Note: Myanmar has been removed from the list of countries with confirmed H5N1 outbreaks.

Recent Influenza A(H5N1) Cases

The Government of Vietnam has reported hospitalized cases of severe respiratory illness in people from provinces surrounding Hanoi beginning in October 2003. Avian influenza A(H5N1) virus infections have been confirmed is some of these patients. On January 26, 2004 the government reported its first confirmed cases in the south of the country, with two cases in Ho Chi Minh City . Deaths have been reported.

Beginning January 23, 2004 , the Government of Thailand began reporting cases of avian influenza A(H5N1) infections in humans. Deaths have been reported.

Visit www.who.int/en for updated case counts.

Influenza A(H5N1) viruses normally circulate among wild birds but can infect poultry and rarely have infected people in the past. In 1997, 18 persons in Hong Kong were hospitalized because of influenza A(H5N1) infections and six of them died. In 2003, two residents of Hong Kong who traveled to China developed influenza A(H5N1) virus infections and one of them died. In Vietnam, large outbreaks of influenza A(H5N1) have been reported among poultry in the southern and northern regions of the country. The World Health Organization (WHO) has reported that the H5N1 strain implicated in the outbreak has been sequenced. All genes are of avian origin, indicating that the virus has not acquired human genes. The acquisition of human genes increases the likelihood that a virus of avian origin can be readily transmitted from one human to another.

H5N1 Outbreak Investigation

WHO is coordinating an investigation in Vietnam. Staff from CDC have traveled to Vietnam to work with WHO and Vietnam’s human and animal health authorities to evaluate the situation, including patterns of transmission of the influenza A(H5N1) viruses. The investigation will focus on determining specific characteristics of influenza A(H5N1) viruses isolated from human cases and poultry and on determining how people became infected. In addition, increased surveillance will help investigators determine how many people in Vietnam already have been infected with the influenza A(H5N1) virus and whether other people are continuing to be infected. WHO will be collaborating closely with health authorities in Thailand in responding to the situation there.

H5N1 Infections Among Poultry in Asia

Outbreaks of avian influenza A (H5N1) have been confirmed among poultry in South Korea, Vietnam, Japan, Cambodia, Thailand and China. Additional countries have detected deaths in poultry flocks. The cause of these is under investigation.

CDC Recommendations

U.S. residents who are traveling outside the United States should consult their physician for advice about which vaccines they should obtain. In Vietnam and in other tropical regions, influenza can occur at any time during the year. Thus, persons who are at increased risk of developing influenza-related complications and healthy persons who wish to decrease their risk of becoming ill with influenza should receive the 2003-04 trivalent influenza vaccine. The vaccine will protect against three viruses and offers some protection against variants of them as well.

At this time CDC and WHO have not issued any travel alerts or advisories for the region in response to the H5N1 outbreak. However, travelers to countries in Asia with documented H5N1 outbreaks are advised to avoid poultry farms, contact with animals in live food markets and any surfaces that appear to be contaminated with feces from poultry or other animals. For more information about topics related to travelers’ health, visit www.cdc.gov/travel.

Enhanced U.S. Influenza Surveillance

At this time, CDC recommends enhanced surveillance efforts by state and local health departments, hospitals, and clinicians to identify patients who have been hospitalized with unexplained pneumonia, ARDS, or severe respiratory illness AND who have traveled to countries in Asia with documented H5N1 outbreak.

CDC will make additional recommendations on enhanced surveillance if influenza A(H5N1) activity continues to evolve.

More Information About Influenza

For further details about the reported cases of influenza A(H5N1) in Vietnam, see the WHO Web site www.who.int/en. Additional information about influenza is available on the CDC Web site at www.cdc.gov.