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Human infection by avian influenza A H5N1
KY Yuen, SSY Wong
Department of Microbiology, University of Hong Kong, Queen Mary
Hospital, Pokfulam Road, Hong Kong
The Southeast Asian outbreak of the highly lethal avian influenza
A H5N1 infection in humans is unlikely to abate because of the enormous
number of backyard farms providing poultry as the main source of food
protein in developing countries. This increases the risk of the emergence
of a reassortant pandemic influenza virus with improved human-to-human
transmissibility. Currently triage of suspected cases by epidemiological
risk factors remains the only practical way of case identification
for laboratory investigation and infection control. The clinical usefulness
of rapid diagnostic laboratory tests requires more vigorous evaluation.
The lethality of this disease may reflect systemic viral dissemination,
cytokine storm, or alveolar flooding due to inhibition of cellular
sodium channels. The present circulating genotype Z is intrinsically
resistant to amantadine and rimantadine. Prognosis may be improved
by early treatment with a neuraminidase inhibitor with good systemic
drug levels, and post-exposure prophylaxis for health care workers
is recommended. The role of immunomodulators and other modalities
of therapy requires evaluation in randomised controlled trials, with
prospective monitoring of the viral load and cytokine profiles in
various clinical specimens. In view of the high fatality of the disease,
a combination of contact, droplet, and airborne precautions are recommended
as long as resources allow despite the fact that the relative importance
of these three modes in nosocomial transmission of avian influenza
is still unknown.
Hong Kong Med J 2005;11:189-99
Key words: Hemagglutinins; Humans; Influenza A virus,
avian; Influenza A virus, human
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