COVID-19 is a highly communicable disease, but evidence suggests that small gatherings indoors and households are where the new coronavirus is spreading the fastest.
For nearly a year, public health officials around the world have been grappling with how to reduce the spread of COVID-19. Sometimes travel is restricted, schools and gyms are closed, and some cities, such as San Francisco, are closed. But despite these limitations, the number of COVID-19 infections and deaths continues to hit record highs.
“I think we want to be careful about blaming a particular environment and scapegoating a particular environment for transmission generation,” said Dr. John Brownstein, an ABC News employee, epidemiologist and chief innovation officer at Boston Children’s Hospital.
However, there are some settings where COVID-19 is more easily distributed. For example, in New York, contact tracing has shown that 70% of new cases come from small gatherings and households.
“In fact, informal gatherings may have played the biggest role,” Brownstein said, “because they are harder to control, more difficult to maintain, and people are likely to be more lax when it comes to recommendations for wearing masks and social distancing.”
When people gather in small groups with friends and family, they are more likely to let go of their vigilance, not wear their mask, and stay indoors longer, making it easier to transmit the virus.
In a recent study at the University of Mississippi Medical Center, researchers found that for children and adolescents who tested positive for COVID-19, small social gatherings – not school – were the most likely place they were exposed to the virus. .
The children who tested positive in the study were more likely to attend out-of-home social gatherings, play dates, or have visitors at home where precautions for mask wearing and social distance were not taken.
Early in the pandemic, after initial lockdowns eased and the number of cases began to increase, contact tracing also linked the spread of the virus to restaurants and bars.
In a study published by the Centers for Disease Control and Prevention, people who eventually tested positive for COVID-19 were twice as likely to have eaten in a restaurant in the past two weeks compared to participants who did not test positive for the virus.
“The obvious challenge is losing an important control, wearing a mask,” said Dr. Joseph Allen, an assistant professor of exposure assessment science at Harvard TH Chan School of Public Health. “Because you have a restaurant with a lot of people talking loudly [with] masks, which leads to higher emissions of respiratory aerosols and, depending on how that ventilation system in the restaurant works, determines how many infectious aerosols people breathe. “
As with small home gatherings, people in restaurants often eat with people who are not in their immediate household and do not wear masks, and are in a confined space with poor ventilation.
“Gyms have generally done a good job of adhering to protocols,” said Brownstein. “We don’t see many super spreader events related to gyms … because the protocols they had to establish regarding social distance, mask wearing, and ventilation were pretty good overall.”
Schools are another environment where many people are usually in a closed environment. Educational institutions have struggled with decisions about providing in-person classroom instruction or distance learning to reduce transfer.
But Brownstein said schools were generally safe. “Of course there are outliers,” he added, “but we have seen good evidence that schools have spent time developing a protocol in which social distance and mask wearing have done a relatively good job.”
There is also a lot of guidance regarding ventilation in schools that make the environment safer, Allen said.
Ultimately, when it comes to what drives high transmission speeds in both homes and restaurants, it’s “the similarity in the underlying factors,” Allen said. “Time indoors, no masks, little or no ventilation.”
For weeks, experts have been warning of the wave of new infections to come with Thanksgiving trips. We see that now. The looming wave of travel and small indoor gatherings over the longer holiday week between Christmas and New Year couldn’t come at a worse time, experts warn. However, certain measures can help.
“There is no panacea when it comes to interventions. It’s kind of a layered approach,” said Brownstein. “Social distancing and wearing a mask … indoor ventilation, restrictions on gatherings … If people adhere to these general public health guidelines in the broad sense of the word, they have really succeeded in reducing transmission. . “
Adjoa Smalls-Mantey, MD, D.Phil., Trained in immunology and a psychiatrist in New York City. She is also a contributor to the ABC News Medical Unit.