Thursday, December 31, 2009

Pandemic (H1N1) 2009 - Update

30 December 2009 -- As of 27 December 2009, worldwide more than 208 countries and overseas territories or communities have reported laboratory confirmed cases of pandemic influenza H1N1 2009, including at least 12220 deaths.

The most active areas of pandemic influenza transmission currently are in central and eastern Europe.

In North America, influenza transmission remains widespread but has declined substantially in all countries. Rates of hospitalization among cases aged 5-17 years and 18-49 year far exceeded rates observed during recent influenza seasons, while rates of hospitalizations among cases aged >65 years were far lower than those observed during recent influenza seasons.


During week 51 (December 20-26, 2009), influenza activity decreased slightly in the U.S.

  • 154 (3.9%) specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories and reported to CDC/Influenza Division were positive for influenza.
  • All subtyped influenza A viruses reported to CDC were 2009 influenza A (H1N1) viruses.
  • The proportion of deaths attributed to pneumonia and influenza (P&I) was above the epidemic threshold.
  • Four influenza-associated pediatric deaths were reported. Two of these deaths were associated with 2009 influenza A (H1N1) virus infection and two were associated with an influenza A virus for which the subtype was undetermined.

Via Virology Blog -

Reinfection with 2009 influenza H1N1

In healthy individuals, the first encounter with a virus leads to a
primary antibody response. When an infection occurs with the same or a similar virus, a rapid antibody response occurs that is called the secondary antibody response. Antibodies are critical for preventing many viral infections, including influenza. But reinfection may occur if we encounter the same virus before the primary response is complete.

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