Abstract
The resumption of professional sports during the COVID-19 pandemic has been described in team sports but less in individual sports. The International Biathlon Union implemented a COVID-19 concept for the 2020-2021 season aimed to mitigate the risks of transmission by rules designated for the professional biathlon environment. The "bubble" model was based on regular reverse transcript polymerase chain reaction (PCR) testing with rapid results and efficient result management protocol. The objective of this study was report incidence and transmission of SARS-CoV-2 among professional biathletes and staff undergoing frequent PCR testing and risk reduction measures during the international season 2020-2021. The efficiency of risk mitigation measures was also evaluated based on the incidence data. During the 4-month season, altogether 22,182 SARS-CoV-2 PCR tests were conducted on all individuals participating in international biathlon season (athletes, team staff and organizing committee). Ninety-six (0.4%) PCR tests were positive and 30% of the positive PCR tests were considered "persistent positive" following recovery from a recent COVID-19 infection. No transmission events were detected following contact with "persistent positive" cases during the season. A great majority of the positive PCR tests were recorded during the first days after arrival in the "bubble", often in the first entry test taken by the on-site laboratory. In conclusion, a "bubble model" based on frequent PCR testing and hygiene rules was efficient in keeping the infection rate low. The competition activity including international travel was safe, and most of the infections seemed to originate from outside of the "bubble".