CDC: Flu Activity on Decline, But Remains High Overall

Despite signs that influenza activity is declining, overall activity remains elevated across most of the United States following this season’s peak in early February, according to the CDC’s latest FluView report.

This year’s flu season continues to break recent records in terms of higher than average hospitalization rates. According to the report, the overall and all age-specific hospitalization rates surpassed end-of-season hospitalization rates for the 2014-2015 season, which was also an influenza-A predominant season categorized as high severity. Overall, cumulative hospitalization rates so far have reached 81.7 per 100,000 people in the United States, and have been the highest since 2010.

For percentage of visits for influenza-like illness (ILI), this year’s flu season reached its peak at 7.4% in early February and has decreased since then, although 45 states continue to report widespread illness activity. As of the week ending February 24, ILI dropped from 6.4% reported the week before to 5%. Current rates are now similar to the peak of last season.

Additionally, 17 flu-related pediatric deaths have been reported for week 8, bringing the total for this season up to 114.

Although recent vaccine effectiveness (VE) estimates have shown only 25% VE for the H3N2 viruses, VE is estimated to be 36% overall, 67% against H1N1, and 42% against B viruses. While H3N2 viruses remain predominant overall this season, the proportion of B viruses versus A viruses is now almost even. According to the report, B viruses have been increasing in recent weeks while H3N2 viruses have been decreasing.

Overall flu activity will likely remain elevated for several more weeks as viruses continue to circulate. CDC officials continue to recommend influenza vaccination for all individuals aged 6 months and older.

Reference

2017-2018 Influenza Season Week 8 ending February 24, 2018. Weekly US Influenza Surveillance Report. CDC’s website. https://www.cdc.gov/flu/weekly/index.htm. Accessed March 2, 2018.