WHO reports on global trends in bird flu infections
The World Health Organisation has released a report analysing the
epidemiology all 205 confirmed cases of human bird flu infections.
The report, although based on somewhat inconsistent global data, draws
several conclusions about avian
- The number of new countries reporting human cases
increased from 4 to 9 after October 2005, following the geographical extension
of outbreaks among avian populations.
- Half of the cases occurred in
people under the age of 20 years; 90% of cases occurred in people under the age
of 40 years.
- The overall case-fatality rate was 56%. Case fatality
was high in all age groups but was highest in persons aged 10 to 39
- The case-fatality profile by age group differs from that seen
in seasonal influenza, where mortality is highest in the elderly.
overall case-fatality rate was highest in 2004 (73%), followed by 63% to date in
2006, and 43% in 2005.
- Assessment of mortality rates and the time
intervals between symptom onset and hospitalization and between symptom onset
and death suggests that the illness pattern has not changed substantially during
the three years.
- Cases have occurred all year round. However, the
incidence of human cases peaked, in each of the three years in which cases have
occurred, during the period roughly corresponding to winter and spring in the
northern hemisphere. If this pattern continues, an upsurge in cases could be
anticipated starting in late 2006 or early 2007.
information, view the full
Epidemiology of WHO-confirmed human cases of avian A(H5N1) infection report.
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