COVID-19: Temperature, humidity and latitude analysis to predict potential spread and seasonality

COVID-19: Temperature, humidity and latitude analysis to predict potential spread and seasonality.  Jefferson T, Spencer E, Heneghan C

https://www.cebm.net/study/covid-19-temperature-humidity-and-latitude-analysis-to-predict-potential-spread-and-seasonality/

Published on June 19, 2020

Reference Sajadi et al. Temperature, humidity and latitude analysis to predict potential spread and seasonality for COVID-19. http://dx.doi.org/10.2139/ssrn.3550308 2020
Study type
Country Global
Setting Public
Funding Details NIH & intramural
Transmission mode Meteorological
Exposures Latitude, temperature, humidity

Bottom Line

The transmission of COVID-19 is associated with the 30 to 50 degree N’ longitude corridor and weather patterns and low specific and absolute humidity.

Evidence Summary

Cities with consistent transmission had varying relative humidity (44-84%), but consistently low specific (3-6 g/kg) and absolute humidity (4-7 g/cubic mt).

All the cities with significant outbreaks as of March 10, 2020 had low average temperatures around 5 to 11 degrees centigrade and specific humidity compared to other cities without COVID-19 cases. 

The distribution of the significant outbreaks along restricted latitude, temperature, and humidity are consistent with the behaviour of a seasonal respiratory virus. The authors point out that the meteorological conditions had been stable for at least a month before the outbreaks and speculate that the conditions may favour the stabilization of the droplet and enhanced viral propagation in the nasal mucosa.

What did they do?

The study tested the correlation between Covid-19 incidence (community transmission) and humidity and temperature along the observed longitude corridor. It charts the spread along the corridor which has consistently similar temperatures and humidity levels

  • Meteorological data were based on data from the ECMWF ERA-5 obtained from Climate Reanalyzer (https://ClimateReanalyzer.org), 
  • Climate Change Institute, University of Maine, USA. ERA-Interim reanalysis data (https://doi.org/10.1002/qj.828). 
  • ERA-5 reanalysis data (C3S, 2017) covers the earth with a resolution of 30 km x 30 km. daily updates are available with 5 days of real-time; quality-assured monthly updates are published within 3 months of real-time. 
  • COVID-19 country-wide data was obtained from Johns Hopkins CSSE.
  • Significant community transmission was defined as > 10 reported deaths in a country as of March 10, 2020. 

ClimateReanalyzer.org

Study reliability

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 surveillance efforts in the tropics, as well as the Southern Hemisphere between the months of June through September, may be of value in verifying the impact of meteorological variables.  The authors point out that we need a better understanding of seasonality for coronaviruses and other acute respiratory viruses, and that environmental sample testing from areas of ongoing infection, and closes epidemiological and climate studies should be undertaken. 

As an example see: Effects of air temperature and relative humidity on coronavirus survival on surfaces. Appl Environ Microbiol 2010; 76(9): 2712-7. 

About the authors

Carl Heneghan

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

Elizabeth Spencer

Elizabeth Spencer

Dr Elizabeth Spencer; MMedSci, PhD. Epidemiologist, Nuffield Department for Primary Care Health Sciences, University of Oxford.

Tom Jefferson

Tom Jefferson

Tom Jefferson is a senior associate tutor and honorary research fellow, Centre for Evidence-Based Medicine, University of Oxford.