Avian Flu in Asia
15 January 2004
Avian Flu in Asia
The Ministry of Health says New Zealanders travelling in Asia should be alert to World Health Organisation advice of a bird flu outbreak in parts of Asia.
It says New Zealanders travelling to Asia should avoid contact with live poultry, but information from WHO does not suggest any need to avoid travelling to the affected areas.
Dr Doug Lush, Acting Director of Public Health, said laboratory tests have confirmed that three people who died after being hospitalised in Hanoi, Vietnam, had H5N1, a strain of avian influenza (bird flu). H5N1 is also suspected to be the cause of severe illnesses in 11 people in Hanoi and surrounding provinces. In total twelve of those affected have died. There are also unsubstantiated reports of illness in poultry from Cambodia, Taiwan, Indonesia and Thailand.
He stressed that there had been no reports of H5N1 being transmitted from one person to another.
"Evidence shows that poultry are the source of the virus and it may be sensible to avoid live poultry and their excreta. However it is possible that this strain of avian flu could mutate and be transmitted from human-to-human."
"At this stage that is still only a potential risk, although certainly one that international experts are taking very seriously.
"Right now the actual risk for travellers in countries like Vietnam is if they visit markets or other places where there could be infected chickens, and chicken pooh. There is nothing in the information we have at present to suggest any increased risk to travellers who observe the usual precautions about eating hygienically prepared cooked poultry."
WHO says the H5N1 virus, which is fatal in virtually all chickens it infects, has killed about 40,000 chickens in Vietnam so far. The Vietnamese government is culling an additional 30,000 birds in a bid to contain the outbreak.
The same strain killed a large number of chickens and ducks in the Republic of Korea in December 2003, and in parts of Japan. Both countries have set up poultry culls.
Dr Lush said the first cases of humans being infected with avian influenza were identified in Hong Kong in 1997. The virus infected 18 people and caused six deaths. Hong Kong's culling of around 1.5 million poultry is believed to have averted a larger outbreak in humans.
"WHO regards every case of transmission of an avian influenza virus to humans as a cause for heightened vigilance and surveillance. Influenza viruses are highly unstable and if you have animal and human strains circulating at the same time they could "meet" and give rise to a new influenza virus to which humans would have little, if any, protective immunity.
"In New Zealand we have an Influenza Pandemic Plan. We will be maintaining our links with the global surveillance programme, and can activate or update our plan as soon as the information from other parts of the world suggests we should do so," Dr Lush said.
Ministry of Agriculture and Forestry spokesman Dr Hugh Davies said there had been no reports of unusual poultry deaths in New Zealand.
Dr Davies, Director of MAF's reference laboratories, said a special secure laboratory would be used to investigate any such outbreak. He said there was little chance of "importing" the virus as this was not the migratory bird season but MAF plans to survey viruses in migratory birds next season (NZ spring).
For the Ministry of Health pandemic plan go to www.moh.govt.nz and then to publications
For World Health Organisation information on H5N1 go to www.who.int.
Frequently asked questions:
What is bird flu?
Bird flu or avian influenza is a contagious viral infection which can affect all species of birds. In intensive poultry rearing systems young fattening turkeys and laying hens are usually the most affected species. Free-living birds may carry influenza viruses without becoming ill due to a natural resistance. It is known that wild waterfowl present a natural reservoir for these viruses and can be responsible for the primary introduction of infection into domestic poultry.
What causes it?
The virus causing avian influenza is an Influenzavirus A virus of the family Orthomyxoviridae.
Influenza A viruses infecting poultry can be divided on the basis of their pathogenicity (ability to cause disease). The very virulent viruses cause highly pathogenic avian influenza (HPAI) with mortality in poultry as high as 100%. In the whole world there have been only 19 reported primary isolates of such viruses from domestic poultry since 1959. A severe epidemic occurred in Italy in 1999/2000 causing 413 outbreaks with 16 Million birds affected. Other AI viruses cause a much milder disease (low pathogenic avian influenza, LPAI). Signs of sickness are much less evident or even absent and mortality is much lower.
How does it spread to humans?
H5N1 has been caught by people handling poultry in situations such as markets, where they are exposed to both live and dead birds and their faeces. Because of the approach of the lunar New Year, which is significant in many Asian countries, there is a high demand for poultry, and for noodle soup with raw eggs - which travellers should also avoid.
Why is the WHO concerned?
There have now been a number of reported cases of human infection with H5N1. WHO regards every case of transmission of an avian influenza virus to humans as a cause for heightened vigilance and surveillance. It is particularly concerned when there are highly pathogenic avian influenza viruses in large numbers of poultry in a growing number of countries.
Influenza viruses are highly unstable. When they are circulating at the same time as human viruses there is potential for the two to "meet" and create a new influenza virus to which humans would have little, if any, protective immunity.
Which countries are experiencing outbreaks?
An outbreak of highly pathogenic H5N1 avian influenza was detected in southern Vietnam in the beginning of January. The outbreak is now known to have spread to other provinces in the country. Reports indicate that pigs and ducks have also been infected. In mid-January officials in the Republic of Korea announced the spread of H5N1 avian influenza to an additional farm. Japan is also experiencing an outbreak in poultry caused by the H5N1 virus. Other anecdotal and as yet unconfirmed reports have come from Indonesia, Thailand, Taiwan and Cambodia.
What is WHO doing?
In response to these developments, WHO has initiated a series of activities. These include support to national authorities in investigating the outbreaks and enhanced surveillance activities in Asia. WHO has also initiated the development of candidates and reagents for vaccine production, and antigenic and genetic assessments of the H5N1 strain to provide up-to-date diagnostic tests to national influenza centres. The WHO Global Influenza Network will receive virus and clinical specimens shortly. As a precautionary measure, network laboratories will immediately begin work on the development of a strain that can be used to produce a vaccine.