18 February 2004
WHO Urges Continued Vigilance Against Bird Flu in Asia
Eight-nation outbreak called "historically unprecedented"
The World Health Organization (WHO) is calling on Asian nations
experiencing widespread bird flu outbreaks to remain persistent
in their intensive efforts to contain the virus. An epidemic update
issued from WHO's Geneva headquarters February 18 said the avian
influenza is not yet under control despite the destruction of an
estimated 80 million birds.
WHO also reported that the flu's toll on humans is growing more
serious. Both Thailand and Vietnam are reporting additional deaths
of people infected with the dangerous H5N1 virus that is infecting
birds. A total of 31 human cases have been confirmed, resulting
in 22 deaths. Thailand and Vietnam are the only nations to report
human cases, and that fact seems to indicate that while the H5N1
flu strain is capable of crossing from birds to humans, it does
not do so easily.
The human cases apparently result from direct contact between
birds and humans, which means that the virus doesn't appear to
have mutated into a form that would be transmitted from person-to-person.
That possibility -- and the resulting consequence of a rapidly
spreading, worldwide flu epidemic -- is why international public
health experts are maintaining such a close watch on the progression
of this disease outbreak.
"The present situation in Asia is historically unprecedented and
extremely challenging, " according to the WHO update. "Many affected
countries are reporting highly pathogenic H5N1 infection in birds
for the first time in their histories."
The latest information on the Asia bird flu situation is available
Following is the text of WHO's latest avian influenza update:
WORLD HEALTH ORGANIZATION
Avian influenza A(H5N1)
February 18, 2004
Situation (human) in Thailand
The Ministry of Public Health in Thailand has today confirmed
an additional case of H5N1 infection. The case, which was fatal,
was a four-year-old boy from Khon Kaen Province. He died on 3 February.
To date, Thailand has reported nine cases of human H5N1 infection.
Of these, seven were fatal.
Situation (human) in Viet Nam
The Ministry of Health in Viet Nam has today confirmed an additional
case of H5N1 infection. Further details about the case, which was
fatal, are pending. To date, Viet Nam has reported 22 cases of
human H5N1 infection. Of these, 15 were fatal.
Situation (poultry) in Asia
Highly pathogenic avian influenza, caused by the H5N1 strain,
is currently infecting poultry in 8 Asian countries. Full control
has not yet been achieved in any of these countries, despite intensive
efforts in many.
Past experience with outbreaks of highly pathogenic avian influenza,
previously considered rare, has demonstrated the difficulty of
fully eliminating the virus in bird populations. Control has often
taken several years, even under favourable circumstances (small
geographical area, concentration in commercial production facilities).
In past outbreaks, investigations have shown that infection can
be introduced into domestic flocks by wild aquatic birds, including
migratory birds capable of flying long distances. The virus multiplies
in the intestines of these birds, which can carry the virus without
developing signs of infection, and very large quantities of virus
are shed in faeces.
Once introduced into domestic flocks, the virus, which is highly
contagious, can be mechanically carried from farm to farm via contaminated
items, such as vehicles, clothing, and equipment.
Water sources contaminated by droppings from wild birds and shared
by domestic poultry are just one example of how chains of transmission
can be sustained once the virus becomes widespread in the environment.
In the present outbreaks, the tendency to hide or smuggle especially
valuable birds, such as fighting cocks, can also help maintain
the virus in the environment or contribute to its further geographical
The present situation in Asia is historically unprecedented and
extremely challenging. Many affected countries are reporting highly
pathogenic H5N1 infection in birds for the first time in their
histories. In some of these countries, around 80% of the poultry
are produced in small backyard farms scattered throughout rural
areas, further complicating control.
Complete elimination of the virus is becoming increasingly challenging.
As explained below, the consequences for human health could be
China- Outbreaks of H5N1 infection in poultry, first reported
on 27 January, have continued to spread. To date, authorities have
reported 52 outbreaks at poultry farms, of which 43 have been confirmed
as caused by H5N1. Altogether, 16 of the country's 31 provinces,
autonomous regions, and municipalities have been affected. Xizang
(Tibet) Autonomous Region and Jilin Province are the most recently
As formally reported to OIE on 11 February, around 2.3 million
poultry have been culled.
Japan- Authorities have confirmed a small outbreak in Oita Prefecture
as caused by the H5 subtype. Further testing is under way to confirm
the possible involvement of the H5N1 strain.
Republic of Korea- On 7 February, authorities reported new outbreaks
at 8 duck farms, 7 chicken farms, and one mixed farm with chickens
and ducks. Around 350,000 birds died or were destroyed in the most
Thailand- Authorities in Thailand have today reported 14 new outbreaks
in various provinces, including one province where the disease
had not been reported previously. More than 27 million birds have
either died or been destroyed. Infections in chickens, ducks, geese,
turkeys, ostriches, quail, and peacocks have been reported.
Viet Nam- Outbreaks have been detected in 57 of the country's
64 provinces affected. More than 27 million birds have either died
or been destroyed. Cambodia, Indonesia, Laos- Information on the
status of poultry outbreaks in these countries is still being gathered.
Implications for human health
The H5N1 strain has demonstrated its capacity to directly infect
humans on three occasions in the recent past. The H5N1 strain is
capable of infecting a broad range of hosts, which may help explain
recent media reports of infections and deaths in mammalian and
avian species not normally considered susceptible to infection
and severe disease.
In humans, the disease caused by H5N1 infection differs from that
usually caused by influenza viruses, where respiratory symptoms
are dominant. H5N1 has a documented ability to replicate in a wide
range of cell types, resulting in severe disseminated disease affecting
multiple organs and causing high mortality. These clinical features
were observed during the first recorded human outbreak of H5N1
infection in Hong Kong in 1997. These features are being seen again
in the earliest clinical reports from Viet Nam and Thailand.
For all these reasons, the present situation in Asia needs to
be watched very carefully. Countries need to maintain a high level
of vigilance, and must not relax their surveillance and detection
efforts. Intense efforts to control the disease in poultry must
continue in some countries and be initiated in others.
Preparedness measures for dealing with an incipient pandemic situation,
launched by WHO last month, are continuing and much progress is