Severe Influenza-Associated Critical Illness Prompts CDC Health Advisory

Influenza activity is increasing across the country and the U.S. Centers for Disease Control and Prevention (CDC) has received reports of severe influenza illness.

Since October 2015, the CDC has detected co-circulation of influenza A(H3N2), A(H1N1)pdm09, and influenza B viruses. However, H1N1pdm09 viruses have predominated in recent weeks. The CDC has issued a Health Advisory urging rapid antiviral treatment of very ill and high-risk suspect influenza patients without waiting for testing.

The CDC has received recent reports of severe respiratory illness among young- to middle-aged adults with H1N1pdm09 virus infection, some of whom required intensive care unit admission. Fatalities have been reported. Some of these patients reportedly tested negative for influenza by RIDT (rapid influenza diagnostic test); their influenza diagnosis was made later with molecular assays. Most of these patients were reportedly unvaccinated. H1N1pdm09 virus infection in the past has caused severe illness in some children and young- and middle-aged adults.

In response to this cluster of cases, mostly reported in Arizona, the U.S. Critical Illness and Injury Trials Group has published a comprehensive review of the salient epidemiologic, diagnostic and therapeutic features that have been learned from the experience with influenza A (H1N1)pdm09 virus infection in adults.

Clinicians should continue efforts to vaccinate patients this season for as long as influenza viruses are circulating, and they should promptly start antiviral treatment of severely ill and high-risk patients if influenza is suspected or confirmed.

Keep up to date on influenza with the CDC’s weekly surveillance reports:

Weekly Reports
Weekly Summary

Visit for additional influenza resources.

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