Outpatient visits for influenzalike illness (ILI), which includes influenza, SARS-CoV-2, and RSV, were higher after 3 weeks than for any of the previous five flu seasons:through the CDC’s Outpatient Influenza-like Illness Surveillance Network involved ILI as of Oct. 22. The highest comparable rate in the previous 5 years was the 1.9% recorded in late October of 2021, shortly after the definition of ILI was changed to also include illnesses other than influenza.
This season’s higher flu activity is in contrast to the previous two, which were unusually mild. The change, however, is not unexpected, as William Schaffner, MD, an infectious disease expert and professor of preventive medicine at Vanderbilt University,.
“Here we are in the middle of October – not the middle of November – we’re already seeing scattered influenza cases, even hospitalized influenza cases, around the country,” he said. “So we know that this virus is now spreading out in the community already. It’s gathering speed already. It looks to me to be about a month early.”
One indication of the mildness of the previous two flu seasons was the number of deaths, both pediatric and overall. Influenza-associated pediatric deaths had averaged about 110 per season over the previous eight seasons, compared with just 1 for 2020-2021 and 43 in 2021-2022.
Other indicators of early severity
This season’s early rise in viral activity also can be seen in hospitalizations. The cumulative rate of flu-related admissions was 1.5 per 100,000 population as of Oct. 22, higher than the rate observed in the comparable week of previous seasons going back to 2010-2011, according to the CDC’s Influenza Hospitalization Surveillance Network.
A look at state reports of ILI outpatient visit rates shows that the District of Columbia and South Carolina are already in the very high range of the CDC’s severity scale, while 11 states are in the high range. Again going back to 2010-2011, no jurisdiction has ever been in the very high range this early in the season, based on data from the Outpatient Influenza-like Illness Surveillance Network.