Profile - Karl Fix

Experts game to explore COVID-19 in athletes

Out­door trans­mis­sion of COVID-19 among rugby play­ers ap­pears to be lower than ini­tially thought, ac­cord­ing to re­searchers study­ing the rate of in­fec­tion among ath­letes.

When the NBA suddenly suspended its season a year ago after one of its athletes tested positive for COVID-19, it was just the start of a series of shutdowns that affected more than just team sports. A year later, many professional sports leagues have resumed activity, bolstered by strict COVID protocols and a robust and expensive testing strategy that can't be matched by community leagues designed for fun and fitness, not profit.

Initially, there was concern about letting professional sports resume, given that the risk of virus transmission between athletes in match and practice situations is thought to be high. Most team sports require repeated close contact between players who are breathing heavily without wearing masks — the antithesis of social distancing. But for researchers trying to find out more about how the coronavirus is transmitted in an athletic milieu, the resumption of activity in a limited and controlled manner has offered a unique opportunity to evaluate how sports contribute to the spread of the virus between teammates.

Two recent papers published in the British Journal of Sports Medicine (BJSM) studied the transmission of the coronavirus in rugby and soccer.

The Rugby Football League in the U.K. restarted at the beginning of August, forgoing the scrum (when players press close together with their heads down and battle for possession of the ball), but keeping the rest of the game true to its original form, including close-contact tackles. Games involved two teams of 17 each and three officials, with players tested weekly for the virus. Athletes were required to have a negative test within seven days prior to a match and were screened daily for symptoms.

Inevitably, some players tested positive or demonstrated symptoms consistent with the coronavirus within 48 hours after a match. Game statistics, video playback and GPS data were used to identify all contacts the infected players had with other athletes on the field, with contact defined as faceto-face interaction inside of one metre for more than three seconds.

Of the 36 league games played, eight athletes in four matches tested positive or displayed symptoms within 48 hours after a game. Twenty-eight players were then identified as high risk for catching the virus due to their interactions (measured in frequency and accumulated time) with one of those eight athletes, and were told to isolate. One hundred other players participated in the matches but were not required to isolate due to lack of close contact with the infected players.

Within the isolation period, one of the 28 players deemed at high risk to become infected, tested positive. Five others who played in one of the four matches but were not considered at high risk also tested positive. Yet all six infected players were thought to have contracted the virus from an unrelated internal club outbreak or community transmission, rather than on the field of play.

“There were other players and other members of staff within that club that also tested positive that weren't involved in the match, so that seems a more probable explanation,” lead researcher Ben Jones said in a BJSM podcast discussing his findings.

That's not the only reason Jones suggested the virus transmission occurred off the field of play. The one athlete identified as high risk who eventually tested positive was involved in 30 tackles, which seems in keeping with on-field transmission. But another player in the same match who was involved in 32 tackles with infected athletes didn't develop COVID -19.

This inconsistency in transmission despite a similar or even greater risk of exposure was enough for the research team to suggest that interactions taking place off the field (locker rooms, team meetings, travelling together in cars, etc.) were more likely to be responsible.

“What this actually means for our understanding of the virus transmission is the outdoor transmission risk even during tackles is probably lower than we first thought,” said Jones.

A study of 1,337 professional soccer players in Qatar yielded a similar conclusion despite 36 players testing positive for COVID -19 — an infection rate the researchers claim “was consistent with that of the general population during the same time period.”

“Social contacts and family were the most common sources of infection, and no infection could be traced to training or matches,” said the researchers. “Football (soccer) played outdoors involving close contact between athletes represents a limited risk for SARS-COV-2 infection and severe illness when preventive measures are in place.”

Despite those conclusions, both sets of researchers said they aren't comfortable stating that there is absolutely no risk of transmission during on-field contact in an outdoor setting, but agree that off-field behaviours are more likely to spread the virus.

What does that mean for community sports leagues hoping to start up again soon? Public health guidelines stating that outdoor sports are safer than indoor sports seem to be validated, as is the recommendation to close locker-rooms and other indoor areas where teammates gather. So more outdoor recreational leagues may be allowed to operate this summer, which is great news for sports enthusiasts of all ages itching to get back on the field.