The COVID-19 pandemic is entering a critical phase, with governors and scientists hopeful that warmer, wetter weather tamps down transmission while cautioning that it’s too soon to ease social distancing and other social restrictions.
Spring and summer humidity can ruin a picnic, but it also yanks infectious droplets to the ground.
The moisture that surrounds the virus when it is expelled from an infected person tends to evaporate quickly in colder months, allowing the virus to float in the air. Dry air can also make it harder for people to clear the virus from their nasal passages.
The science isn’t ironclad — COVID-19 is newly discovered — but similar viruses tend to recede in the summer and pick up when dry air returns in the fall.
“We do anticipate some seasonality. The viruses, when it’s humid and hot, are not as transmissible from person to person,” said William Schaffner, an infectious disease specialist at Vanderbilt University.
“But it’s not a sure thing and, as I like to quip, I don’t know if COVID-19 has, quote, read the textbook and knows what to do,” he said. “We have to plan for the shady side of the street, not just the sunny side.”
The Pennsylvania Department of Health said the potential for a summertime easing did not factor into Gov. Tom Wolf’s three-phase plan for returning to normal operations. Instead, the governor’s plan relies on current data and conditions.
“We have seen cases decrease in some parts of the state but not in others, despite temperatures starting to warm,” department spokesman Nate Wardle said. “It remains to be seen if this virus is one that is seasonal or if it is hardy enough to thrive no matter the temperature.”
Likewise, Michigan officials said their modeling “is not evaluating the potential effects of seasonality yet.”
“We are regularly looking at social distancing data and will continue that as summer progresses,” state Health and Human Services Department spokeswoman Lynn Sutfin said.
Summer has downsides, too, when it comes to COVID-19.
Air conditioning reduces humidity, meaning the physics around droplets won’t always apply, and Chinese researchers concluded that nine diners sitting in the path of an air conditioner’s airflow were infected by a single person at a Guangzhou restaurant this year.
The Centers for Disease Control and Prevention said restaurant owners should consider spacing out tables and keeping their eateries well-ventilated.
Even if the virus does wane, scientists at the White House podium are talking about a resurgence in autumn that will coincide with the influenza season, making predictions more complicated and forcing the federal government and states to plan for the whole year.
President Trump once hoped the virus would dissipate in April as temperatures rose. That didn’t happen. Infections have soared, and the U.S. death toll is nearing 50,000.
New York Gov. Andrew Cuomo said Thursday that 438 people died in his state during the most recent 24-hour reporting period.
“That number is not coming down as fast as we would like to see that number come down,” said Mr. Cuomo, a Democrat.
Like everyone else, Mr. Cuomo is wondering what will happen in the summer and fall.
“No one’s really saying it will go away when the weather gets warm … but there’s still a theory the virus could slow during the summer but then come back in the fall. If it comes back in the fall, it then comes back with the normal flu season,” Mr. Cuomo said. “That’s then problematic because you’re then testing for flu and testing for COVID-19. … That could be a possible overwhelming of the testing system.”
New York is digging in for a long fight, though some states are trying to determine whether they can ease shutdown orders and reopen restaurants, gyms, salons and other businesses.
Anice Lowen, an associate professor at the Emory School of Medicine, said communities “certainly should not bank on seasonality being a help in the summer.”
For one thing, we may be too susceptible to this new disease for climate to matter much.
“Unlike more typical coronaviruses where immunity constrains spread, this virus is brand new to the human population and very few people have immunity. In light of this, physical distancing and masks are critical,” she said.
Scientists are tracking the spread of the virus in the Southern Hemisphere, which is nearing its winter. The virus will likely maintain itself there during the Northern Hemisphere’s summer.
“This would in turn allow the virus to move back into the temperate climates of the Northern Hemisphere during our early winter months, creating a seasonality in the pattern,” said Anthony Amoroso, an associate professor at the University of Maryland School of Medicine.
Anthony Fauci, a top scientist on the White House coronavirus task force, said COVID-19 is likely to circulate around the globe for some time, fueling cycles in the U.S. and underscoring the need for a vaccine.
“We will have coronavirus in the fall,” he said at midweek. “I am convinced of that because of the degree of transmissibility that has the global nature.”
