Coronavirus: Does warm weather slow the spread of the virus? Maybe

President Donald Trump said last week that he believed that COVID-19, the new coronavirus that is spreading around the globe, will “go away” by April as the weather gets warmer in the United States.

Trump was criticized by many for making the claim, but recent research on the COVID-19 virus appears to show that temperature and humidity can make a difference in the ability of the virus to continue to infect large numbers.

According to a study uploaded to the medical pre-print server MedRxiv on Monday, it appears that a correlation exists between warm weather and a decrease in the transmission rate of the coronavirus.

If the climate conditions are extremely cold or very hot and humid, the virus is “largely absent,” the study showed. The results of the study were reported by Bloomberg News on Monday.

According to the study, people in tropical and polar climates are unlikely to see local transmission of COVID-19 cases.

Researchers wrote that between June and September, much of Europe and North America should see a slowing rate of infections.

Another study, by Beijing-based researchers, uploaded to the pre-print server arXiv last week came to a similar conclusion. It should be noted that neither study has been reviewed by other researchers.

A study published in 2011 that looked at other coronaviruses also showed that higher temperatures and humidity tend to result in the viruses dying more quickly.

Dr. Alan Evangelista, a microbiology and virology professor at St. Christopher’s Hospital for Children in Philadelphia, told ABC News that studies he has conducted found results similar to the other studies.

Evangelista said his research showed, “As humidity increases, the viral droplet size is larger and settles out of the air rapidly.”

COVID-19 is believed to be spread by viral droplets that are injected into the air when a person coughs or sneezes, and them land on someone nearby. “In contrast, in low humidity, there is rapid evaporation of respiratory droplets,” he continued. “They remain airborne for prolonged periods, increasing the time and distance over which transmission can occur.”

Evangelista, who has studied common coronaviruses and influenza particles for eight years, said his work indicates that because of the size of the droplet, “transmission is highly efficient under drier and colder conditions,” but far less so in a humid environment.

While the results seem promising for a slowdown of the virus’ transmission as the weather gets warmer, other researchers question whether weather conditions actually have a great effect on the virus’ ability to spread.

“While we may expect modest declines in the contagiousness of [the novel coronavirus] in warmer, wetter weather,” according to Dr. Marc Lipsitch, a Harvard epidemiologist, “it is not reasonable to expect these declines alone to slow transmission enough to make a big dent.”

As of Tuesday, more than 5,900 Americans have tested positive for COVID-19, with the disease killing 99.

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