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. 2024 Nov 22;4(1):244.
doi: 10.1038/s43856-024-00633-5.

Morbidity of SARS-CoV-2 in the evolution to endemicity and in comparison with influenza

Istvan Bartha  1 , Cyrus Maher  2 , Victor Lavrenko  2 , Yi-Pei Chen  2 , Qiqing Tao  2 , Julia di Iulio  2 , Keith Boundy  2 , Elizabeth Kinter  2 , Wendy Yeh  2 , Davide Corti  2 , Amalio Telenti  3
Affiliations

Morbidity of SARS-CoV-2 in the evolution to endemicity and in comparison with influenza

Istvan Bartha et al. Commun Med (Lond). .

Erratum in

Abstract

Background: There are three possible SARS-CoV-2 post-pandemic scenarios: (i) ongoing severity, (ii) influenza-like severity, and (iii) a transition to an endemic disease with lesser morbidity similar to that of other human coronaviruses.

Methods: To assess a possible evolution of the pandemic under the three scenarios, we use data from the US National Covid Cohort Collaborative, CDC COVID-NET, and CDC Fluview and from the WastewaterSCAN Dashboard. We include influenza disease and treatment response as benchmark. The US National Covid Cohort Collaborative allows the quantification of viral-specific morbidity using electronic health records from 424,165 SARS-CoV-2 cases, 53,846 influenza cases, and 199,971 uninfected control subjects from 2021-2022. Evolution of hospitalization rates is estimated from the correlation between national SARS-CoV-2 and influenza hospitalization data and viral gene copies in wastewater.

Results: Our findings reveal that medically attended SARS-CoV-2 infections exhibit similar morbidity to influenza [indicative of scenario (ii)], but SARS-CoV-2 hospitalization rates are one order of magnitude lower than influenza when considering virus concentration in wastewater [indicative of scenario (iii)]. Moreover, SARS-CoV-2 displays a more favorable response to antiviral therapy.

Conclusions: Our analysis confirms a rapid decline in SARS-CoV-2 morbidity as it transitions to an endemic state.

Plain language summary

The impact of SARS-CoV-2 infections has changed over time since the start of the pandemic. We use information about deaths and hospitalization from COVID-19 and combine it with data obtained from monitoring wastewater to study how patterns of infection have changed over time and how this compares with the impact of influenza. We show that recently there has been a marked decrease in SARS-CoV-2 infections leading to hospitalization, in contrast to stable rates of hospitalization for people infected with influenza. Our results suggest that SARS-CoV-2 is currently a persistent, i.e., endemic disease with less severe impact on most people who are infected. This information is helpful for hospitals and public health departments that monitor and prepare for infectious disease outbreaks.

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Conflict of interest statement

Competing interests: The authors declare the following competing interests: Authors are employees or contractors of Vir Biotechnology Inc., San Francisco, CA, USA.

Figures

Fig. 1
Fig. 1. Excess morbidity in the post-acute period.
Estimated odds ratios for having a new disease manifestation during acute infection and up to 3 months after infection compared to uninfected patients during a selected control period. a (SARS-CoV-2) and b (influenza), control period is an arbitrary period not necessarily linked to a medical contact. c (SARS-CoV-2) and d (influenza), control period is a period marked by an arbitrary non-infectious medical attended event. For each organ manifestation or disease, the figure provides three odds ratio estimates that correspond to three consecutive periods: days 0–28 (orange), 29–56 (blue) and 57–84 (green) after infection.
Fig. 2
Fig. 2. Effectiveness of antiviral treatment.
Estimated odds ratios for the effect of SARS-CoV-2 (a) or influenza (b) antiviral treatment against severe manifestations of acute infection and acute and post-acute morbidity. For each organ manifestation or disease, the figure provides three estimates that correspond to three consecutive periods/months: days 0–28 (orange), 29–56 (blue) and 57–84 (green).
Fig. 3
Fig. 3. Estimation of evolving morbidity using wastewater data.
Morbidity is here defined as the rates of hospitalization in reference to the levels of virus in wastewater. Nationwide SARS-CoV-2 and influenza hospitalization cases are obtained from the US Centers for Disease Control and Prevention. Wastewater viral gene copies are obtained from WasteWater SCAN (see Methods). Wastewater viral gene copies are shown non-normalized (a, c, e, g) or normalized (b, d, f, h) to PMMoV (Pepper mild mottle virus). Best fitted regression lines for nationwide hospitalization rates to viral gene copies in wastewater for each SARS-CoV-2 pandemic wave (a, b) and two influenza seasonal epidemics (e, f) are shown. c and d are the slopes of panels a and b for each wave, showing that the morbidity has a decreasing trend over time for SARS-CoV-2. g and h are the slopes of panels e and f, showing that influenza has stable morbidity for the 2022–2023 and 2023–2024 seasons. N in a, b, e and f correspond to the number of weeks for which there are correlation data between hospitalization rates to viral gene copies in wastewater (shown after each equation). The error bars of c, d, g and h represent the standard errors of the regression coefficients of the best fitted lines.
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