Children’s birthday parties are meant to be fun and harmless affairs, but a recent study shows they may be partly to blame for the spread of COVID-19.
The study, published in the Journal of the American Medical Association, collected private health insurance information from 2.9 million U.S. households from the first 45 weeks of 2020. In counties with high rates of COVID-19 transmission, households were 31% more likely to test positive for the virus within two weeks after someone’s birthday.
In households where a child’s birthday occurred, there were 15.8 more positive coronavirus tests per 10,000 people. After an adult’s birthday, that number plunged to only 5.8 positive tests per 10,000 people.
This can likely be attributed to the higher rate of children’s birthday parties versus adult birthday parties.
The study found no differences stemming from factors like milestone birthdays, county political leaning, precipitation, or shelter-in-place policies. Households in states with stay-at-home orders were just as likely to test positive after a birthday, and the correlation between birthdays and positive tests was just as strong in areas that voted for former President Donald Trump in 2016 compared with those that did not.
The U.S. has totaled more than 33 million COVID-19 cases and almost 600,000 deaths due to the virus, according to the Centers for Disease Control and Prevention COVID Data Tracker.
From March 1 through May 31, 2020, stay-at-home or shelter-in-place orders were issued in 42 states and territories, according to data from the CDC.
Informal social gatherings like children’s birthday parties are an important source of COVID spread, according to Dr. Timothy Brewer, a professor of medicine and epidemiology at the University of California. He was not involved in the study.
“While people are doing a good job or a better job of social distancing or wearing their masks when they go to a supermarket, when they get home they’re more likely to relax and not necessarily wear masks or social-distance,” Brewer said.