Absolute humidity and transmission of COVID-19

Absolute humidity and transmission of COVID-19. Jefferson T,  Heneghan C.


Published on June 19, 2020

Reference Luo et al. The role of absolute humidity on transmission rates of the COVID-19 outbreak. Luo et al. 2020. The role of absolute humidity on transmission rates of the COVID-19 outbreak. https://www.medrxiv.org/content/10.1101/2020.02.12.20022467v1 2020
Study type
Country SE Asia
Setting Global
Funding Details Not reported
Transmission mode Meteorological
Exposures Absolute humidity, temperature

Bottom Line

Changes in weather alone will not necessarily lead to declines in COVID-19 case counts without the implementation of extensive public health interventions.

Evidence Summary

There was a positive correlation between absolute humidity and growth and a weak negative correlation between temperature and growth.

What did they do?

The study assesses whether high absolute humidity may limit the survival and transmission of Covid 19. The authors collected cumulative incidence data from a variety of sources for the period January 23, 2020 (day of Wuhan lockdown) to February 10, 2020 and compared it with data from Thailand, Singapore, Japan, South Korea, Hong Kong, Taiwan and other regions of China. They estimated the reproductive number as an indicator of case growth and correlated it to absolute humidity by conversion from relative humidity.

All the data used for this study is publicly available as reported in the manuscript.

Study reliability

The estimates were calculated using likely incomplete reported case count data, with the date of reporting, rather than date onset, which adds uncertainty to the estimates.

Clearly defined setting Demographic characteristics described Follow-up length was sufficient Transmission outcomes assessed Main biases are taken into consideration
Yes No No Partly No

What else should I consider?

The report is based on early preliminary data and appears to have been assembled in haste with part of the “Limitations” text missing.  The short time length combined with imperfect data reporting practices makes the results uncertain and vulnerable to change as more data is available.

About the authors

Carl Heneghan

Carl is Professor of EBM & Director of CEBM at the University of Oxford. He is also a GP and tweets @carlheneghan. He has an active interest in discovering the truth behind health research findings

Tom Jefferson

Tom Jefferson, epidemiologist.