Asymptomatic carriers under the spotlight
Montreal cases top 20,000
MONTREAL — There are probably thousands of Montrealers who are unknowingly spreading the novel coronavirus but showing no symptoms, two local experts said Wednesday.
As the virus continues to rage out of control in the city, the role of asymptomatic carriers has come into focus, as well as the importance of ramping up the number of tests for the virus.
“From what we’ve seen in the small number of studies done around the world, somewhere between a quarter and a third of the general population has it, but doesn’t know they have it,” said Ketra Schmitt, an associate professor at the Gina Cody School of Engineering, who studies how viruses are spread.
Christopher Labos, a cardiologist and a science writer for the Montreal Gazette, said there is a lack of comprehensive testing around the world, so the virus probably spread silently in many other urban centres even before its outbreak in Montreal. He blames an earlier spring break as part of the reason that Montreal has been more severely affected than other urban centres in Canada.
“We probably imported a lot of cases from overseas, so we had more cases, to begin with,” he said. “And remember this virus doubles in number of cases very quickly. The virus was probably circulating in the U.S. a lot earlier than people realized because they weren’t doing a lot of testing there. Quebec had a lot of snowbirds and a lot of people travelling from Florida.
“The most logical explanation is that a lot of the cases were imported from travellers, and that led to community transmission in the province, because of the reality of how the virus spreads.”
Labos said he is surprised by how people infected by the virus can show very mild symptoms or none at all, while others are so severely affected.
He said one trend that seems universal is that the virus spreads more rapidly in areas where there is a higher density of population. That’s why Montreal has been severely affected, but also why the denser parts of the city have seen the most reported cases.
The public health department Wednesday reported an increase of 354 cases of the virus from Tuesday, for a total of 20,232 people who have been diagnosed with COVID19 on the island of Montreal. The number of deaths rose by 60 in one day to 2,063. On Montreal Island, one in 10 people confirmed to have COVID-19 have died.