That means indoor sports games can turn into superspreader events, the researchers said in the US Centers for Disease Control and Prevention’s weekly report.
The game was played on June 16 at an ice rink in Tampa and by the following day, a player, considered the index patient, experienced symptoms of Covid-19, including fever, cough, sore throat and a headache. Two days later, he tested positive for the virus, the Florida Department of Health reported.
Coronavirus spreads at hockey game
Each team had 11 players, all male, between the ages of 19 and 53, with six on the ice and five on the bench at any given time during the game, the researchers reported. Each team also shared separate locker rooms, typically for 20 minutes before and after the 60-minute game, and no one wore cloth face masks for disease control.
“During the five days after the game, 15 persons experienced signs and symptoms compatible with coronavirus disease 2019; 13 of the 15 ill persons had positive laboratory test results indicating infection with SARS-CoV-2, the virus that causes COVID-19,” researchers wrote. Two of the sick individuals did not get tested.
While 62% of the players experienced Covid-19 symptoms, the on-ice referees did not, nor did the one spectator in the stands.
Ice rink well-suited to Covid-19 transmission
Ice hockey involves vigorous physical exertion with heavy respiration during the game and frequent contact between the players.
“The ice rink provides a venue that is likely well suited to COVID-19 transmission as an indoor environment where deep breathing occurs, and persons are in close proximity to one another,” the researchers noted.
More than one player may have been infectious during the game, the researchers acknowledged, but they believe that the index patient was the source of the transmission while he was still asymptomatic.
The median incubation time for Covid-19 is four to five days from exposure to symptom onset and ranges from two to 14 days, according to the CDC.
The analysis was limited because not all the players were tested for the virus and asymptomatic infections may not have been identified.
“The indoor space and close contact between players during a hockey game increase infection risk for players and create potential for a superspreader event, especially with ongoing community COVID-19 transmission,” the study concluded.
“The ice rink provides a venue that is likely well suited to COVID-19 transmission as an indoor environment where deep breathing occurs, and persons are in close proximity to one another,” they added.
Sparse information on Covid-19 spread at sports events
There are few published studies or reports on Covid-19 transmission associated with specific sports games or practices, other than what has been reported in the news, the CDC noted.
In New Hamphire, 158 residents associated with 23 different ice hockey teams or organizations have been diagnosed with Covid-19 over the past two months, Dr. Benjamin Chan, the state epidemiologist, said Thursday. Of the 158 cases, 117 have been linked to separate outbreaks and 41 are not related to a specific outbreak, but are connected to ice hockey, Chan said. “Hockey has been one of the high-risk activities where we have seen substantial spread,” Chan added.
People who are believed to have contracted coronavirus through their association with hockey have also potentially exposed others in at least 24 different K-12 schools in the state, he said, noting that the game is increasing the risk of exposure and spread to other facilities and organizations.
On Thursday, New Hampshire Gov. Chris Sununu ordered all ice activities at indoor facilities halted for the for the next two weeks.
Other potential superspreader events
Other documented cases of a superspreader event include a choir in Washington last spring where 53 out of 122 members of the Skagit Valley Chorale contracted the virus and two died after attending two rehearsals in March.
“The act of singing, itself, might have contributed to transmission through emission of aerosols, which is affected by loudness of vocalization,” a report on the event by the CDC found.
Some public health experts have called a Rose Garden ceremony at the White House in late September a superspreader event after dozens who attended the event contracted the coronavirus, including President Donald Trump and members of his administration, although it’s unclear exactly where the President first became infected.
The coroanvirus has also spread through meat processing plants and was linked to an outbreak involving 57 participants in a high-intensity fitness dance class in South Korea.