Influenza Update: ARDS Cluster in New Hampshire

|February 19, 2014

New Hampshire (NH) has reported widespread influenza activity in recent weeks. Of positive flu specimens, 94.2% are influenza A H1N1, followed by 3.2% influenza B and 2.6% influenza A H3. Further, one local hospital reported several patients diagnosed with acute respiratory distress syndrome (ARDS), with six of those cases attributed to H1N1. Four patients confirmed with influenza died. This situation warrants continued clinician awareness and prompt reporting of any severe illness that may occur as a result of influenza infection.

The NH Division of Public Health Services (DPHS) recommends:

  1. Review of the national trends for the influenza season to date.

  2. Awareness of locally reported severe illness associated with influenza.

  3. Continued monitoring of influenza activity and prompt reporting of any clusters, outbreaks, or cases of severe respiratory illness to NH Department of Health and Human Services (DHHS), DPHS, Bureau of Infectious Disease Control at 1-603-271-4496 (after hours, 1-800-852-3345, ext. 5300).

National Influenza Season Update

The predominant virus so far this season is H1N1. This virus has continued to circulate since the pandemic as a seasonal flu virus, but this is the first flu season since the pandemic that this virus has circulated so widely.

This season, a pattern of hospitalization that is similar to what was seen during the 2009 H1N1 pandemic has started to emerge. During the pandemic, younger people had more flu-related hospitalizations for severe illness than did older adults. If H1N1 virus continues to circulate widely, illness that disproportionately affects young and middle-aged adults may continue to occur this season.

The CDC has received several reports of severe flu illness among young and middle-aged adults, many of whom were infected with the 2009 H1N1 virus. Some hospitalizations and deaths have been reported.

To date this season, 61% of the reported hospitalizations have been in people 18 to 64 years old, while 24% of hospitalizations have occurred in adults 65 years and older. Usually 50% to 60% of flu hospitalizations occur in people aged 65 years and older.

Unfortunately, younger adults, especially those who are otherwise healthy, are less likely to get vaccinated. Estimates as of early November 2013 were that among people 18-49 years of age, only 31% had been vaccinated.

This season's pattern of more hospitalizations across younger age groups is likely due to higher existing levels of immunity to this virus in the older population.

Measures that reflect severity (like hospitalizations and deaths) are showing early signs of slowing, but it's possible these may increase again. (Severity indicators typically lag behind illness activity and hospitalization rates are cumulative over the season.)

During the week ending February 8, 2014, influenza activity decreased, but remained high overall in the United States, with 24 states reporting widespread activity.

For NH weekly influenza activity reports see

For any questions, please contact NH DHHS, DPHS, Bureau of Infectious Disease Control at 1-603-271-4496 (after hours, 1-800-852-3345, ext. 5300).

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