H1N1 Flu: Situation Update, April 23, 2010

Atlanta, GA–(ENEWSPF)–April 23, 2010.

Each week CDC analyzes information about influenza disease activity in the United States and publishes findings of key flu indicators in a report called FluView. During the week of April 11-17, 2010, nationally most key flu indicators declined slightly from the previous week. Overall, influenza activity is low in the United States. Below is a summary of the most recent key indicators:

  • Visits to doctors for influenza-like illness (ILI) declined from last week and are low nationally, with all 10 U.S. regions reporting ILI below region-specific baseline levels.
  • Laboratory-confirmed hospitalizations rates have leveled off and very few hospitalizations were reported by states during the week ending April 17.
  • The proportion of deaths attributed to pneumonia and influenza (P&I) based on the 122 Cities Report increased over last week, but in general, are not higher than expected. Also, this indicator can lag behind the others. No pediatric deaths were reported this week. Since April 2009, CDC has received reports of 337 laboratory-confirmed pediatric deaths: 281 due to 2009 H1N1, 53 pediatric deaths that were laboratory confirmed as influenza A, but the flu virus subtype was not determined, and three pediatric deaths that were associated with seasonal influenza viruses. (Laboratory-confirmed deaths are thought to represent an undercount of the actual number. CDC has provided estimates about the number of 2009 H1N1 cases and related hospitalizations and deaths).
  • No states reported widespread or regional influenza activity. This is the first week since the week ending December 13, 2008 that no states are reporting widespread or regional flu activity.
  • The majority of the influenza viruses identified so far continue to be 2009 H1N1 influenza A viruses. These viruses remain similar to the virus chosen for the 2009 H1N1 vaccine and remain susceptible to the antiviral drugs oseltamivir and zanamivir with rare exception.

*All data are preliminary and may change as more reports are received.

Laboratory Confirmed Influenza-Associated Hospitalizations
and Deaths from August 30 2009 to April 3, 2010

As of April 16, 2010, the Aggregate Hospitalizations and Deaths Reporting Activity (AHDRA) has concluded for the 2009-2010 flu season. The AHDRA surveillance system was created specifically in response to the 2009 H1N1 pandemic, and the system will be maintained for quick implementation in the event of another flu pandemic. CDC will continue to track hospitalizations and deaths through its traditional seasonal flu surveillance systems during the 2010-2011 season. Pneumonia and influenza-related deaths in adults and children will be tracked through the 122 Cities Mortality Reporting System. Laboratory confirmed, flu-related deaths in children will continue to be tracked through the Influenza-associated Pediatric Mortality Surveillance system. Laboratory confirmed, flu-related hospitalizations in adults and children will be tracked through the Emerging Infections Program (EIP).

Cases Defined by
Hospitalizations
Deaths
Influenza Laboratory-Tests** 41,821 2,117

*Reports can be based on syndromic, admission or discharge data, or a combination of data elements that could include laboratory-confirmed and influenza-like illness hospitalizations.

*Laboratory confirmation includes any positive influenza test (rapid influenza tests, RT-PCR, DFA, IFA, or culture), whether or not typing was done.

The table shows aggregate reports of all laboratory confirmed influenza hospitalizations and deaths (including 2009 H1N1 and seasonal flu) since August 30, 2009 received by CDC from U.S. states and territories**. This table will be updated weekly each Friday at 11 a.m. For the 2009-2010 influenza season, states are reporting based on new case definitions for hospitalizations and deaths effective August 30, 2009.

CDC will continue to use its traditional surveillance systems to track the progress of the 2009-2010 influenza season. For more information about influenza surveillance, including reporting of influenza-associated hospitalizations and deaths, see Questions and Answers: Monitoring Influenza Activity, Including 2009 H1N1.

The number of 2009 H1N1 hospitalizations and deaths reported to CDC from April – August 2009 is available on the Past Situation Updates page.

For state level information, refer to state health departments.

International Human Cases of 2009 H1N1 Flu Infection
See: World Health Organization.

**States report weekly to CDC either 1) laboratory-confirmed influenza hospitalizations and deaths or 2) pneumonia and influenza syndrome-based cases of hospitalization and death resulting from all types or subtypes of influenza. Although only the laboratory confirmed cases are included in this report, CDC continues to analyze data both from laboratory confirmed and syndromic hospitalizations and deaths.

 

U.S. Influenza-associated Pediatric Mortality
Posted April 23, 2010 (Updated Weekly)
Data reported to CDC by April 17, 2010
Date Reported
Laboratory-Confirmed 2009 H1N1 Influenza Pediatric Deaths
Laboratory-Confirmed Influenza A Subtype Unknown Pediatric Deaths
Laboratory-Confirmed
Seasonal
Influenza
Total
This Week (Week 15, April 11- April 17, 2010) 0 0 0 0
Since August 30, 2009 221 50 1 272
Cumulative since April 26, 2009 281 53 3 337

This table is based on data reported to CDC through the Influenza-Associated Pediatric Mortality Surveillance System. Influenza-associated deaths in children (persons less than 18 years) was added as nationally notifiable condition in 2004.

For more information about influenza-associated pediatric mortality, see FluView.

Source: cdc.gov