A new rapid expert consultation from a standing committee of the National Academies of Sciences, Engineering, and Medicine responds to questions from the White House Office of Science and Technology Policy (OSTP) regarding survival of the COVID-19 virus in relation to temperature and humidity and potential for seasonal reduction and resurgence of cases.
Natural history studies published so far have conflicting results regarding potential seasonal effects on the virus, and they are hampered by poor data quality, geography-related confounding factors such as access to and quality of health care and the availability of diagnostics, and insufficient time since the beginning of the pandemic from which to draw conclusions, the rapid expert consultation says. There is some evidence to suggest that the COVID-19 virus may transmit less efficiently in environments with higher ambient temperature and humidity; however, given the lack of immunity to the virus globally, this reduction in transmission efficiency may not lead to a significant reduction in disease spread without the simultaneous adoption of major public health interventions.
Given that countries currently in “summer” climates, such as Australia and Iran, are experiencing rapid virus spread, a decrease in cases with increases in humidity and temperature elsewhere should not be assumed. Additional studies as the pandemic unfolds could shed more light on the effects of climate on transmission, the rapid expert consultation says.
Although experimental studies show a relationship between higher temperatures and humidity levels and reduced survival of the COVID-19 virus in the laboratory, there are many other factors besides environmental temperature, humidity, and survival of the virus outside of the host that influence and determine transmission rates among humans in the ‘real world.’
The National Academies Standing Committee on Emerging Infectious Diseases and 21st Century Health Threats, assembled in early March at the request of OSTP and the U.S. Department of Health and Human Services’ Office of the Assistant Secretary for Preparedness and Response in response to the COVID-19 outbreak, has been providing rapid expert consultations on several topics, such as social distancing, severe illness in young adults, and crisis standards of care.
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