Flu hospitalizations overtake Covid for first time.

CDC and HHS data capture an historic moment.

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For the first time since the Covid-19 pandemic erupted, influenza hospitalizations exceeded Covid-19 hospitalizations over a one-week period in the United States. The latest CDC data reflect reporting through the week ending November 26th.

Flu (October 2022-present) and Covid hospitalizations (March 2020-present). For week 47, flu hospitalized 4.2 per 100,000 people, compared to Covid’s 3.6 per 100,000. Note that the scale of the Covid hospitalizations is greater on its graph (The Y-axis peaks at 45 hospitalizations per 100,000 population, versus 12 per 100,000 on the flu graph; those are underlined in blue). Source: CDC FluSurv and CDC COVID-Net with annotations by Inside Medicine.

Data from HHS, meanwhile (whose data covers more hospitals) show flu hospitalizations exceeding last weeks’ Covid hospitalizations, though not yet overtaking Covid on a week-to-week basis.

The difference between the CDC and HHS numbers comes down to the difference in which hospitals their datasets cover. Either way, the conclusion is the same: For the first time, influenza and Covid are placing similar burdens on patients and the healthcare system. Notably, an RSV peak several weeks ago also exceeds the current Covid hospitalization rate, though its rate has fallen in the last couple of weeks; the most recent RSV hospitalization rate remains lower than either flu or Covid.

Image: Benjy Renton for Inside Medicine. Source: HHS.

The data: Comparing the CDC’s Covid and Influenza hospital surveillance systems shows that in week 47 of 2022 (week ending November 26), 4.2 influenza-related hospitalizations occurred for every 100,000 people, compared to 3.6 Covid-related hospitalizations for every 100,000 people. The two surveillance systems cover around 9-10% of the US population, and report on many of the same states. At its peak (the first week of January, 2022) there were 34.9 Covid-related hospitalizations for every 100,000 people, according to the CDC’s COVID-Net tracker.

Data from HHS indicate that in a handful of states, influenza hospitalizations exceeded Covid hospitalizations (around 98% of hospitals in the dataset reported both influenza and Covid deaths) in the last week.

Information on the severity of this influenza wave is starting to materialize. Currently, among the thousands of hospitals reporting to HHS, there are over 2,000 patients in intensive care units with influenza, and nearly 4,000 with Covid. However, both rates pale in comparison to ICU censuses recorded during at least three prior Covid peaks (we don’t have national data for the first wave, which at times topped 25,000 Covid patients in ICUs.

Image: Benjy Renton for Inside Medicine. Source: HHS.

That said, the weekly death rate from Covid remains higher than influenza, at least so far.

Image: Benjy Renton for Inside Medicine. Source: HHS.

A few words of analysis and explanation [The following section will be free to everyone in a few days]…