A study out of Britain has found that after a five-day quarantine, about a third of people infected with COVID-19 were still contagious.
PCR tests detect virus particles but cannot tell whether they are infectious or merely inactive remnants.
Lorna Harries, the lead author of the study at the University of Exeter Medical School in England, says at five days, 30 per cent of people still exhibited clinically relevant levels of potentially active virus.
Researchers said that after a 10-day quarantine, one in 10 people might still be infectious, and some people retained these levels for up to 68 days.
Last month, the Ontario government shortened isolation times for those with symptoms who are fully vaccinated.
The isolation period was reduced for those who are fully vaccinated, and children under 12 years old, from 10 days to five days following the onset of symptoms.
“These individuals can end isolation after five days if their symptoms are improving for at least 24 hours, and all public health and safety measures, such as masking and physical distancing, are following,” the government said in a statement at the time.
But people who are unvaccinated or are immunocompromised are required to isolate for the previous recommendation of 10 days.