Avian influenza A(H5N1) in humans - update 12
29 January 2004
Prevention of further cases of H5N1 disease in humans
In response to outbreaks of highly pathogenic H5N1 avian influenza in poultry, several countries are currently conducting the mass slaughter of millions of chickens. Such action is the major line of defence for preventing further human cases of H5N1 infection and possibly averting the emergence of a new influenza virus with pandemic potential.
WHO continues to stress the need for personal protection of these workers, who are at high risk of exposure to a virus that has demonstrated its capacity to cause severe disease and deaths in humans. Recommendations about safety measures that should be in place before the mass destruction of poultry begins have been issued. Adherence to these recommendations will reduce the likelihood that measures aimed at preventing the further spread of H5N1 infection in poultry might lead to increased transmission of the virus to humans.
Those organizing culling operations in affected countries need to ensure that WHO recommendations are followed as strictly as possible. The recommendations spell out the appropriate personal protective equipment, which includes goggles and preferably N95 respirator masks, as well as specific types of protective clothing that can be either disinfected or discarded after use. Frequent handwashing is strongly recommended.
WHO also recommends that effective antiviral drugs be readily available for the treatment of suspected H5N1 respiratory infections in cullers and farm workers.
N95 masks and prophylactic treatment with antiviral drugs were used to protect thousands of poultry workers and cullers during an outbreak of highly pathogenic H7N7 avian influenza in the Netherlands in 2003. During that outbreak, nearly 30 million poultry were destroyed. Although avian influenza virus caused mild illness in 89 poultry workers and members of their families, the single death in that outbreak occurred in a veterinarian who was not adequately protected.
Investigation of the origins of the current outbreaks in poultry
Countries currently experiencing outbreaks of highly pathogenic H5N1 avian influenza in poultry have provided numerous samples and viruses to laboratories in the WHO Global Influenza Surveillance Network. WHO is grateful for the high level of international collaboration of all affected countries and influenza experts around the world.
Laboratory characterization of several viruses from humans and different species of birds has helped to compare, retrospectively, H5N1 viruses taken from infected birds and humans in January 2004 with viruses obtained from birds several months ago. Results indicate that the virus now causing severe disease in poultry and some humans has been circulating in parts of Asia for longer than initially presumed.
Presently available evidence from these studies is not sufficient to support any speculations about the geographical origins of the current outbreaks of highly pathogenic H5N1 avian influenza.
Up to now, laboratories in the WHO network have analyzed viruses from the current outbreaks made available by authorities in Cambodia, Japan, South Korea, and Viet Nam. Viruses from the outbreaks in Indonesia, Laos, and Thailand are expected to be available for analysis soon.
Avian influenza A(H5N1) - update 13
30 January 2004
China confirms spread of infection in poultry
Health and agricultural authorities in China have today informed WHO of further outbreaks of highly pathogenic H5N1 avian influenza in poultry. The outbreaks, which are laboratory confirmed, have been detected in Hunan and Hebei provinces.
A confirmed outbreak of highly pathogenic H5N1 avian influenza at a duck farm in Guangxi province was announced on 27 January.
As announced today, outbreaks of disease in poultry have also been detected at farms in Anhui, Shanghai, and Guangdong provinces. According to the authorities, highly pathogenic H5N1 avian influenza is the suspected cause. Samples from birds in these outbreaks are being tested, in China, to confirm the causative agent.
Local authorities in the affected provinces have undertaken immediate culling operations and quarantining of farms. Compulsory vaccination of poultry is being introduced.
At present, no human cases of H5N1 infection have been detected in China.
Development of an H5N1 vaccine for humans: need for samples and viruses
With the confirmed spread of H5N1 infection in poultry in China, WHO is again stressing the need for access to samples and viruses from all countries currently experiencing H5N1 outbreaks. Such materials are needed to support laboratory studies being conducted by the WHO Global Influenza Surveillance Network.
Up to now, laboratories in the WHO network have analyzed viruses from the current outbreaks made available by authorities in Cambodia, Japan, the Republic of Korea, and Viet Nam. Viruses from the outbreaks in Indonesia, Laos, and Thailand are expected to be available for analysis soon.
Network laboratories are now working to develop a prototype virus that can be recommended by WHO for use by companies in the production of a human vaccine effective against H5N1 influenza strains. Both human and avian viruses are needed. Information from these viruses will help WHO and its partners ensure that a fully tested and licensed vaccine for humans is available as soon as possible.
Protection of workers involved in culling operations
As more countries announce plans for the mass slaughter of poultry, WHO continues to stress the need for personal protection of these workers. Targeted administration of seasonal influenza vaccine to high-risk groups, such as cullers and poultry workers, is being recommended as one of several measures that reduce opportunities for the emergence of a new influenza virus subtype with pandemic potential. Guidelines for the use of seasonal influenza vaccine in humans at risk of H5N1 infection have been issued today.