‘Case for social distancing is extremely strong’
Experts urge aggressive action as preventive
The virus behind what is now officially a worldwide pandemic can spread before it causes symptoms and for as many as 12 days after a person recovers, according to new research that is raising questions over whether health officials in Canada should be taking aggressive steps now to limit human contact.
The World Health Organization has formally declared the eruption of COVID-19 a pandemic, weeks after experts said the world was clearly in the early stages of one. In declaring the first pandemic since the outbreak of H1N1 in 2009, the global health agency’s leader, director-general Tedros Adhanom Ghebreyesu, said he is “deeply concerned by both the alarming spread and severity, and by the alarming levels of inaction.” As of Wednesday, there were more than 118,000 cases of COVID-19 in 114 countries, and the virus continues to spread.
The developments have some asking, is it time to pull the fire alarm?
“There is so much unknown,” said Pierre-gerlier Forest, director of the University of Calgary’s School of Public Policy. “People could be asymptomatic and contagious. This is the big difference from SARS.” With SARS, people were sick, then contagious.
The ultimate goal is to reduce the number of people a single infected person will infect, to less than one. “If you can bring it under one, the epidemic starts to dwindle,” Forest said. “The question is how to do it,” and do it early, rather than late.
Since the consensus suggests that people can be contagious and asymptomatic, making it difficult to know who is spreading the disease,
“the case for social distancing is extremely strong,” Forest said.
University of Toronto physician epidemiologist Dr. David Fisman said this week that his team’s model for Canada, without public health intervention, had an overall attack rate of 70 per cent, but that falls sharply, by about half, if we add modest public health control, meaning finding and isolating around 50 per cent of mild cases through testing.
The attack rate would drop significantly further with aggressive social distancing — sporting events played behind closed doors, people working from home, video conferencing, no concerts, no mass gatherings, shopping off peak hours and closing all schools. “It’s time,” Fisman said Wednesday. “You can do it now or do it in three weeks when the ICUS are starting to fill.”
Although there have been relatively few reported cases in children, it’s also likely that children are minimally symptomatic, but excellent spreaders. “Countries that have done this successfully have closed schools,” Fisman said. “We can figure out whether it’s overkill later.”
Aggressive social distancing is about “flattening the curve,” slowing the number of new infections and the spread of a virus that has rattled the stock market.
“We need measures that, while painful for all, will slow social contact,” Harvard University infectious disease epidemiologist and microbiologist Marc Lipsitch tweeted this week. “And we need to stop feeling sheepish about it and just realize that some places (Italy, Iran) are in crisis and some are very likely in the days before a crisis that will be less bad if we slow down the virus to reduce peak demand on health care.
“We will not intervene as intensely as China, making speed more important,” Lipsitch said.
He and others believe the number of new cases being reported daily are only “newly discovered” and that the true number of cases is much larger because most never get tested, and we’re undercounting mild cases. Some research suggests people can shed infectious tissues early on, sometimes even before they develop symptoms. In fact, a new study is providing the strongest evidence yet that “pre-symptomatic transmission is occurring.”
The analysis involved 135 confirmed cases of COVID-19 in Tianjin, China, and 93 cases in Singapore. Canadian and international researchers looked at the incubation period — the time between exposure and getting symptoms; and serial interval — the time between someone getting symptoms, and someone they infect getting symptoms.
The researchers looked at two very detailed transmission clusters and they found “that people can start infecting others three days before they start seeing symptoms themselves,” said Dr. Caroline Colijn, a professor and Canada 150 Research Chair in mathematics for evolution, infection and public health at Simon Fraser University. “One of the huge roles of these social distancing, self-isolation and quarantine measures is to try to stop those transmissions that could be happening even before people feel sick,” she said.
“This is still low risk in Canada right now,” Colijn said. “But I think it really underlies those preventive measures we can take.”
According to the federal pandemic plan, any imposed restrictions on individual freedoms must be proportional to the magnitude of threat. “This principle of ‘least restrictive means’ should always be a consideration when enacting social distancing measures,” the plan reads.
But when should Canada take more aggressive measures? From the infectious disease angle, “the answer is, soon,” Colijn said. “But I don’t know the cost implications of that. It has to be weighed in.”