Birthday celebrations raised the risk of spreading SARS-CoV-2 by 30% last year in U.S. counties with high rates of COVID-19, according to a new study. No such surge was seen in places with low rates of infection.
For the study, researchers at Harvard Medical School and the RAND Corporation analyzed health insurance claims data from nearly 3 million U.S. households in the first 45 weeks of 2020. Overall, households with recent birthdays averaged 8.6 more cases of COVID for every 10,000 people than households in the same counties without a birthday.