The CCP virus appears to weaken or die more readily when exposed to increasing amounts of sunlight, heat, or humidity, a U.S. Department of Homeland Security (DHS) official said.
William Bryan, the acting undersecretary of the science and technology for the DHS, said that government researchers have so far found that the virus survives best in indoor and dry conditions, and is less able to survive in hotter, more humid conditions.
“The virus dies quickest in the presence of direct sunlight,” he later said.
Practical Applications
At the news briefing on Thursday, Bryan shared research results headlined, “Increased temperature, humidity, and sunlight are detrimental to SARS-CoV-2 in saliva droplets on surfaces and in the air.”The results come from tests that the DHS has been carrying out at the National Biodefense Analysis and Countermeasures Center, a government biodefense research laboratory in Frederick, Maryland.
For nonporous surfaces such as steel, in a dark and low-humidity environment, the CCP virus has an 18-hour half-life—the time required for it to decrease by half, according to the researchers’ findings.
The half-life drops to six hours if the humidity is increased, with all other factors controlled. And when sunlight is further added to the equation, the half-life drops to about two minutes.
For aerosol-type conditions, such as when people cough or sneeze, the virus has a half-life of about an hour in dark, low-humidity conditions. Adding direct sunlight, however, decreases the virus’s half-life to one and a half minutes.
Bryan said that while there are “many unknown links in the COVID-19 transmission chain,” the trends observed so far can support practical decision-making to curb the spread of the CCP virus.”
Some practical applications include “increasing the temperature and humidity of potentially contaminated indoor spaces” to reduce the stability of the virus, and taking extra care for drier environments that don’t have sunlight, Bryan said.
Researchers have also found that bleach and isopropyl alcohol can kill the virus, with bleach taking about five minutes and isopropyl alcohol taking about 30 seconds, he said.
“And that’s with no manipulation—no rubbing—just spray it on and leaving it; you rub it, and it [the virus] goes away even faster,” Bryan said of the disinfectants’ application on the virus. The researchers are also experimenting with the effects of other disinfectants on the virus, Bryan added.
More than 874,000 people in the United States are confirmed to have been infected, and over 49,600 have died due to the CCP virus.
