MIT scientists say humidity 'sweet spot' may help reduce spread of COVID-19

LOS ANGELES - Previous research has indicated that proper indoor ventilation helps reduce the spread of COVID-19. Now, researchers at MIT have found a "sweet spot,"  in indoor humidity which they say can reduce the transmission of the novel coronavirus. 

In the study published on Nov. 16, 2022, in the Journal of the Royal Society Interface, researchers report that maintaining an indoor relative humidity between 40 and 60 percent attributed to lower rates of COVID-19 infections and deaths. MIT researchers noted that most people are comfortable at around 30 and 50 percent relative humidity. Airplane cabins are typically about 20 percent. 

To find this sweet spot, researchers analyzed data from 121 countries, from January 2020 through August 2020. Researchers say that whenever a specific region experienced a spike in COVID-19 deaths or cases, the relative humidity in that region, on average was either lower than 40 percent or higher than 60 percent regardless of the season. 

"There’s potentially a protective effect of this intermediate indoor relative humidity," suggests lead author Connor Verheyen, a PhD student in medical engineering and medical physics in the Harvard-MIT Program in Health Sciences and Technology.

"Indoor ventilation is still critical," says co-author Lydia Bourouiba, director of the MIT Fluid Dynamics of Disease Transmission Laboratory and associate professor in the departments of Civil and Environmental Engineering and Mechanical Engineering, and at the Institute for Medical Engineering and Science at MIT. "However, we find that maintaining an indoor relative humidity in that sweet spot — of 40 to 60 percent — is associated with reduced Covid-19 cases and deaths."

Meanwhile, The World Health Organization chief on Nov. 9, reported a nearly 90% drop in recent COVID-19 deaths globally compared to nine months ago provides "cause for optimism," but still urged vigilance against the pandemic as variants continue to crop up.

Director-General Tedros Adhanom Ghebreyesus said that last month just over 9,400 deaths linked to the coronavirus were reported to the WHO. In February of this year, he said, weekly deaths had topped 75,000 globally.

"We have come a long way, and this is definitely cause for optimism. But we continue to call on all governments, communities and individuals to remain vigilant," he said at a virtual news conference from the WHO’s Geneva headquarters.

So is the coronavirus on its way out? 

You might think so. New, updated booster shots are being rolled out to better protect against the variants circulating now. The U.S. Centers for Disease Control and Prevention has dropped COVID-19 quarantine and distancing recommendations. And more people have thrown off their masks and returned to pre-pandemic activities.

But scientists say no. They predict the scourge that’s already lasted longer than the 1918 flu pandemic will linger far into the future.

One reason it’s lasted this long? It’s gotten better and better at getting around immunity from vaccination and past infection. Scientists point to emerging research that suggests the latest omicron variant gaining ground in the U.S. — BA.4.6, which was responsible for around 8% of new U.S. infections last week — appears to be even better at evading the immune system than the dominant BA.5.

Scientists worry the virus may well keep evolving in worrisome ways.

How long will it be around?

White House COVID-19 coordinator Dr. Ashish Jha said COVID-19 will likely be with us for the rest of our lives.

Experts expect COVID-19 will someday become endemic, meaning it occurs regularly in certain areas according to established patterns. But they don’t think that will be very soon.

Still, living with COVID "should not necessarily be a scary or bad concept," since people are getting better at fighting it, Jha said during a recent question-and-answer session with U.S. Sen. Bernie Sanders of Vermont. "Obviously if we take our foot off the gas — if we stop updating our vaccines, we stop getting new treatments — then we could slip backwards."

Experts say COVID will keep causing serious illness in some people. The COVID-19 Scenario Modeling Hub made some pandemic projections spanning August 2022 to May 2023, assuming the new tweaked boosters adding protection for the newest omicron relatives would be available and a booster campaign would take place in fall and winter. In the most pessimistic scenario — a new variant and late boosters — they projected 1.3 million hospitalizations and 181,000 deaths during that period. In the most optimistic scenario — no new variant and early boosters — they projected a little more than half the number of hospitalizations and 111,000 deaths.

The Associated Press contributed to this story.