# 4503
The spread and evolution of influenza around the globe remains a poorly understood phenomenon, often leaving scientists scratching their heads in puzzlement. Few scientists would have predicted last October the relative quiescence we have seen in the novel H1N1 virus over the past three months.
The much anticipated `third wave’ may yet arrive, of course. Pandemic strains are rarely respecters of traditional flu seasons, a point driven home by the emergence of this novel virus over the summer of 2009.
And there is always the likely resurgence of H1N1 next fall and winter to consider.
For now, however, the big player on the global scene (excluding North America) is influenza B.
In China, nearly 90% of all positive influenza samples are coming back as a `B’ strain, not pandemic H1N1. In Korea, that number exceeds 95% (WHO Update #96).
High percentages of Influenza B are reported in other parts of Asia, the Russian Federation, and Europe. In the United States, influenza B remains a marginal player, comprising less than 1% of flu-positive samples last week.
Selected Highlights
According to WHO, the majority of 2009 H1N1 virus isolates tested worldwide remain sensitive to oseltamivir, an antiviral medicine used to treat flu. Among 2009 H1N1 isolates tested worldwide, 285 have been found to be resistant to oseltamivir – 64 of these isolates were detected in the United States. Approximately 1.2% of U.S. 2009 H1N1 viruses tested by CDC since September 30, 2009, have been resistant to oseltamivir. Influenza B was reported as the predominate influenza virus accounting for 68.6% of all influenza detections in the Russian Federation, 72.7% in Cameroon, 88.7% in China, 95.2% in the Republic of Korea, and 100% in Mongolia. An increase in influenza B activity has also been observed in other countries including Italy, Kazakhstan, Latvia, Singapore and Sweden. Sporadic influenza A (H3N2) activity was also reported from certain countries in East Asia and Europe, including China, Japan, the Russian Federation, Singapore and Thailand.
A few choice excerpts from this week’s FluView report from the CDC. Follow the link to read it in its entirety.
2009-2010 Influenza Season Week 14 ending April 10, 2010
All data are preliminary and may change as more reports are received.
Synopsis:
During week 14 (April 4-10, 2010), influenza activity decreased in the U.S.
- 52 (2.7%) 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.
- Among 34 subtyped influenza A viruses, 33 were 2009 influenza A (H1N1) and one was influenza A (H3).
- The proportion of deaths attributed to pneumonia and influenza (P&I) was below the epidemic threshold.
- Three influenza-associated pediatric deaths were reported. One was associated with 2009 influenza A (H1N1) virus infection, one was associated with an influenza A virus for which the subtype was undetermined, and one death was associated with a seasonal influenza A (H1) virus infection, but occurred during the 2008-09 season.
- The proportion of outpatient visits for influenza-like illness (ILI) was 0.9%, which is below the national baseline of 2.3%. All 10 regions reported ILI below region-specific baseline levels.
- No states reported widespread influenza activity. Two states reported regional influenza activity. Puerto Rico and one state reported local influenza activity. The District of Columbia, Guam and 37 states reported sporadic influenza activity. The U.S. Virgin Islands and nine states reported no influenza activity, and one state did not report.
U.S. Virologic Surveillance:
WHO and NREVSS collaborating laboratories located in all 50 states and Washington, D.C. report to CDC the number of respiratory specimens tested for influenza and the number positive by influenza type and subtype. The results of tests performed during the current week are summarized in the table below.
Pneumonia and Influenza (P&I) Mortality Surveillance
During week 14, 7.0% of all deaths reported through the 122-Cities Mortality Reporting System were due to P&I. This percentage was below the epidemic threshold of 7.7% for week 14.
Influenza-Associated Pediatric Mortality
Three influenza-associated pediatric deaths were reported to CDC during week 14 (New York City and Texas [2]). One death was associated with a seasonal influenza A (H1) virus infection, one was associated with 2009 influenza A (H1N1) virus infection, and one was associated with an influenza A virus for which the subtype was undetermined. The deaths reported during week 14 occurred between May 3, 2009, and March 27, 2010. The death associated with seasonal influenza A (H1) reported during week 14 occurred during the 2008-09 season, bringing the total number of reported pediatric deaths occurring during that season to 134.
