Investigating the effects of absolute humidity and movement on COVID-19 seasonality in the United States

  1. Gary Lin
  2. Alisa Hamilton
  3. Oliver Gatalo
  4. Fardad Haghpanah
  5. Takeru Igusa
  6. Eili Klein

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Abstract

Mounting evidence suggests the primary mode of SARS-CoV-2 transmission is aerosolized transmission from close contact with infected individuals. While transmission is a direct result of human encounters, falling humidity may enhance aerosolized transmission risks similar to other respiratory viruses (e.g., influenza). Using Google COVID-19 Community Mobility Reports, we assessed the relative effects of absolute humidity and changes in individual movement patterns on daily cases while accounting for regional differences in climatological regimes. Our results indicate that increasing humidity was associated with declining cases in the spring and summer of 2020, while decreasing humidity and increase in residential mobility during winter months likely caused increases in COVID-19 cases. The effects of humidity were generally greater in regions with lower humidity levels. Given the possibility that COVID-19 will be endemic, understanding the behavioral and environmental drivers of COVID-19 seasonality in the United States will be paramount as policymakers, healthcare systems, and researchers forecast and plan accordingly.

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  1. Version published to 10.1038/s41598-022-19898-8
  2. ScreenIT

    SciScore for 10.1101/2020.10.30.20223446: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    Studies of prior viruses and preliminary studies of the SARS-CoV-2 virus underpin the theoretical connection between humidity and transmission; however, limitations remain in assessing this association. One limitation of this study includes the spatial coupling of populations due to travel and commute, which may alter the transmission patterns within counties. Spatial clustering of the analysis by trends in humidity should reduce this effect somewhat. A second limitation is an intra-county heterogeneity of the population (i.e., income, demographics, and social status), which we attempted to control for with fixed effects in our model. Third, as with most COVID-19 analyses on retrospective data, heterogeneity in testing at the county level likely results in differences in the correlation between reported results and actual cases. Fourth, other exogenous events, such as evacuation-related activities related to natural disasters or mass-gatherings in several cities this summer (52), may bias the connection between humidity and transmission. Finally, there may also be time-varying trends in other factors that affect case detection rates, though GAMs reduce the potential impact of these factors as they account for time-varying trends related to unobservable factors external to the independent variables in the model. The upcoming winter in the United States and other temperate regions in the northern hemisphere are likely to increase transmission of SARS-CoV-2 due to falling humidi...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

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  3. Version published to 10.1101/2020.10.30.20223446 on medRxiv