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[Influenza remains an unpredictable infection]
Abstract:
Influenza virus A (H5N1) was isolated from the tracheal swab of a 3-year-old boy who died from influenza with the Raye syndrome in Hong Kong in May, 1997. Up to the present time, influenza viruses with hemagglutinin H5 were known to circulate only among birds. They caused a variety of diseases: from asymptomatic to epizootic with 100% mortality, particularly among chickens. The main difference between virulent and avirulent strains is as follows: virulent viruses are isolated from all tissues of an infected bird. A (H5) virus hemagglutinin, transformed into a virulent variant, becomes sensitive to cleavage by proteases of mammalian and avian cells. Intensive epidemiological surveillance of influenza in Hong Kong started by the WHO and Department of Public Health of Hong Kong in August-September, 1997, resulted in detection of 17 more cases with Influenza A (H5N1) in November-December 1997. all of the occurred before December 28, 1997 and were detected in hospitals and health centers of Hong Kong. Nine patients were children aged under 5 years. Six patients died as a result of complications (pneumonia) and exacerbations of concomitant chronic diseases. Virological and logical studies showed that the main route of infection transmission was from birds to humans. Human to human transmission is probable. Study of 7 influenza A (H5N1) viruses isolated from patients showed that they contained all 8 RNA gene segments of avian virus. There are no reports about new cases of influenza A (H5N1) in humans in January 1998, and we can hope that the outbreak of Influenza A (H5N1) in Hong Kong caused by avian virus will not develop into a new influenza pandemic, although an unfavorable course of events is probable.
Insights
Avian Influenza A (H5N1) virus caused a deadly outbreak in Hong Kong in 1997, primarily spreading from birds to humans. While human-to-human transmission is possible, the outbreak did not escalate into a pandemic.
Area of Science:
- Virology
- Epidemiology
- Public Health
Context:
- Influenza A (H5N1) virus, previously known only in birds, emerged in humans in Hong Kong in 1997.
- The outbreak followed intensive surveillance by the WHO and local health authorities.
Purpose:
- To report the first isolation of Influenza A (H5N1) from a human case.
- To describe the epidemiology and virological characteristics of the 1997 Hong Kong outbreak.
- To assess the pandemic potential of avian Influenza A (H5N1) in humans.
Summary:
- Influenza A (H5N1) was isolated from a fatal case in a child, followed by 17 additional human cases, predominantly linked to avian sources.
- Virological studies confirmed the avian origin of the viruses, possessing all 8 RNA gene segments of avian strains.
- Most human cases involved children, with fatalities often due to complications like pneumonia.
Impact:
- The study highlighted the zoonotic potential of avian influenza viruses and the risk of human infection.
- It underscored the importance of epidemiological surveillance for early detection and response to novel influenza strains.
- The findings contributed to understanding the transmission dynamics and pathogenicity of Influenza A (H5N1) in humans, informing pandemic preparedness.