Avian Influenza A (H5N1) Human Infection in Hong Kong

On November 17, 2010, the Centre for Health Protection (CHP) of the Department of Health (DH), Hong Kong, China, reported a new confirmed case of human infection with avian influenza A (H5N1) virus to the World Health Organization (WHO). More information on the case is available in Communicable Diseases Watch, a publication of CHP DH, Hong Kong, China and on the WHO website.

This case occurs against a backdrop of endemic infection with highly pathogenic avian influenza A H5N1 viruses (HPAI) among poultry in Asia and other parts of the world and sporadic but fairly regular human infections with HPAI H5N1 viruses dating back to 2003. These viruses are “highly pathogenic” in birds. Most cases of human infection with HPAI H5N1 viruses have occurred following close contact with infected birds or being in a live poultry market. However, some limited human-to-human transmission of HPAI H5N1 has been documented.

The epizootic outbreak in Asia and other regions poses an important public health threat because if these HPAI H5N1 viruses gain the ability for efficient and sustained transmission between humans, an influenza pandemic could result because there is little preexisting natural immunity in the human population.

WHO tracks reports of human infections with H5N1viruses. To date, 508 such cases have been reported to WHO, with 302 of the patients dying. So far, a total of 21 human cases of HPAI H5N1 infection have been reported in Hong Kong SAR China, including 18 cases in 1997, two cases in 2003 and the current case in 2010.

The investigation into the case in Hong Kong is ongoing, however, according to the WHO report, “Evidence so far indicates a sporadic case of human influenza A (H5N1) infection without secondary spread.”

There have been no reports of human infection with influenza A (H5N1) viruses in the United States, nor have there been any reports of highly pathogenic influenza A (H5N1) in U.S. birds or poultry.

CDC is monitoring the situation and remains in close contact with WHO and other international partners. More information about avian influenza is available at the CDC avian flu website.

Action Steps Being Taken

The U.S. Government CDC has issued a recommendation for enhanced domestic surveillance of avian influenza A (H5N1). This has been in effect since February 2004 and remains in effect to this day.

CDC has participated in trainings both internationally and at home to strengthen surveillance and laboratory testing techniques.

Pandemic preparedness plans and activities were tested in reality during the 2009 H1N1 pandemic.

HHS and CDC along with other partners such as WHO have implemented important initiatives that have improved influenza surveillance in Asia and other regions of the world.

There is a stockpile of 20 million doses of a vaccine against some strains of HPAI H5N1 viruses. Ongoing efforts to produce a broadly protective vaccine that would be effective against multiple influenza A H5N1 virus strains are under way.

There is a stockpile of antiviral medications to treat human infection with novel influenza viruses, including avian influenza A H5N1 in the Strategic National Stockpile.

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