(Updated October 2007)
During 2005, outbreaks of H5N1 among poultry were confirmed in Cambodia, China, Indonesia, Thailand, Vietnam, Russia, and Kazakhstan; poultry outbreaks were also reported in Malaysia and Laos during 2004. Since January 2004, 331 human cases of avian influenza A (H5N1) have been reported to date: one hundred in Vietnam, twenty-five in Thailand, seven in Cambodia, and 109 in Indonesia, resulting in 202 deaths worldwide, none of which were in the US. CDC remains in communication with WHO and continues to closely monitor the H5N1 situation in countries reporting human cases and animal outbreaks. We remain in a Phase 3 level of worldwide alert in which there are no (or very rare) documented cases of human to human transmission.
Most cases of H5N1 infection in humans are thought to have occurred from direct contact with infected poultry in the affected countries. Therefore, when possible, care should be taken to avoid contact with live, well-appearing, sick, or dead poultry and with any surfaces that may have been contaminated by poultry or their feces or secretions. Transmission of H5N1 viruses to two persons through consumption of uncooked duck blood may also have occurred in Vietnam in 2005. Therefore, uncooked poultry or poultry products, including blood, should not be consumed.
The threat of novel influenza subtypes such as influenza A (H5N1) will be greatly increased if the virus gains the ability to spread from one human to another in a sustained fashion. Such transmission has not yet been observed; however, a few cases of limited person-to-person spread of H5N1 viruses may have occurred.
A vaccine to protect humans against avian influenza A (H5N1) is not yet available, but one is undergoing human clinical trials.
CDC has not recommended that the general public avoid travel to any of the countries affected by H5N1. Persons visiting areas with reports of outbreaks of H5N1 among poultry or of human H5N1 cases can reduce their risk of infection by observing the following measures:
For more information about H5N1 infections in humans, visit the World Health Organization avian influenza website, the CDC Avian Influenza website, or the Department of Health and Human Services website.