US government researchers have determined that the virus survives best indoors and in dry conditions, and loses potency when temperatures and humidity rise – and especially when it is exposed to sunlight, said William Bryan, acting head of the US Department of Homeland Security’s Science and Technology Directorate.
Coronavirus appears to weaken more quickly when exposed to sunlight, heat and humidity, a US official said on Thursday in a potential sign that the pandemic could become less contagious in summer months.
“The virus dies quickest in the presence of direct sunlight,” he told a White House news briefing, according to Reuters.
The findings could bolster hopes that the coronavirus will mimic the behavior of other respiratory diseases like influenza, which typically are less contagious in warm weather.
But the coronavirus has also proven lethal in warm-weather places like Singapore, raising broader questions about the impact of environmental factors.
President Donald Trump said the findings should be interpreted cautiously, but also claimed vindication for previously suggesting that the coronavirus might recede in summer.
“I once mentioned that maybe it does go away with heat and light. And people didn’t like that statement that much,” he said at the briefing.
More than 874,000 people in the United States are known to have been infected and over 49,600 have died of COVID-19, the highly contagious respiratory illness caused by the novel coronavirus, according to a Reuters tally.
On nonporous surfaces like stainless steel, the new coronavirus takes 18 hours to lose half its strength in a dark, low-humidity environment, Bryan said.
In a high-humidity environment, that half-life dropped to six hours, and when the virus was exposed to high humidity and sunlight, the half-life dropped to two minutes, he said.
Researchers found a similar effect with the coronavirus that was suspended in the air – simulating the coughing or sneezing that often spreads the disease. In a dark room, the virus maintained half its strength for an hour. But when exposed to sunlight, it lost half its strength in 90 seconds, Bryan said.