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Visits to doctors for flu-like illnesses in the US declined again during the last reporting period (week 13) and continues well below what might be normally expected this time of year, according to this week’s FluView report.
With the exception of a few states in the Southeast, hospitalizations for H1N1 appear to be stable or on the decline. The P&I mortality rate has dropped from the previous week, and is now below the seasonal baseline.
A few excerpts then from this week’s CDC FluView report, followed by some data from the World Health Organization on the international situation.
2009-2010 Influenza Season Week 13 ending April 3, 2010
All data are preliminary and may change as more reports are received.
Synopsis:
During week 13 (March 28-April 3, 2010), influenza activity decreased slightly in the U.S.
- 105 (3.7%) 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.
- 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 below the epidemic threshold.
- One pediatric death associated with laboratory confirmed influenza A was reported; the subtype was undetermined.
- The proportion of outpatient visits for influenza-like illness (ILI) was 1.1%, 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. Three states reported regional influenza activity. Puerto Rico and three states reported local influenza activity. The District of Columbia, Guam and 33 states reported sporadic influenza activity. Eleven states reported no influenza activity, and the U.S. Virgin Islands 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 13, 7.2% 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 13.
Influenza-Associated Pediatric Mortality
One influenza-associated pediatric death was reported to CDC during week 13 (Florida) and was associated with an influenza A virus for which the subtype was undetermined. This death occurred during week 8 (the week ending February 27, 2010).
From the CDC’s page on the global situation, we get a summation of the latest WHO data.
2009 H1N1 Flu: International Situation Update
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, 278 have been found to be resistant to oseltamivir – 64 of these isolates were detected in the United States. Approximately 1% of U.S. 2009 H1N1 viruses tested by CDC since September 30, 2009, have been resistant to oseltamivir.
- Influenza B remains the predominant influenza virus subtype in some Asian countries, accounting for 64.8% of all influenza detections in China, 65.1% in the Russian Federation, 93.2% in the Republic of Korea, and 100% in Mongolia. Increased influenza B activity also continues to be observed in some European countries.
- In Chile, there is evidence of early 2009 H1N1 flu activity in advance of the usual start of the Southern Hemisphere winter flu season. New detections of 2009 H1N1 virus have been reported in at least three regions over the past two weeks, including small numbers of severe cases.
- On February 18, 2010, WHO published recommendations for the following viruses to be used for influenza vaccines in the 2010-2011 influenza season of the Northern Hemisphere:
- an A/California/7/2009 (H1N1)-like virus;
- an A/Perth/16/2009 (H3N2)-like virus*;
- a B/Brisbane/60/2008-like virus.
* A/Wisconsin/15/2009 is an A/Perth/16/2009 (H3N2)-like virus and is a 2010 Southern Hemisphere vaccine virus.
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