Q&A: Do weather conditions influence the transmission of the coronavirus (SARS-CoV-2)? Is seasonality an important factor in COVID-19 transmission dynamics?

Updated: 22 May 2020

Answer

There is insufficient evidence to suggest that seasonality will play a role in transmission rates of SARS-CoV-2. At this phase of the pandemic, other factors are likely to be significantly more important, e.g. susceptibility in the population and mitigating behaviours. (May 10, 2020)

What does this mean?

The ability of SARS-CoV-2 to effectively spread globally, including in warm and humid climates, suggests that seasonality cannot be considered a key modulating factor of SARS-CoV-2 transmissibility at this time.

What can be done?

The COVID-19 disease is expected to remain present worldwide for a prolonged period of time. Interdisciplinary research on potential associations of COVID-19 transmission and impacts with weather and environmental conditions, such as air quality, should continue exploring these associations. Efforts that encourage international data sharing and research collaboration, the harmonization and use of good practices in study design and data collection will improve future research and knowledge.

Evidence

This is an area of active research. The impact of climate and seasonality on the SARS-CoV-2 novel coronavirus is not definitively known. Several research teams are investigating the correlation between environmental variables such as temperature, humidity, and UV radiation, and the number of cases of COVID-19. These studies have not been peer-reviewed, and there are many other factors to consider that may be influencing disease transmission under different climates, including connectivity from locations with a high incidence, population susceptibility and surveillance for respiratory infections. There is a growing body of research on the connections between climate and other viruses, including other coronaviruses and influenza. In this research, investigators have found evidence that virus transmission might decline with higher humidity or temperatures, depending on the virus. This provides some expectation that SARS-CoV-2 transmission might slow under warmer temperatures. However, SARS-CoV-2 might not show these same sensitivities. Moreover, the disease dynamics of COVID-19--a rapidly spreading pandemic meeting a naive global human population--are quite different from these other diseases. 

Additional Reading

Q&A: Climate change and COVID-19
World Health Organization (April 22, 2020)

Rapid Expert Consultation on SARS-CoV-2 Survival in Relation to Temperature and Humidity and Potential for Seasonality for the COVID-19 Pandemic (April 7, 2020)
US National Academies of Sciences, Engineering and Medicine

Do weather conditions influence the transmission of the coronavirus (SARSCoV- 2) (March 23, 2020)
Oxford COVID-19 Evidence Service Team

O'Reilly, K.M., Auzenbergs, M., Jafari, Y., Liu, Y., Flasche, S. and Lowe, R., 2020. Effective transmission across the globe: the role of climate in COVID-19 mitigation strategies. The Lancet. Planetary Health.

Seasonality of SARS-CoV-2: Will COVID-19 go away on its own in warmer weather? (March 2020)
Harvard T.H. Chan School of Public Health Center for Communicable Disease Dynamics

Coronavirus disease 2019 (COVID-19) pandemic: increased transmission in the EU/EEA and the UK – seventh update (March 25, 2020)
European Centre for Disease Prevention and Control Global

Tools

Monthly Climate Explorer for COVID-19 Application
Copernicus Climate Change Service (C3S)