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Published Date: 2011-08-29 17:39:48
Subject: PRO/AH/EDR> Avian influenza, human (57): alert
Archive Number: 20110829.2654

AVIAN INFLUENZA, HUMAN (57): ALERT
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International Society for Infectious Diseases
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Date: Mon 29 Aug 2011
Source: Food and Agriculture Organisation of The United Nations (FAO)
News Centre [edited]
http://www.fao.org/news/story/en/item/87196/icode/

The FAO today [29 Aug 2011] urged heightened readiness and
surveillance against a possible major resurgence of the H5N1 highly
pathogenic avian influenza amid signs that a mutant strain of the
deadly bird flu virus is spreading in Asia and beyond, with
unpredictable risks to human health.

The H5N1 virus has infected 565 people since it 1st appeared in 2003,
killing 331 of them, according to WHO figures [summarised in:
http://www.who.int/csr/disease/avian_influenza/country/cases_table_2011_08_19/en/].
The latest death occurred earlier this month [August 2011] in
Cambodia, which has registered 8 cases of human infection this year
[2011] -- all of them fatal (see: ProMED-mail report archived as:
Avian influenza, human (56): Cambodia (KC) 20110819.2525).

Since 2003, H5N1 has killed or forced the culling of more than 400
million domestic poultry and caused an estimated USD 20 billion of
economic damage across the globe before it was eliminated from most of
the 63 countries infected at its peak in 2006.

However, the virus remained endemic in 6 nations, although the number
of outbreaks in domestic poultry and wild bird populations shrank
steadily from an annual peak of 4000 to just 302 in mid 2008. But
outbreaks have risen progressively since [then], with almost 800 cases
recorded in 2010-2011.

At the same time, 2008 marked the beginning of renewed geographic
expansion of the H5N1 virus both in poultry and wild birds. The
advance appears to be associated with migratory bird movements,
according to FAO chief veterinary officer Juan Lubroth. He said
migrations help the virus travel over long distances, so that H5N1
has, in the past 24 months, shown up in poultry or wild birds in
countries that had been virus-free for several years. "Wild birds may
introduce the virus, but peoples' actions in poultry production and
marketing spread it," Lubroth noted.

Recently affected areas are to be found in Israel and the Palestinian
Territories, Bulgaria, Romania, Nepal, and Mongolia.

A further cause for concern, Lubroth said, is the appearance in China
and Viet Nam of a variant virus apparently able to sidestep the
defenses provided by existing [veterinary] vaccines. In Viet Nam,
which suspended its springtime poultry vaccination campaign this year
[2011], most of the northern and central parts of the country -- where
H5N1 is endemic -- have been invaded by the new virus strain, known as
H5N1 - 2.3.2.1.

Viet Nam's veterinary services are on high alert and reportedly are
considering a novel, targeted vaccination campaign this fall [2011].
Virus circulation in Viet Nam poses a direct threat to Cambodia,
Thailand, and Malaysia as well as endangering the Korean peninsula and
Japan further afield. Wild bird migration can also spread the virus to
other continents.

"The general departure from the progressive decline observed in
2004-2008 could mean that there will be a flare up of H5N1 this fall
and winter [2011-12], with people unexpectedly finding the virus in
their backyard," Lubroth said. The countries where H5N1 is still
firmly entrenched -- Bangladesh, China, Egypt, India, Indonesia, and
Viet Nam -- are likely to face the biggest problems, but no country
can consider itself safe, he said. "Preparedness and surveillance
remain essential," Lubroth underlined. "This is no time for
complacency. No one can let their guard down with H5N1."

--
communicated by:
ProMED-mail rapporteur Mary Marshall

[According to WHO, the primary risk factor for human infection appears
to be direct or indirect exposure to infected live or dead poultry or
contaminated environments. Controlling circulation of the H5N1 virus
in poultry is essential to reducing the risk of human infection. Given
the persistence of the H5N1 virus in some poultry populations, control
will require long term commitments from countries and strong
coordination between animal and public health authorities.

There is no evidence to suggest that the H5N1 virus can be transmitted
to humans through properly prepared poultry or eggs. A few human cases
have been linked to consumption of dishes made of raw, contaminated
poultry blood. However, slaughter, defeathering, handling carcasses of
infected poultry, and preparing poultry for consumption, especially in
household settings, are likely to be risk factors.

Influenza pandemics (outbreaks that affect a large proportion of the
world) are unpredictable but recurring events that can have health,
economic, and social consequences worldwide. An influenza pandemic
occurs when key factors converge: an influenza virus emerges with the
ability to cause sustained transmission from human-to-human, and there
is very low, or no, immunity to the virus among most people. In the
interconnected world of today, a localized epidemic can transform into
a pandemic rapidly, with little time to prepare a public health
response to halt the spread of illness.

The H5N1 AI virus remains one of the influenza viruses with pandemic
potential, because it continues to circulate widely in some poultry
populations, most humans likely have no immunity to it, and it can
cause severe disease and death in humans. In addition to H5N1, other
animal influenza virus subtypes reported to have infected people
include avian H7 and H9, and swine H1 and H3 viruses. H2 viruses may
also pose a pandemic threat. Therefore, pandemic planning should
consider risks of emergence of a variety of influenza subtypes from a
variety of sources (see:
http://www.who.int/mediacentre/factsheets/avian_influenza/en/index.html).

Avian influenza A/(H5N1) virus has been continuously evolving as
indicated by the clade designation 2.3.2.1. FAO has been prudent to
draw attention to the resurgence of avian influenza in poultry and the
prevalence of a novel strain apparently not susceptible to control by
currently deployed veterinary vaccines. However, there is no evidence
as yet to indicate that this new strain is more transmissible to and
between humans. The high lethality of avian H5N1 influenza virus for
humans in Cambodia is not a new or general phenomenon. - Mod.CP]

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