Effects of Weather on Coronavirus Pandemic

Abstract

The novel coronavirus (SARS-CoV-2) has spread globally and has been declared a pandemic by the World Health Organization. While influenza virus shows seasonality, it is unknown if COVID-19 has any weather-related affect. In this work, we analyze the patterns in local weather of all the regions affected by COVID-19 globally. Our results indicate that approximately 85% of the COVID-19 reported cases until 1 May 2020, making approximately 3 million reported cases (out of approximately 29 million tests performed) have occurred in regions with temperature between 3 and 17 °C and absolute humidity between 1 and 9 g/m3. Similarly, hot and humid regions outside these ranges have only reported around 15% or approximately 0.5 million cases (out of approximately 7 million tests performed). This suggests that weather might be playing a role in COVID-19 spread across the world. However, this role could be limited in US and European cities (above 45 N), as mean temperature and absolute humidity levels do not reach these ranges even during the peak summer months. For hot and humid countries, most of them have already been experiencing temperatures >35 °C and absolute humidity >9 g/m3 since the beginning of March, and therefore the effect of weather, however little it is, has already been accounted for in the COVID-19 spread in those regions, and they must take strict social distancing measures to stop the further spread of COVID-19. Our analysis showed that the effect of weather may have only resulted in comparatively slower spread of COVID-19, but not halted it. We found that cases in warm and humid countries have consistently increased, accounting for approximately 500,000 cases in regions with absolute humidity >9 g/m3, therefore effective public health interventions must be implemented to stop the spread of COVID-19. This also means that ‘summer’ would not alone stop the spread of COVID-19 in any part of the world.

Weather Variability and COVID-19 Transmission: A Review of Recent Research

“…Following the initial outbreak in Wuhan, COVID-19 spread globally, with the majority of cases recorded in temperate regions in the northern hemisphere experiencing decreased temperatures and humidity [ 60 ]. This correlates with an optimal temperature range for transmission proposed by Huang et al and Bukhari et al, where recorded cases of COVID-19 were significantly associated with temperature in the ranges of 5–15 °C or 0 °C–17 °C and absolute humidity ranges of 1–9 g/m³ and 3–10 g/m³ respectively in the period up to May 2020 or the early stages of spring in the northern hemisphere [ 29 , 30 ]. Since May, as autumn and winter began in the southern hemisphere, cases have increased significantly, particularly in India and South America.…”

“…All included studies were peer-reviewed and published online by 1 October 2020. Of these studies, four studies were a global analysis of weather variables—two assessing distribution globally [ 29 , 30 ] and one evaluating association in 166 COVID-19 affected countries excluding China [ 31 ], and an early analysis of 100 affected countries [ 32 ]. The remaining articles were at the continent, country, state or city level ( n = 19/23) and included three from North America: one from New York, USA [ 33 ], one from Canada [ 34 ], and the third included selected counties in USA [ 35 ].…”

“…All studies assessing absolute humidity reported a significant association with COVID-19. Bukhari reported an optimal absolute humidity range, with the majority of reported cases between 1–9 g/m³, and Huang et al reported 73.8% of confirmed cases in regions with absolute humidity in the range of 3–10 g/m³ [ 29 ]. Liu et al reported a negative correlation between absolute humidity and confirmed case counts across 17 cities in China; when AH increased by 1 g/m³, cases decreased (when adjusted for onset lag of 7 days and 14 days) RR of 0.72 (95% CI: 0.59–0.89) and 0.33 (95% CI: 0.21–0.51) respectively [ 36 ].…”

“…Alkhowailed et al also reported a significant negative correlation with maximum and average wind speed ( p < 0.001 and p < 0.01, respectively) [ 44 ]. Bashir et al, Bukhari et al, Menebo, and Zhu et al did not report a significant association between wind speed and daily cases of COVID-19 [ 29 , 33 , 40 , 51 ].…”

Investigating the Potential for Ultraviolet Light to Modulate Morbidity and Mortality From COVID-19: A Narrative Review and Update

“…Important confounders to consider that may help resolve these inconsistencies in future studies include consideration of population demographics (e.g., age, gender, GDP, etc.) as well as local environmental and weather factors, particularly temperature and humidity ( 28 , 47 , 56 , 57 ). Indeed, a systematic review of 17 studies identified that places with warm and wet climates may reduce spread of SARS-CoV-2 ( 58 ).…”