Nine months into the COVID-19 pandemic, health officials still face a conundrum that’s as vexing as it was at the beginning of the outbreak: pinning down how cases are being spread in the community.
In Ontario, as many as 60 per cent of cases have unknown sources of transmission.
The lack of data has, in part, led to our current lockdown, as government advisers look to the U.S. for information on how far it is necessary to go in shutting down parts of the economy.
“Restaurants have done all they have been asked and more. Officials are making decisions based on theories and suppositions. But the financial and reputational harms on this industry are not theoretical. They are all too real,” said James Rilett, a spokesperson for Restaurants Canada, a not-for-profit association that advocates for the food service industry.
Frustration with the province’s decision to send Toronto and Peel Region into lockdown prompted backlash from business owners this week, with some opening in defiance of health measures and others calling for big-box stores that were deemed essential services to be shuttered.
One of the reasons for the lack of data on where community spread is occurring is that it’s exceedingly difficult to do contact tracing of strangers in crowded places like restaurants, bars and gyms. Surging case numbers in recent weeks have made contact tracing in some areas, like Toronto and Peel, nearly impossible. (In early October, Toronto Public Health announced it was suspending contact tracing outside of high-risk situations and institutional outbreaks because of the increasing number of cases in the broader community.)
But researchers on the COVID-19 science advisory table, a group of scientists and health policy experts who analyze trends and advise the provincial government, say there’s enough evidence from U.S. studies and local outbreak data to make educated guesses about where the virus is most likely to spread.
“It is most likely that a lot of what goes undetected in the statistics and in contact tracing, even if people try hard, happens in those indoor spaces where people meet most,” said Dr. Peter Juni, scientific director of the science advisory table and a professor of medicine and epidemiology at the University of Toronto.
“Indoor gatherings where people are relatively close to each other — it can be you and your friends; it doesn’t have to be other people who you don’t know — and where people stay for a prolonged period of time, meaning more than 15 minutes, that’s actually what’s happening with indoor dining.”
In a report earlier this month, the advisory table made a link between the frequency of visits to restaurants with indoor dining and the potential to spread the virus if those establishments reopened.
The report also shows that while less than 10 per cent of COVID-19 cases in Ontario are linked to outbreaks, restaurants, bars, ceremonies and religious services make up a combined nine per cent of those outbreaks. Settings with the most outbreaks are long-term-care and retirement homes (26.5 per cent) and schools and daycares (22.2 per cent).
“It doesn’t mean that the proportion shown in those figures for restaurants covers everyone who was infected in a restaurant; it just covers the ones we know about,” said Beate Sander, co-chair of Ontario’s COVID-19 modelling consensus table. “This large proportion of community transmission does happen in schools, in restaurants and in gyms and in workplaces and … everywhere, basically.”
A snapshot of data from Toronto Public Health shows that during one week in September, there were 45 active outbreaks in workplace settings, 18 of them in restaurants and bars, another in a nightclub and one more in an adult entertainment club.
“Combined, these outbreaks represented 44 per cent of our community outbreak investigations alone,” said Dr. Vinita Dubey, Toronto’s associate medical officer of health, in an email, adding that the investigations “were incredibly resource-intensive.”
“Bars and restaurants have large volumes of contacts to trace,” she said, “with some of these venues having more than 500 contacts to notify, and with one having 1,700 patrons to reach.”
The province closed indoor dining, bars, gyms and theatres in Toronto, Peel and Ottawa on Oct. 10. Gyms were allowed to reopen earlier this month before being shut down again in Toronto and Peel under the new lockdown, which also closed outdoor dining, hair salons and non-essential retail.
Dubey said the strategy behind the current lockdown is to limit the ability of people to spend time together in high-risk environments where the chance of infection is heightened.
“This is a difficult choice, but a necessary one at this time,” she said.
When asked if there was any evidence to close down restaurant patios, as Toronto and Peel did this week, the Ministry of Health said in an email that the lockdown was necessary to limit community transmission in “order to keep schools open, safeguard health system capacity, and protect the province’s most vulnerable populations.”
“In partnership with the chief medical officer of health and our local medical officers of health, we continue to closely monitor the evolving situation to advise if and when public health measures need to be adjusted,” said a spokesperson for the ministry.
A U.S. Centers for Disease Control and Prevention study from September found that adults confirmed to have COVID-19 were approximately twice as likely to have reported dining at a restaurant in the two weeks before they became ill compared to those who tested negative.
Another U.S. study, which appeared this month in the British science journal Nature and which the Ontario science advisory table drew upon, suggests a link between where people go and patterns of infection.
The study used anonymized cellular data to track the movement of 98 million people in big American cities from neighbourhoods to hundreds of thousands of what they called “points of interest,” which included restaurants, grocery stores and churches, from March to May.
Researchers ran a simulation to predict, based on visits, where residents were becoming infected and found that a small fraction of points of interest accounted for a large percentage of infections. The results of the simulation produced infection rates that were close to what was happening in the cities at the time.
Those points were typically places that “tend to have denser visitors and the visitors tend to stay longer,” such as restaurants, said Emma Pierson, who co-authored the study while working on her PhD at Stanford University. Pierson has a master’s degree in statistics from the University of Oxford, where she was a Rhodes Scholar, and is now a senior researcher at Microsoft.
Density was also key to why the model predicted higher infection rates in neighbourhoods with fewer white people, which is consistent with what actually happened during the first wave, said Pierson.
The model showed people from these neighbourhoods were not able to reduce their mobility as much, in part because they were more likely to be essential workers.
Loading...
Loading...Loading...Loading...Loading...Loading...
“It’s hard for them to work from home,” Pierson said.
The places they went to typically had more visitors and were “therefore more dangerous,” said Pierson, noting that in the U.S. there is a correlation between higher population density and lower socio-economic areas.
Although the study in Nature didn’t assess whether individual restaurants were riskier than other points of interest, a simulation to reopen each sector by category, while keeping the others closed, showed reopening restaurants would lead to hundreds of thousands of infections in the Chicago area.
Reopening full-service restaurants was particularly risky, according to the study, with researchers predicting roughly 600,000 additional infections in the Chicago area by the end of May, more than triple the next category of establishment.
Pierson said part of the reason may be simply the number of restaurants.
Across the metro areas used in the study, full-service restaurants, together with gyms, hotels, cafés, religious organizations and limited-service restaurants, produced the largest predicted increases in infections when reopened.
Statistics from the Nature study used by Ontario’s science advisory table show that additional COVID-19 infections associated with the reopening of venues (after a lockdown, for example) are much higher for the bottom 10 per cent of income earners than for the top 10 per cent.
The risk of being infected in restaurants, places of worship and grocery stores was disproportionately large for the lowest 10 per cent of earners.
“These are the essential workers. That’s not the people who buy their organic bananas. That’s the people who work there who get infected,” said Juni. “This is like the perfect storm for transmission. They are exposed because they are essential workers.”
More research in the U.S. could lead to understanding how retail and restaurants can more safely reopen in a pandemic.
The study in Nature found that if points of interest in Chicago capped maximum occupancy at 20 per cent, it would cut new infections by more than 80 per cent while reducing overall visits by only 40 per cent.
“If you reduce maximum occupancy, it can potentially enable you to reopen more efficiently because it creates a large reduction in infections for a relatively small reduction in visits,” said Pierson. “The reason for this is it only affects places when they’re most crowded and most dangerous.”
The authors also believe the results of the study show that reopening has a disparate impact on at-risk neighbourhoods, risk that could be mitigated through stringent occupancy caps, distributing food to areas with high-risk stores, more testing and improved paid leave or income supports for essential workers, as well as personal protective equipment.
Toronto has had a higher incidence of the disease in the northeast and northwest parts of the city.
Juni said he is hopeful that the science advisory table will find ways to make restaurants and other venues safer.
“Basically, try to wear a mask as often as you can, try to ventilate as well as you can in these places,” he said. “Keep the tables apart from each other so at least groups of people don’t interact with each other. These will all be helpful in the future.”
“The problem is that only if you restrict relatively strongly (will) you get this thing under control because it’s so contagious.”
https://news.google.com/__i/rss/rd/articles/CBMihAFodHRwczovL3d3dy50aGVzdGFyLmNvbS9uZXdzL2d0YS8yMDIwLzExLzI4L3doZXJlLWFyZS1wZW9wbGUtY2F0Y2hpbmctY292aWQtMTktY29tbXVuaXR5LXRyYW5zbWlzc2lvbi1zdGlsbC1hLXB1enpsZS1pbi1vbnRhcmlvLmh0bWzSAQA?oc=5
2020-11-28 12:00:54Z
52781211522242
Tidak ada komentar:
Posting Komentar