News update for avian flu

Archive Number 20060509.1338
Published Date 09-MAY-2006
Subject PRO/AH> Avian influenza, human - worldwide (61): GI trans.

AVIAN INFLUENZA, HUMAN - WORLDWIDE (61): GASTROINTESTINAL TRANSMISSION
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A ProMED-mail post

ProMED-mail is a program of the
International Society for Infectious Diseases


Date: Tue 9 May 2006
From: Mary Marshall
Source: Blomberg.com, Tue 9 May 2006 [edited]



Avian influenza may be capable of invading people through the gut,
not just the respiratory system, and diarrhea is sometimes the first
symptom, said virologist Menno de Jong, whose team observed 18 cases
in Viet Nam.

Particles of the lethal H5N1 virus contained in the meat and blood of
infected poultry may have been ingested by some patients, possibly
causing their infection, said De Jong, who is head of the Virology
Department at the Oxford University Clinical Research Unit in Ho Chi
Minh City. "In a number of patients the only exposure risk has been
drinking raw duck blood," De Jong said in a phone interview
yesterday. "That could imply that the gastrointestinal tract is also
a route of transmission or a route of first infection, and there are
experiments in animals" that suggest this.

Scientists are studying H5N1 patients to improve their understanding
and treatment of the virus, which has the potential to mutate into a
pandemic form that may kill millions of people. If live virus
particles are carried outside the lungs and surrounding tissues to
other parts of the body, some antiviral treatments such as inhaled
zanamivir, marketed by GlaxoSmithKline Plc as Relenza, may not be
effective treatments, De Jong said.

The infection rate in humans is increasing after more than 30
countries across three continents reported initial outbreaks in birds
so far in 2006. H5N1 has killed at least 115 of the 207 people known
to have been infected since late 2003, according to the World Health
Organization. [A complete breakdown of the figures of
laboratory-confirmed human cases of avian influenza by country and
year since 2003 up to 8 May 2006 is available at
.
- Mod.CP]

This year, 39 fatalities have been reported, almost as many as the 41
deaths recorded in the whole of 2005. Viet Nam accounts for 93 cases
and 42 deaths [since 2003 - Mod.CP]. Nonetheless, the Southeast Asian
nation hasn't reported any new infections in [the last] 6 months. In
almost all human H5N1 cases, infection was caused by close contact
with sick or dead birds, such as children playing with them, or
adults butchering them or taking off the feathers, according to the
Geneva-based WHO. Proper cooking of meat and eggs kills the virus.

In uncomplicated cases of seasonal influenza, disease is limited to
infection in the nose, throat and lungs. In contrast, H5N1 was
observed to have caused encephalitis, or swelling of the brain, in
one patient in Viet Nam, De Jong said. Virus particles collected from
numerous sites could be cultured, including from the throat, rectum,
blood and cerebralspinal fluid, he said. De Jong said it is possible
H5N1 may be replicating in the gastrointestinal tract after the virus
was cultured from a rectal swab in a patient who had diarrhea. For
some patients, the gastrointestinal tract may have been the initial
site of infection, possibly after the consumption of raw chicken or
raw duck products, he said.

Some scientists said survival of flu particles in the gut would be
difficult because of enzymes and bile that break down fats in the
process of food digestion. Flu particles are enveloped by a layer of
lipids or fats. "It's difficult to understand how the virus could
survive passage through the stomach and intestines," said Lorena
Brown, an associate professor in the Department of Microbiology and
Immunology at the University of Melbourne. The acid environment of
the stomach would denature protein-based components of the virus, she
said.

The systemic nature of illness caused by H5N1 poses challenges for
treating infected patients because, if the virus is spreading through
the blood, so too must drugs that aim to combat the infection. Roche
Holding AG's Tamiflu and GlaxoSmithKline's Relenza have shown signs
of fighting H5N1. Some studies have shown the virus binds
preferentially to human cells in the lower respiratory tract, whereas
the highest concentration of orally inhaled Relenza is found in the
upper respiratory tract.

"With the current data and with the current case reports, we should
assume that you should seek systemic coverage with drugs," De Jong
said. "I think, for instance, that the current formulation of
zanamivir isn't going to be of any use in the current avian flu. If a
pandemic strain evolves, we have to reconsider it because we won't
know if the change in the virus will also have changed the illness."

GlaxoSmithKline, Europe's biggest drugmaker, is developing an
intravenous form of Relenza, Nancy Pekarek, a U.S. spokeswoman for
the London-based company, said yesterday. Scientists are still
formulating the compound, and testing in people hasn't started, she
said.

--
Mary Marshall


[While it is reasonable to suggest that human infection has been
associated with a gastrointestinal route of infection in Viet Nam
because of the practice of consuming raw duck blood, it is a less
satisfactory explanation for the variable mortalities recorded
elsewhere. As of 8 May 2006, the percentage mortalities observed in
all 8 countries recording human cases of avian influenza is as
follows: Azerbaijan 63 percent (8 cases and 5 deaths); Cambodia 100
percent (6 / 6); China 67 percent (18 / 12); Egypt 39 percent (13 /
5); Indonesia 76 percent (33 / 25); Iraq 100 percent (2 / 2);
Thailand 64 percent (22 / 14); Turkey 33 percent (12 / 4); and Viet
Nam 45 percent (93 / 42 deaths); giving an overall mortality of 56
percent (207 cases, 115 deaths). - Mod.CP]