As cases of COVID-19 surge in several warm-weather states, public health experts are pointing to the easing of state and local government restrictions and the recent spate of demonstrations as likely transmitters.
But there is another possible culprit: air conditioning.
“There is a seasonal effect, spread of [the coronavirus] is less efficient in heat and humidity. But in many parts of the U.S. you’re getting a reverse seasonal effect,” former head of the Food and Drug Administration Scott Gottlieb tweeted Friday. “It’s 110 degrees in Phoenix, 95 degrees in Houston. People are going indoors for air conditioning.”
Fourteen states have recorded their highest seven-day average of new COVID-19 cases since June 1: Alaska, Arizona, Arkansas, California, Florida, Kentucky, New Mexico, North Carolina, Mississippi, Oregon, South Carolina, Tennessee, Texas, and Utah.
A Washington Examiner analysis of the largest cities in those states found that a dozen had at least three days from June 1-14 when the temperature reached at least 90 degrees. The two exceptions are Anchorage, Alaska, and Portland, Oregon.
Topping the list was Phoenix, Arizona, where all 14 days reached at least 90 degrees, and 10 days topped 100. Arizona has seen an average of more than 1,300 new coronavirus cases a day in the last week. Over that same period, the number of people hospitalized due to COVID-19 has increased by nearly 400. On Saturday, Arizona health director Cara Christ told hospitals to “fully activate” emergency plans to deal with the surging number of cases.
Houston, Texas, was a close second, with 13 days reaching at least 90 degrees. Houston Mayor Sylvester Turner said the city is considering a new stay-at-home order in response to rising cases. He also said he was considering establishing a hospital at a football stadium for coronavirus patients.
Transmission of the coronavirus is greater indoors.
“I think it is the case that indoor transmission is much more likely than outdoor transmission under the virus,” said Dr. Amesh Adalja, an infectious disease expert and senior scholar at the Johns Hopkins Center for Health Security. “As businesses open up and it gets really hot outside, people are more likely to sit inside a restaurant.”
One reason air conditioning may be a potent transmitter has to do with lower humidity and cooler air. Studies of mice, for instance, have found that ones in areas of higher humidity have an easier time fighting off the influenza virus.
“Air conditioning has a few effects on viral transmission,” said Erin Bromage, a comparative immunologist and professor of biology specializing in immunology at the University of Massachusetts Dartmouth. “The virus remains active for longer in cooler air. With lower humidity, below 40%, the virus can stay in the air for longer.”
Bromage also noted that the impact of more people sharing cool, recirculated air due to high temperatures from one to two weeks ago would only start emerging in the COVID-19 data now as the virus has a five- to 10-day latency period.
The airflow caused by air conditioning may also increase the risk of transmission. Chinese researchers examined an outbreak of COVID-19 traced to a restaurant in Guangzhou, China. Of the 83 customers in the restaurant at that time, 10 later tested positive for COVID-19. One of them had just traveled from the Wuhan province. All 10 were clustered around three tables that were in the direct airflow of the restaurant’s air conditioning.
The research, published in the journal Emerging Infectious Diseases, concluded that “transmission was prompted by air-conditioned ventilation. The key factor for infection was the direction of the airflow.”
But Adalja is cautious about the implications of that study.
“It doesn’t really fit, epidemiologically, with what we’re seeing,” he said. “It’s in the realm of possibility that this occurred [due to air conditioning]. But it is hard to know exactly how applicable it is to all other cases and how much of it was very specific to what was going on in that restaurant.”
Nashville, Tennessee, which had seven days of at least 90-degree temperatures, has paused its reopening. Mayor John Cooper announced Thursday that the city will remain in phase two of its reopening.
In addition to Nashville, the states of Utah and Oregon paused the reopening of their economies on Thursday. Other cities in the above-listed states that are considering a pause are Austin, Texas, and Miami, Florida.
The post Air conditioning eyed as culprit in warm-weather-state coronavirus transmission appeared first on Washington Examiner.