When did the virus start to circulate in Quebec?

Thousands of samples collected in Quebec weeks before the COVID-19 epidemic begins to rage will be tested to see if the SARS-CoV-2 virus was already circulating in the population in late 2019 and early 2020.

This research project will be launched this summer by the Quebec Public Health Laboratory (LSPQ), thanks to specimens collected last fall and at the start of winter as part of the regular influenza surveillance program. This program, piloted for 15 years by the National Institute of Public Health of Quebec (INSPQ), will allow researchers to access frozen samples from thousands of patients who have consulted for flu-like symptoms in dozens of medical groups family (GMF) and clinics across Quebec since October 2019.

“Thanks to these samples taken before the pandemic, we will be able to search for the virus and find out if individuals were infected as early as December or early January before the first cases are declared,” said Tuesday at Duty the Dr Hugues Charest, head of the molecular biology sector at the LSPQ.

Almost 1,500 samples will be screened to try to clarify an issue that has puzzled many scientists since research in other countries has demonstrated the presence of cases of COVID prior to the official date of the start of the pandemic.

In France, research was able to detect a case of COVID as early as December 27 – and we suspect even another to have been diagnosed on November 16 – one month before the first three official cases confirmed by test in France January 24. In the United States, researchers estimate that the virus circulated as of November or December in New York, although a first case was confirmed only on January 21 in the State of Washington. Experts in genomic analysis of strains of the virus in China have estimated that SARS-CoV-2 may have appeared in humans as early as the end of August.

In Quebec, a first case was officially confirmed on February 28, that of a Montrealer returning from Iran, who arrived on a flight from Qatar.

But according to the Dr Charest, SARS-CoV-2 infections may have passed under the radar in December and January in hospitals and clinics where patients have consulted for flu-like symptoms. While Quebec was not yet on “alert”, infected travelers could have returned from their destination where COVID was already circulating.

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According to the Dr Gaston de Serres, epidemiologist at the INSPQ, these samples collected to monitor influenza are very precious. “Of course we are likely to find cases, even if it is likely to be very few,” he believes.

However, the fact that only a portion of the 1,500 samples collected across Quebec come from the metropolis, where the epidemic hit first and the strongest, however, reduces the possibility of finding several early cases. These samples also immediately exclude patients with other typical symptoms of COVID, including anosmia, headache or diarrhea, who could have consulted in the clinic, adds Dr From Serres.

“For 15 years, this surveillance network has been invaluable in monitoring influenza and verifying the effectiveness of the flu vaccine. It is also used to monitor the emergence of other viruses. A few years ago, it became known that an enterovirus causing paralysis in children was also present in adults, without them having any symptoms, “explains Dr From Serres.

A thousand other samples collected in four hospitals in the province in Trois-Rivières, Quebec, Rimouski and Chicoutimi, from patients hospitalized for complications associated with influenza will also be included in this “prepandemia” screening project. The ministry has also asked that the detection of SARS-CoV-2 be integrated next year into this ad hoc respiratory virus surveillance program in hospitals, explains Dr Rodica Gilca, medical consultant at the INSPQ.

British Columbia, with a sentinel network of doctors, has already started this process and will have completed in a few weeks the testing of samples dating back to November 2019, said the Dre Danuta Skowronski, surveillance officer for influenza and emerging respiratory pathogens at the BC Center for Disease Control. “But we don’t expect to find many cases because the prevalence has been very low here.”

According to the Dr Charest, of the LSPQ, the lull that the laboratories used to detect COVID are beginning to know will allow this research project to start at the end of the summer.

“The teams, mobilized since the start of the pandemic, are tired. This (this project) was not a priority. But there, the number of tests to analyze decreases every day. This research will help us to better understand what happened in Quebec, perhaps even to discover certain peculiarities of the virus that we still elude, “he says.

This research is in addition to that already started by other Quebec researchers associated with Genome Canada, to complete the genomic sequencing of samples from 50,000 patients declared positive for COVID since February 28. This work should ultimately allow us to learn more about the strains circulating in Quebec, their contagiousness and provide tools to choose the most appropriate vaccine to protect the population.

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