• Vol. 36 No. 4, 285–292
  • 15 April 2007

Review of Human Infections with Avian Influenza H5N1 and Proposed Local Clinical Management Guideline



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Introduction: The current avian and human H5N1 influenza epidemic has been in resurgence since 2004. We decided to evaluate published evidence in relation to epidemiology, clinical features and course, laboratory diagnosis, treatment and outcome of human H5N1 influenza, and develop institutional clinical management guidelines. Methods: A search of PubMed was conducted for all English language articles with search terms “avian”, “influenza” and “H5N1”. The bibliography of articles was searched for other references of interest. Results: Published case series from Hong Kong in 1997, and Thailand and Vietnam since 2004 have indicated a rapidly progressive primary viral pneumonia resulting in acute respiratory distress syndrome. The majority of human H5N1 infections can be linked to poultry exposure. Hitherto there has been no evidence of efficient human-to-human transmission. Case fatality rates have varied from 71% in Thailand to 100% in Cambodia. Oseltamivir appears to be the only potentially effective antiviral therapy. H5N1 isolates in Vietnam have become resistant to oseltamivir, resulting in persistent viral replication and death. There is as yet no effective human H5N1 vaccine. Conclusions: National and international preparedness plans are well advised. Clinical trials to evaluate higher dose oseltamivir therapy and immunomodulatory treatment are urgently needed.

The current human H5N1 outbreak occurred in Hong Kong for the first time in 1997, with another 2 human cases in the same city in February 2003. Since December 2003, when the resurgent outbreak of avian influenza H5N1 occurred in poultry in Seoul, Korea, it has spread to 12 Asian countries (Japan, China, Laos, Cambodia, Thailand, Vietnam, Malaysia, Indonesia, Taiwan, Hong Kong, Mongolia and India) and 15 countries in western and eastern Europe (France, Germany, Greece, Italy, Romania, Austria, Bulgaria, Russia, Bosnia, Croatia, Slovenia, Azerbaijan, Ukraine, Kazakhstan and Turkey) as of 27 February 2006. In addition, avian H5N1 has also been reported in Africa (Egypt and Nigeria) and the Middle East (Iraq and Iran).1 The first avian-to-human transmission was reported in Vietnam and Thailand in January 2004,2 and as of 27 February 2006, 7 countries have confirmed human H5N1 infections (Cambodia, China, Indonesia, Iraq, Thailand, Turkey and Vietnam).3 The current number of human H5N1 infections totalled 170 cases, with 92 deaths.3 This has led to frenetic media attention and unprecedented international and national alertness, and preparation for a potential influenza pandemic in the event of increasingly efficient human-to-human transmission.

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