N.S. native leads genetic-analysis research
Genetic scientists are shining a light on exactly how fast and how far the coronavirus that causes COVID-19 can spread.
For a study recently released in the journal Science, researchers used genetic sequencing to analyze particular specimens of the
SARS-COV2 virus.
“As the virus naturally replicates, it has little mistakes in its sequence that are mutations but they’re not the bad kind of mutations that make the virus any more dangerous,” said Bronwyn Macinnis, a Nova Scotia native and director of pathogen genomic surveillance in the Broad Institute’s infectious disease and microbiome program in Boston, who led the study.
“They just give it a little fingerprint that we can follow and how the virus is moving across time and space.”
FROM ONE TO 300,000
For example, the researchers looked at a “superspreading” event linked to an international technology conference attended by about 170 people in Boston in the last week of February.
One of the participants unknowingly brought the virus into the conference and it quickly spread. Initially it was thought about 100 people were infected “but we went on to sequence the cases from the conference, or a subset of them,” said Macinnis, who was born in Lower Sackville and did her undergraduate work at Acadia and Dalhousie universities.
“What we saw was that the viruses from the conference had a particular fingerprint that we were able to track farther and more broadly than those 100 cases that happened at the event."
By the middle of May, they estimated that 20,000 cases in the Boston area were associated with the conference. The team was able to pinpoint cases across the city including among its homeless population.
The conference-linked virus quickly broke out into other states such as Florida as infected people travelled out of the Boston area. Macinnis's team estimated that by May 1, a mind-boggling 300,000 cases in the United States could be traced back to that one infected person at the conference.
NURSING HOME OUTBREAK
Her team also looked at a deadly nursing home outbreak in early April. The
residents and staff were screened for COVID-19 prior to a planned relocation of residents. Even though none were identified as symptomatic at the time of the screening, it was determined that 85 per cent of the 97 residents and 40 per cent of 97 staff were infected.
“This all happened over the course of a few days,” she said. “Ultimately many people became sick and several people died but it was just one of those just incredible examples of how quickly the virus can spread through vulnerable populations.”
Genomic analysis determined three quite different variations of the SARS-COV2 virus were introduced into the nursing home but only one could be linked to virtually all of the infections.
POWERFUL TOOL
The genetic analysis of viruses isn't new — Macinnis has worked in the field for 10 years — and she noted that in Canada, the Canadian COVID-19 Genomics Network was established in April for large-scale SARS-COV-2 sequencing.
But this recent research confirms genomics can be a powerful tool in understanding exactly how viruses can spread.
“if you had 85 per cent of all your residents in a care home being infected, you might think COVID came into the facility many times but that wasn't the case (in Boston), it was just a small handful, just one introduction that did all the damage,” Macinnis said.
“It's scary but it's really helpful information to know. (We must) make sure we continue to be vigilant because any introduction in the wrong circumstances can have a devastating effect.”