LAUSR

Professional soccer athletes are at risk of acquiring SARS-CoV-2 when traveling or through domestic community transmission. The U.S. Major League Soccer (MLS) league uses protocol-based SARS-CoV-2 testing for identification of individuals with COVID-19. Per MLS protocol, fully vaccinated players underwent SARS-CoV-2 RT-PCR testing weekly; unvaccinated players were tested every other day. Demographic and epidemiologic data (e.g., travel history) were collected from individuals who tested positive, and contact tracing was performed. Whole genome sequencing (WGS) was performed on positive specimens, and phylogenetic analyses were used to identify potential transmission patterns. In the fall of 2021, all 30 players from one MLS team underwent SARS-CoV-2 testing per protocol; 27 (90%) were vaccinated. One player who recently traveled to Africa tested positive for SARS-CoV-2; within the following two weeks, 10 additional players and 1 staff member without recent international travel history tested positive. WGS yielded full genome sequences for 10 samples, including one from the traveler. The traveler’s sample was Delta sublineage AY.36 and was closely related to a sequence from Africa. Nine samples yielded other Delta sublineages including AY.4 (n = 7), AY.39 (n = 1), and B.1.617.2 (n = 1). The seven AY.4 sequences clustered together; five were identical, suggesting a common source of infection. Transmission from a family member visiting from England to an MLS player was identified as the potential index case. The other two AY.4 sequences differed from this group by 1-3 nucleotides, as did a partial genome sequence from an additional team member. WGS is a useful tool for understanding SARS-CoV-2 transmission dynamics in professional sports teams.