Cambodia, Indonesia, Pakistan, China, and Laos. A different viral strain is active in Taiwan.

Vietnam and Thailand have confirmed 23 cases of H5N1 infection in humans, 18 of them fatal. The virus has caused the deaths of millions of birds throughout the affected countries.

"This is a serious global threat to human health," Lee Jong-wook, MD, WHO director-general, said. "But we have faced several emerging infectious diseases in the past. This time, we face something we can possibly control before it reaches global proportions if we work cooperatively and share needed resources."

The WHO, OIE, and FAO have requested donations of funds and technical assistance to affected countries to help eliminate the virus.

According to the U.S. Department of Agriculture, many strains of avian influenza virus exist worldwide and can cause varying amounts of clinical illness in poultry. Chickens, turkeys, pheasants, quail, ducks, geese, and guinea fowl, as well as a wide variety of other birds, are susceptible.

Avian influenza viruses can be classified into low-pathogenic and highly pathogenic forms, depending on the severity of the illness they cause. Most virus strains are low-pathogenic and typically cause little or no clinical signs in infected birds.

In February, a less virulent form of the virus had been detected in poultry flocks in Delaware. Federal and state agriculture officials were working with industry to contain the virus. This low-pathogenic strain of avian influenza isn't a reportable disease under the OIE, nor does it pose a human health or food safety threat. Nevertheless, as of Feb. 9, South Korea, Japan, Singapore, Malaysia, and Poland had banned imports of U.S. poultry products.

The H5N1 strain is a threat to public health, however, if it circulates long enough in humans and farm animals. That would increase chances for the virus to evolve into a pandemic influenza strain that could cause disease worldwide.

"With SARS, we learned that only by working together can we control emerging global public health threats," Dr. Jong-wook said. "Now, we confront another threat to human health and we must reaffirm existing collaboration and form new ones."

In addition, avian influenza can be an economic disaster for the poultry industry. The highly pathogenic strain has the potential to spread quickly among animal populations in developing countries where control measures are difficult to put in place.