Few answers yet on role of climate change with COVID-19
Could hot weather kill the new coronavirus?
As the reality of canceled events, school closures and social distancing sinks in, people are looking for an end date to all the havoc that efforts to control the virus are wreaking. And they’re hoping the president was right in predicting warm weather would make it go away.
COVID-19, the disease caused by the virus, could weaken with April’s warmer weather, President Donald Trump said in February during his White House address to governors.
But Maria Van Kerkhove, a COVID-19 technical lead with the World Health Organization, said in an early March news conference that there was no reason to believe that the virus would behave differently in different temperatures. Dr. Michael Ryan, executive director of the WHO’s Health Emergencies Programme, also spoke at the news conference and noted that the disease has been seen in a number of climates, including Singapore, which is hot and humid.
Some even worry that climate change and the way humans use resources are affecting the spread of such infectious diseases.
The bottom line: We don’t yet know how COVID-19 will respond to spring and summer conditions. A full year of seasons would be needed to truly understand COVID-19, said Dr. Peter Hotez, professor and dean for the National School of Tropical Medicine at the Baylor College of Medicine.
“This is a new virus, so we have no idea,” Hotez said. “Some people are conjecturing that it may diminish on the basis of what the flu does, which is another respiratory virus.”
He said COVID-19 may decline in the warmer months, or it may not be seasonal. It may also decline in the summer but not go away entirely and then come back in the fall. It could have a regular seasonal pattern every year, like the flu, or it may even be one-and-done.
People have long linked infectious diseases to the world around them. In the fifth century B.C., Greek physician Hippocrates observed that epidemics were associated with natural phenomena rather than deities or demons, according to a National Academies report titled Under the Weather: Climate, Ecosystems, and Infectious Disease.
The first pandemic of bubonic plague began in the 540s B.C. and “was preceded by a rare conjunction of three planets, which provided a convenient explanation for the extraordinary mortality,” the report said. But the bubonic plague of the 1340s showed that there was more to learn, as this epidemic wasn’t so easily linked to meteorological or cosmological phenomena.
The study of climate, weather and infectious disease has continued in various forms over the years, according to the report. And now that the epidemiological community has built the needed statistical and mathematical sophistication to address complex issues, such as potential health impacts of climate change, humanity is set to continue learning.
“It makes me wonder what we don’t know about infectious diseases,” said Dr. Hana Akselrod, assistant professor of medicine in the Division of Infectious Diseases at the George Washington University School of Medicine and Health Sciences, “and what a generation from now we will know from paying close attention to the natural world and bringing together the worlds of ecology, climate science and human health.”
Hotez, for instance, said the flu is known to be seasonal, as it peaks in the winter for the Northern Hemisphere and in the summer for the Southern Hemisphere. (It can be year-round in the tropics.) Yet, he said, researchers don’t truly understand what makes the flu seasonal — if it’s heat, humidity or something else.
One theory is that people are more likely to crowd inside together during colder weather. Another is that warmer air in spring and summer can accommodate higher humidity, and these larger microdroplets of water fall to the ground faster, maybe carrying the viruses to the ground before they can come into contact with a person’s face, Hotez said.
Akselrod added that immune systems are typically stronger in the summer than winter, partly because people spend more time outside and receive more vitamin D from the sun.
But it’s not just immediate weather conditions, such as flooding or droughts, that can impact infectious diseases. Researchers are also scrutinizing climate change and the way people use resources.
Valley fever, for instance, is caused by a fungus that lives in the soil of hot and dry regions in the southwestern U.S. And researchers believe that higher temperatures caused by climate change could prompt this infection to creep into Northern states and higher mountain elevations where physicians might not recognize the symptoms and quickly diagnose it.
Climate change might also play a role in emerging infections caused when an infected animal comes into contact with a person, which occurred with SARS, HIV and likely COVID-19.
And how might that animal get infected? Higher temperatures are prompting animals to move toward areas with cooler weather, coming into contact with other animals and with humans they might not have encountered before. That’s one way pathogens could be transferred, said Dr. Aaron Bernstein, the interim director of the Center for Climate, Health and the Global Environment at the Harvard T.H. Chan School of Public Health.
Diseases have also spread through the illegal trade of wildlife and the concentration of livestock when raised for food.
“If we want to prevent pandemics, we have to rethink how we do business with all life on Earth, in terms of how we harvest it and use it,” Bernstein said. “And we have to attack climate change. These are the primary preventive actions for pandemics.”