Temperature, Humidity, and Latitude Analysis to Estimate Potential Spread and Seasonality of Coronavirus Disease 2019 (COVID-19)

Abstract

Importance: Coronavirus disease 2019 (COVID-19) infection has resulted in a global crisis. Investigating the potential association of climate and seasonality with the spread of this infection could aid in preventive and surveillance strategies.

Objective: To examine the association of climate with the spread of COVID-19 infection.

Design, setting, and participants: This cohort study examined climate data from 50 cities worldwide with and without substantial community spread of COVID-19. Eight cities with substantial spread of COVID-19 (Wuhan, China; Tokyo, Japan; Daegu, South Korea; Qom, Iran; Milan, Italy; Paris, France; Seattle, US; and Madrid, Spain) were compared with 42 cities that have not been affected or did not have substantial community spread. Data were collected from January to March 10, 2020.

Main outcomes and measures: Substantial community transmission was defined as at least 10 reported deaths in a country as of March 10, 2020. Climate data (latitude, mean 2-m temperature, mean specific humidity, and mean relative humidity) were obtained from ERA-5 reanalysis.

Results: The 8 cities with substantial community spread as of March 10, 2020, were located on a narrow band, roughly on the 30° N to 50° N corridor. They had consistently similar weather patterns, consisting of mean temperatures of between 5 and 11 °C, combined with low specific humidity (3-6 g/kg) and low absolute humidity (4-7 g/m3). There was a lack of substantial community establishment in expected locations based on proximity. For example, while Wuhan, China (30.8° N) had 3136 deaths and 80 757 cases, Moscow, Russia (56.0° N), had 0 deaths and 10 cases and Hanoi, Vietnam (21.2° N), had 0 deaths and 31 cases.

Conclusions and relevance: In this study, the distribution of substantial community outbreaks of COVID-19 along restricted latitude, temperature, and humidity measurements was consistent with the behavior of a seasonal respiratory virus. Using weather modeling, it may be possible to estimate the regions most likely to be at a higher risk of substantial community spread of COVID-19 in the upcoming weeks, allowing for concentration of public health efforts on surveillance and containment.

Figure 1.. World Temperature Map, November 2018 to March 2019

Color gradient indicates 2-m temperatures. Black circles represent countries with substantial community transmission (ie, ≥10 deaths as of March 10, 2020). Image from Climate Reanalyzer.

Figure 2.. World Temperature Map, January 2020 to February 2020

Color gradient indicates 2-m temperatures, based on data from the European Centre for Medium-Range Weather Forecasts ERA-5 reanalysis. White circles represent countries with substantial community transmission (ie, ≥10 deaths as of March 10, 2020), and red isolines indicate areas with temperatures between 5 and 11 °C. Generated using Copernicus Climate Change Service Information 2020.

Figure 3.. Temperature vs Humidity Plot for 50 Cities With and Without COVID-19

Temperatures and specific humidity are mean values obtained from cities between 20 and 30 days before first community death for cities with substantial community outbreaks of COVID-19. Other cities with and without COVID-19 outbreaks were similarly analyzed, with benchmarks being first community spread–related death (when available) or last day of data collection (March 10, 2020). Orange circles represent countries with substantial community transmission (≥10 deaths as of March 10, 2020), and circle size represents total cases in each country. eTable 2 in the Supplement has characteristics of the 50 cities included.

Figure 4.. Comparison of Mean Temperature and Humidity Between Cities and Countries With COVID-19

A-C, Mean 2-m temperature, mean specific humidity, and mean relative humidity were compared with the Mann-Whitney test between cities with and without substantial community transmission. Dots indicate values for cities with nonsubstantial transmission, and squares indicate values for cities with substantial transmission. Substantial community transmission was defined as at least 10 reported deaths in a country as of March 10, 2020. D-F, mean 2-m temperature, mean humidity, and mean relative humidity in representative cities were analyzed by linear regression against log of total cases in 50 different countries with and without COVID-19 (eTable 2 in the Supplement). Countries with 0 cases were assigned 0.5 cases. Circles represent values from individual cities.

Figure 5.. World 2-m Mean Temperature Map, March to April 2019, Estimating At-Risk Zone for March to April 2020

Color gradient indicates mean 2-m temperatures, except neon green band, which shows a zone with temperatures between 5 and 11 °C and specific humidity between 3 and 6 g/kg. The tentative zone at risk for substantial community spread in the near term includes land areas within the neon green bands and will change based on actual mean temperatures during this period and other factors. Image from Climate Reanalyzer.