Linking Outdoor Air Temperature and SARS-CoV-2 Transmission in the US Using a Two Parameter Transmission Model

Ty Newell

Research output: Working paper


Outdoor temperature lower than 50F and greater than 70F is shown to nearly double the transmission efficiency of the SARS-CoV-2 virus. Outdoor temperature is an important factor behind the current surge in US Covid-19 cases. Correlation of northern state infection data and outdoor temperatures is used to identify the change in disease transmission efficiency as northern states passed through the lower temperature bound (50F) in spring, and more recently transitioned to temperatures above the higher bound (70F). At current disease transmission efficiency levels, social distancing must be increased above a UMD Social Distance Index (SDI) level of 36 to stop the accelerated increase of daily infection cases. At current disease transmission efficiency (G=0.19) and SDI of 33, the US will approach 150,000 infections per day in September before declining as average US temperature falls below 70F. A primary reason for enhanced disease transmission below 50F and above 70F is attributed to inadequate indoor ventilation. Swing season occurs when outdoor temperatures are between 50F and 70F, and is the time of year when homes and buildings are opened to the outdoors. Increased fresh air ventilation (greater than 40cfm per person), improved air filtration (MERV11 and greater filters), and UVGI (Ultraviolet Germicidal Irradiation, 0.02WUV per cfm airflow) coupled with wearing face masks, 6ft distancing and surface sanitation are estimated to reduce indoor disease transmission probability to a third of the transmission probability resulting from standard building ventilation practice.Competing Interest StatementThe authors have declared no competing interest.Funding StatementNo funding has been received for this work.Author DeclarationsI confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.YesThe details of the IRB/oversight body that provided approval or exemption for the research described are given below:All relevant ethical guidelines have been followed. No IRB or ethics committee approvals were required for this work. All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived.YesI understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.YesAll data used in the analyses are cited and available
Original languageEnglish (US)
PublisherCold Spring Harbor Laboratory Press
Number of pages34
StateIn preparation - Jul 25 2020

Publication series



  • Coronavirus
  • COVID-19
  • severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
  • Novel coronavirus
  • 2019-nCoV
  • Pandemic


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