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Review Article: Avian Influenza Infection in Human
Rangsima Lolekha, M.D., Tawee Chotpitayasunondh, M.D., Somsak Lolekha, M.D.

ABSTRACT

Avian influenza (AI) viruses do not commonly infect human. Human infections with AI A
(H5N1, H9N2, H7N7 and H7N2) viruses have been reported in Hong Kong, the Netherlands, Vietnam,
Thailand, Canada and the US since 1997. The H7-type AI viruses are less virulent than the H5-type
strain, and usually associate with conjunctivitis and mild influenza-like illness in humans. The H5-type
strains usually associate with respiratory distress with high fatality. Tests for diagnosing all influenza
strains of animals and humans are rapid and reliable. Antiviral drugs used for treatment and prevention
are clinically effective against influenza A virus strains in healthy adults and children, but they are still
expensive and supplies are limited. Experience in the production of influenza vaccines is also considerable,
particularly as vaccine composition changes each year to match changes in circulating virus due to
antigenic drift. A least four months would be needed to produce a new vaccine capable of conferring
protection against a new virus subtype. At present, human-to-human transmission of AI virus was limited.
However, it is of particular concern because AI mutates rapidly and has a documented propensity to
acquire genes from viruses infecting other animal species. If the host is concurrently infected with human
and AI strains which can be served as the “mixing vessel” for the emergence of a novel subtype that can
infect human, this could lead to the start of an influenza pandemic. The world needs to be better prepared
to respond to the next influenza pandemic. Improved influenza surveillance, good public health network,
antiviral agents and vaccine development are important for preparedness of the next pandemic. (J Infect
Dis Antimicrob Agents 2004;21:99-110.)