A study about an outbreak of COVID-19 in a group predominantly made up of healthcare professionals in Alberta was published Tuesday, shining a spotlight on the role socializing may have played in the spread of the virus.
The outbreak at the Annual Western Canadian Medical Bonspiel in Edmonton in 2020 took place in the early days of the pandemic and was one of the first large-scale outbreaks in the province.
The study, which was published in CMAJ Open, dissects the event, discusses the likely route of transmission and uncovers the infectivity during the sporting and social event.
The peer-reviewed article comes as the province enters Step 1 of re-opening, which will see the return of indoor restaurant dining, one-on-one personal training, school-related children’s sports and limited school and minor sport training, which was added on Saturday.
The bonspiel took place between March 11 and 14, 2020, when there were only 24 confirmed cases of COVID-19 in Alberta. Of the 73 curlers at the event, 54 were confirmed or probable cases – an attack rate of 74 per cent. Curlers were mainly physicians from Alberta, Saskatchewan, Manitoba and Ontario.
The study, which consisted of telephone interviews, found 10 participants identified having mild symptoms, such as fatigue, sore throat and diarrhea and ingestion, during the bonspiel.
“None of these individuals had symptoms consistent with the clinical case definition used by public health authorities at the time, and three had travelled internationally before the event,” the paper reads.
Two curlers withdrew after the first day and one did not participate on the final day because of their mild symptoms.
Dr. Kelly Burak, lead author of the study and bonspiel participant, said this finding emphasizes the importance of being aware of symptoms and to stay home and get tested if sick.
Burak said it was natural, as an epidemiologist, to conduct a study of the event after the first case was confirmed. He himself contracted COVID-19 and acknowledged there are regrets about holding the event.
“The only thing we could do about that is study it, learn from it and share that experience with others.
“I think it’s really, really important not to feel ashamed by what happened but own it, say we’ve got to learn from this and others can learn from this, and that’s the whole idea of why we did this study,” he said.
Burak said analysis of the outbreak highlights the importance of public health measures. At the time, there was no recommendation about masking in indoor spaces in Alberta; at the event, curling rocks were cleaned between games and participants were not shaking hands.
The study found that a “significantly” greater proportion of symptomatic participants attended the buffet lunches at the curling rink.
“Our data suggest that attending buffet lunches in the curling rink lounge may have been important for transmission,” the article reads.
“The single team with no confirmed cases did not attend any social events outside of their curling games, suggesting that social activities associated with sporting events may be as, or more important, for transmission.”
Burak said this finding highlights the importance of congregating in groups when food and drink are being shared without wearing a mask.
“Our experience shows that some of the risk is involved with the socializing before or after the actual sporting event. People have to be really careful when they’re doing that.
“They have to be really aware when you are around others, including sporting events – wearing a mask may be necessary, be vigilant about washing hands and not socializing, interacting with people for long periods of time before or after the sporting events,” he said.
Epidemiologist Cynthia Carr, with EPI Research Inc. in Winnipeg, was not involved with the bonspiel or the study.
Carr reviewed the study and said she was struck by how no members of the team who did not attend the dining or social events were infected.
“Given the quite high attack rate of the rest of the group, that seems to tell me that that’s not a coincidence.
“It seems to show that the socialization and the eating together in particular is a very much, higher-risk situation than the actual sporting event itself,” Carr said.
“We just need to be careful that we don’t take away from this study an indication of risk associated with a sporting event because that’s not what this study is saying. It’s saying a sporting event with socialization.”
Burak said the situation now where the province is reopening as variant cases climb, which he finds concerning, is reminiscent of the experience at the bonspiel.
“Our cases at the time were all linked to travel in Alberta. There wasn’t community transmission and it very rapidly took off.
“Now we’re dealing with a more infectious variant – I just feel like it’s déjà vu all over again,” he said.
‘Something was coming’
Dr. Daisy Fung, a family physician in Edmonton, was one of the participants at the bonspiel. After a positive case was confirmed at the bonspiel, Fung went into quarantine.
Four days in, Fung started to develop symptoms – a fever of 41C for almost a week and fatigue.
Fung said, at the time of the bonspiel, participants were paying close attention to the news and changes with public health restrictions.
“It was still pretty normal feeling but with a sense of maybe something was coming,” she said.
Meals at the bonspiel were held indoors and were buffet-style.
“Because of those shared utensils, buffet-style, being indoors, of course we weren’t wearing masks at the time we were eating or the time we were congregating in the buffet area. That was probably the big source of the spread,” she said.
“Now I worry with the new variant being even more infectious and opening up dining again indoors, people are obviously not going to be wearing masks while they’re eating, understandably so, I do have concerns about how much this new variant will spread.
“As community spread rises, the chances that spread will sneak into a long-term care facility for a first, or heaven forbid, a second outbreak, I fear that greatly.”
Serology results show that of the 40 confirmed cases, 30 had positive serology; of the 14 probable cases, seven had positive serology.
One confirmed case with only anosmia, also known as smell loss, had no antibodies two months after the event.
“Other studies have liked the severity of symptoms to the probably of antibodies developing. In the other four confirmed cases with negative serology, serology was done quite late (115, 194 207, 220 days), and may represent the waning of antibodies titres over time,” the study reads.
Carr said there’s information emerging about how well having an infection actually protects an individual.
“It’s important for people that have had COVID-19 to remember a natural exposure to a virus does not necessitate that you will have the same level of antibodies or same level of immunity.
“Whether that’s by not being able to get it again at all or not getting as sick, that has to come from a vaccine,” Carr said.
The authors acknowledge the limitations of the study include a small sample size, the variability of COVID-19 testing in the country at the time and that self-reporting may have led to bias.