What’s Actually Driving Winter Surges of Covid-19?

New research suggests masking and social distancing remain the most important factors in preventing outbreaks

Photo: Florian Glawogger/Unsplash

Coronavirus cases and deaths rose throughout the United States in January. While it was predicted that the cold weather would fuel spikes by driving more people indoors, a new study suggests that the relaxing of non-pharmaceutical interventions (NPIs), like masking and social distancing, primarily drove the surge.

The relaxation of rules for mitigating Covid-19 and lower adherence to safety precautions play a larger role in wintertime outbreaks than bad weather, according to research from Princeton University published February 8 in Nature Communications. The researchers based their conclusions on a computer simulation of a wintertime coronavirus outbreak in New York City that aimed to determine the role of NPIs and climate in an outbreak. They found that if governments relaxed lockdown measures in the summer, there would be outbreaks in the winter, regardless of the weather.

“Our results implied that lax control measures — and likely fatigue with complying with control measures — would fuel wintertime outbreaks,” said Rachel Baker, PhD, an associate research scholar at Princeton’s High Meadows Environmental Institute (HMEI), in a press release.

Though many people have had Covid-19 at this point, most people are still susceptible to infection. “This means that if you roll back enforcement or adherence to control measures, you can still expect a large outbreak,” says Baker. “Climate factors including winter weather play a secondary role and certainly don’t help.”

Co-author Gabriel Vecchi, PhD, a professor of geosciences at HMEI, added that the virus currently spreads too quickly for climate to be a key factor in outbreaks any time of year, let alone the winter.

The findings may help explain why wintertime surges recently occurred in cities with temperate climates, such as Los Angeles and Phoenix.

This study was released as businesses in all but eight states — Hawaii, California, Colorado, Arizona, New Mexico, Oregon, Massachusetts, and Connecticut — are “mostly open,” according to the New York Times, and mask-wearing is not mandatory in a large number of states. While the Centers for Disease Control and Prevention maintains that masking, social distancing, and avoiding crowds are the best ways to stop transmission, it’s ultimately up to each state to make its own rules.



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Drew Costley

Drew Costley


Drew Costley is a Staff Writer at FutureHuman covering the environment, health, science and tech. Previously @ SFGate, East Bay Express, USA Today, etc.