Can Warmer Weather Slow COVID-19 Spread?
Sun, April 18, 2021

Can Warmer Weather Slow COVID-19 Spread?


After the World Health Organization declared novel coronavirus a pandemic, many countries and organizations have become more focused on creating a vaccine since only a vaccine can prevent people from acquiring the virus. Recent statistics gathered by show that COVID-19 cases have reached 721,224 with a death toll of 33,940. The US and Italy are the countries with the most cases as of now with 141,732 and 97,689, respectively, overtaking China with 81,439. 

Early estimates by China’s National Health Commission (NHC) showed that about 80% of those who died from COVID-19 were over the age of 60, with 75% of them having pre-existing health conditions such as cardiovascular diseases and diabetes. A recent study of 138 hospitalized patients with NCIP also revealed that the median age of cases detected outside China was 56 years (interquartile range, 42-68; range, 22-92 years) and 75 (54.3%) were men. 

Since there’s currently no cure for COVID-19, health officials advise that the best protection against infection and spreading are non-pharmaceutical interventions. This includes hand washing, sanitizing surfaces, social distancing and staying home when feeling ill. According to The Guardian, an online British site, about 35 companies and academic institutions are racing to create such a vaccine. At least four of them have already tested the vaccine in animals. 



As the world continues to cope with the onset of COVID-19, a growing body of research suggests a link between higher temperatures and decreased transmission rates of coronavirus. This link started due to the fact that many of the largest outbreaks have been in regions where the weather is cooler. Since the coronavirus first emerged in China around mid-December, the virus has spread quickly, with the number of cases now rising most sharply in the US and Europe. Previous studies have also suggested a link between the two. 

A study conducted by Kate Templeton from the Center for Infectious Diseases at the University of Edinburgh about 10 years ago discovered that three coronaviruses showed “marked winter seasonality,” which means they seemed to cause infections mainly between December and April. An unpublished analysis suggests a link between the spread of the virus and temperature, wind speed and relative humidity after comparing the weather in 500 locations around the world where there have been COVID-19 cases. 



Will Warm Weather Kill COVID-19?

Researchers from the Massachusetts Institute of Technology (MIT) set out to explore the supposed link between high temperatures and decreased coronavirus cases. "Based on the current data on the spread of 2019-nCoV [or SARS-CoV-2, which causes the illness COVID-19], we hypothesize that the lower number of cases in tropical countries might be due to warm humid conditions, under which the spread of the virus might be slower as has been observed for other viruses," the researchers said.

Elizabeth McGraw, director for the Center for Infectious Disease Dynamics at Pennsylvania State University, stated that coronaviruses tend to be associated with winter because they are spread. We are more likely to see spikes in transmission rates of respiratory during winter conditions due to the nature of the virus. For instance, Influenza thrives in colder, dry conditions such as those present during winter in the northern hemisphere, helping the virus to spread more easily from person to person.

While warmer and wetter weather might not kill the virus, new preliminary research suggests such conditions could hamper the ability of the virus to infect people. According to Business Insider, a fast-growing business site with deep financial, media, tech, and other industry verticals, the findings suggest that for each degree in temperature increase and each percent humidity increase, the contagiousness of the disease caused by the coronavirus decreases. "It indicates that the arrival of summer and rainy season in the Northern Hemisphere can effectively reduce the transmission of the COVID-19," the authors wrote.

The experts used R0, which refers to the average number of people that one sick person goes on to infect among a group that has no immunity to the virus, to predict how far and how fast a disease will spread. They found out that the coronavirus' R0 value decreased by 0.04 and 0.02, respectively, for every 1.8-degree Fahrenheit increase in temperature and a 1% increase in relative humidity. Thus, if the virus has an R0 value of 2, an 18-degree Fahrenheit increase would drop the R0 value to 1.6 - a 20% decrease. 

According to The New York Times, an American newspaper based in New York City with worldwide influence and readership, the researchers discovered that most coronavirus transmissions had occurred in regions with low temperatures, between 37.4 and 62.6 degrees Fahrenheit. On the other hand, regions with average temperatures above 64.4 degrees Fahrenheit account for fewer than 6% of global cases so far. 

“Wherever the temperatures were colder, the number of the cases started increasing quickly. You see this in Europe, even though the health care there is among the world’s best,” co-author Qasim Bukhari, a computational scientist at MIT, said. 



Why the Warmer Months May Not Help

Unfortunately, there’s still a possibility that warmer weather may not impact infection rates. Since none of the recent studies have been peer-reviewed by other scientists, Bukhari acknowledged that factors such as social distancing measures, travel restrictions, variations in the availability of tests and hospital burdens might have affected the number of cases in different countries.

According to EcoWatch, a leading environmental news site engaging millions of concerned individuals every month, countries with warmer temperatures such as Argentina, Brazil, and Australia are still seeing their share of confirmed cases during their summer. They also reported increasing rates of infection. "The short answer is that while we may expect modest declines in the contagiousness of SARS-CoV-2 in warmer, wetter weather and perhaps with the closing of schools in temperate regions of the Northern Hemisphere, it is not reasonable to expect these declines alone to slow transmission enough to make a big dent," Marc Lipsitch, professor of epidemiology and director at the Center for Communicable Disease, said. 

Instead of relying on warmer weather to expect the declines of coronavirus transmission rates, Dr. Matthew Ferrari, Associate Professor of Biology at Penn State Center for Infectious Disease Dynamics, stated that physical distancing, hygiene, testing, and reinforcing health systems are the only measures anyone can take. "If we, or any country, put the testing and health infrastructure in place to respond, then hopefully the need for severe physical distancing, and the associated social and economic costs, won’t be as dire,” he said.