The CDC heads to Vietnam to assess pandemic threat

H5N1 avian flu kills 12 in Vietnam

Concerned about the emerging threat of pandemic influenza in Vietnam, the Centers for Disease Control and Prevention (CDC) has dispatched a team to Hanoi to investigate an H5N1 avian flu outbreak that had claimed 12 lives as of Jan. 15, 2003.

In the United States, the CDC has issued an alert for enhanced surveillance of possible incoming cases. State and local health departments, hospitals, and clinicians should look for patients who have been hospitalized with unexplained pneumonia, acute respiratory distress syndrome, or severe respiratory illness and who have traveled to Vietnam, South Korea, and Japan within 10 days from onset of symptoms.

Since the end of October 2003, 14 people (13 children and one adult) in Vietnam have been admitted from surrounding provinces to hospitals in Hanoi for severe respiratory illness.

Among the 14 patients, three (two children and one adult) have had avian influenza A (H5N1) virus infections confirmed by testing conducted at the National Institute of Hygiene and Epidemiology in Hanoi and in Hong Kong. Twelve of the patients, including 11 children and the mother of one of the deceased children, have died.

A near miss of a global influenza pandemic involving a strain of H5N1 occurred in Hong Kong in 1997. In that outbreak, fatal infections occurred in otherwise healthy people and H5N1 was transmitted to at least two health care workers before it was stopped.

In 1997, 18 people were hospitalized and six died. Last year, two residents of Hong Kong who traveled to China acquired H5N1 infections and one of them died. Flu experts predicted the avian strain would appear again because it has a reservoir in the wild bird population.

Vaccine work under way

Raising the specter of pandemic flu, the World Health Organization (WHO) reports that network laboratories immediately will begin work on the development of a strain that can be used to produce a vaccine. WHO has initiated the development of candidates and reagents for vaccine production, plus antigenic and genetic assessments of the H5N1 strain to provide up-to-date diagnostic tests to national influenza centers.

The H5N1 strain implicated in the outbreak has been partially sequenced. All genes are of avian origin, indicating that the virus that caused death in the three confirmed cases had not yet acquired human genes. The acquisition of human genes increases the likelihood that a virus of avian origin can be transmitted readily from one human to another. Investigations are focusing on the source of infection and possibilities of human-to-human transmission.

Staff from the CDC will travel to Vietnam to work with WHO and Vietnam’s human and animal health authorities to evaluate the situation, including patterns of transmission of the H5N1 viruses. Dubbed "chicken ebola" for its deadly effect on farm poultry, the avian strain also has stricken farms in Vietnam. In December 2003, an outbreak of H5N1 was reported among poultry in South Korea. In January of this year, Japan reported the deaths of 6,000 chickens on a single farm due to H5N1 infection. No human cases of infection with the avian influenza virus have been reported in either of those outbreaks.