2011-02-06-世界卫生组织-Influenza_at_the_human-animal_interface_summary_and_assessment,_7_March_2011_3页_225kb

Influenza H5N1 Human Infections Summary (February 2011 Events)

Overall Situation

According to WHO reports, there were 528 confirmed human cases of avian influenza H5N1 infection between 2003 and February 28, 2011, in 15 countries. Of these, 311 deaths occurred, with a case fatality rate of approximately 59%. Epidemiological investigations showed only limited human-to-human transmission, with no community-level spread since the virus emerged in 2003.

Key Events in February 2011

• Six human cases with onset dates in February 2011 were reported from two countries: Egypt (four cases, four deaths, case fatality rate 25%) and Cambodia (two cases). Notably, Egypt also reported two additional cases from January, and Indonesia reported one case from January that were not included in prior summaries.
• All cases involved contact with sick or dead poultry or visits to live poultry markets. The H5N1 virus circulates endemically in poultry in Egypt and Indonesia, while in Cambodia, it shows sporadic reintroduction.
• The epidemiological curve of human cases follows seasonal patterns, with higher incidence in winter months and decrease in summer, mirroring poultry outbreaks.

Country-Specific Details

• Egypt: Human cases are regularly reported, reflecting national surveillance systems. The recent increase aligns with seasonal expectations. Ongoing risks include exposure to infected poultry, and collaboration between animal health and public health sectors aims to reduce risks, though political instability may impact infrastructure.
• Cambodia: Since 2005, there have been 13 human cases with 11 deaths. In February 2011, a mother and son (both with onset on February 5) were likely infected through a common poultry source. Human cases show a temporal correlation with poultry outbreaks, exhibiting seasonal patterns.

Virus Characteristics and Future Outlook

• H5N1 subtype clade 2.3.2 is circulating in Asia and may be more adapted to wild birds, potentially leading to increased spread. Human cases are reported sporadically.
• Cases occur worldwide, but incidence decreases with warmer weather, while animal outbreaks may continue. Fewer human cases are associated with commercial poultry operations compared to village or household birds.
• No other animal influenza viruses caused human infections in February 2011.

Conclusions

The H5N1 virus remains a concern with ongoing surveillance, limited human-to-human transmission, and potential for sporadic cases based on poultry circulation. Continued monitoring and risk reduction efforts are essential.