Jan 23, 2004 -- This may be the last flu story we carry for a while. For the first time since the reporting week ending November 8, the national percentage for influenza-like illness declined below the national baseline of 2.5%. And the number of states reporting widespread influenza activity continued to drop during the reporting week of January 11-17. Hopefully, this means that this year's flu season is coming to an end.
Of the flu viruses collected and characterized since October 2003, most were influenza A (H3N2). Of these, 18.8% were similar antigenically to the vaccine strain A/Panama but a whopping 81.2% were similar to a antigenic drift variant, A/Fujian. This drift variant was not included in this year's flu vaccine.
There will be a great deal of attention paid to what flu strains are included in next year's flu vaccine. And how much of it will be produced. We doubt anyone wants to see another flu vaccine shortage, as occurred this past season.
Barbara K. Hecht,
Frederick Hecht, M.D.
Medical Editors, MedicineNet.com
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Update: Influenza Activity --- United States, January 11--17, 2004
The number of states reporting widespread influenza activity* continued to decrease during the reporting week of January 11--17, 2004†. Health departments in five states reported widespread influenza activity. A total of 31 states and New York City reported regional activity, eight states reported local activity, and sporadic activity was reported by six states, the District of Columbia, Guam, and Puerto Rico (Figure 1). The percentage of outpatient visits for influenza-like illness (ILI)§ continued to decrease in all surveillance regions during the week ending January 17. For the first time since the reporting week ending November 8, 2003, the national percentage for ILI (2.0%) declined below the national baseline of 2.5%. The percentage of specimens testing positive for influenza also decreased, but the percentage of deaths attributed to pneumonia and influenza (P&I) was unchanged.
During the week ending January 17, World Health Organization (WHO) laboratories reported testing 1,544 specimens for influenza viruses, of which 123 (8.0%) were positive. Of these, 26 were influenza A (H3N2) viruses, 95 were influenza A viruses that were not subtyped, and two were influenza B viruses.
Since September 28, WHO and NREVSS laboratories have tested 76,311 specimens for influenza viruses, of which 19,968 (26.2%) were positive. Of these, 19,853 (99.4%) were influenza A viruses, and 115 (0.6%) were influenza B viruses. Of the 19,853 influenza A viruses, 4,652 (23.4%) have been subtyped; 4,651 (99.9%) were influenza A (H3N2) viruses, and one (0.1%) was an influenza A (H1) virus.
Of the 573 influenza viruses collected by U.S. laboratories since October 1, 2003, and characterized antigenically by CDC, 565 were influenza A (H3N2) viruses, two were influenza A (H1) viruses, and six were influenza B viruses. The hemagglutinin proteins of the influenza A (H1) viruses were similar antigenically to the hemagglutinin of the vaccine strain A/New Caledonia/20/99. Of the 565 influenza A (H3N2) isolates that have been characterized, 106 (18.8%) were similar antigenically to the vaccine strain A/Panama/2007/99 (H3N2), and 459 (81.2%) were similar to a drift variant, A/Fujian/411/2002 (H3N2)**. Five influenza B viruses characterized were similar antigenically to B/Sichuan/379/99 and one was similar antigenically to B/Hong Kong/330/2001.
P&I Mortality Surveillance
During the week ending January 17, P&I accounted for 10.3% of all deaths reported through the 122 Cities Mortality Reporting System. This percentage is again above the epidemic threshold†† of 8.1% (Figure 2).
The percentage of patient visits§§ to approximately 1,000 U.S. sentinel providers nationwide for ILI decreased to 2.0% for the week ending January 17, which is below the national baseline of 2.5% (Figure 3). The percentage of patient visits for ILI continued to decrease in all nine surveillance regions, ranging from 2.5% in the Pacific region to 1.1% in the New England and West North Central regions.
Activity Reported by State and Territorial Epidemiologists
During the week ending January 17, influenza activity was reported as widespread in five states (Delaware, Minnesota, New York, Pennsylvania, and Vermont). Regional activity was reported in 31 states (Colorado, Connecticut, Florida, Georgia, Hawaii, Idaho, Indiana, Iowa, Kentucky, Louisiana, Maine, Massachusetts, Michigan, Mississippi, Missouri, Montana, New Hampshire, New Jersey, North Carolina, North Dakota, Ohio, Oregon, Rhode Island, South Carolina, Tennessee, Texas, Utah, Virginia, West Virginia, Wisconsin, and Wyoming) and New York City. Local activity was reported in eight states (Alaska, Arizona, California, Illinois, Kansas, Maryland, Nebraska, and Washington). Sporadic activity was reported in six states (Alabama, Arkansas, Nevada, New Mexico, Oklahoma, and South Dakota), the District of Columbia, Guam, and Puerto Rico.
Influenza-Associated Deaths in Children Aged <18 Years
As of January 20, 2004, CDC had received reports of 111 influenza-associated deaths in U.S. residents aged <18 years. This update is based on preliminary data reported from 33 states (Table). All patients had evidence of influenza virus infection detected by rapid-antigen testing or other laboratory tests. Among reported deaths, 56 (50.5%) were male. The median age was 4 years (range: 1 month--17 years). Of the 64 children aged <5 years, 38 were aged 6 months--23 months. Twenty-one children had high-risk medical conditions that put them at increased risk for complications from influenza. Of the children whose influenza vaccination status was reported, three were vaccinated according to recommendations (1), and 49 were not vaccinated.
Source: CDC MMWR Weekly, January 23, 2004 (www.cdc.gov)