COVID: How do I know if I have been re-infected?

Reinfection with COVID-19 due to the rise of highly contagious Omicron mutants More and more common..

According to public data, 10% of Canadians recently infected with the Omicron BA.2 variant had previously been infected with COVID-19, according to Dr. Sakib Shahab, director of health care in Saskatchewan.

“It shows that once you get Omicron, it doesn’t mean you’re bulletproof now,” Shahab said earlier this month.

As a result, it is important to keep in mind what constitutes reinfection, said Dr. Dale Carina, an infectious disease doctor at Joseph Brant Hospital in Burlington, Ontario. According to Kalina, people infected with COVID-19 may continue to shed the virus for several months after the initial infection.

“You can certainly keep the virus flowing, and it’s not necessarily a marker of reinfection,” Karina told CTV News.ca in a telephone interview Tuesday. “This is one of the difficulties or pitfalls of PCR testing.”

This means that someone can continue to test positive using the polymerase chain reaction (PCR) test. Up to about 90 days After being infected with an existing residual virus, Karina said, even if the viral substance is inactive and the person is not necessarily contagious. This makes it difficult to determine whether the virus detected is due to a primary infection or a subsequent infection.

An increasingly used marker of reinfection instead is the progression of COVID-19 symptoms, said Dr. Lisa Barrett, an infectious disease specialist and professor at Dalhousie University in Halifax. She said that if a person infected with COVID-19 notices a clear improvement until the symptoms disappear and then the symptoms worsen again, this is likely a reinfection of COVID-19. ..

“The definition most people use is symptom resolution,” Barrett told CTV News.ca in a telephone interview Tuesday. “If possible, PCR or [rapid] A clear association between antigen testing and subsequent exposure and new infections due to symptoms.

“It is usually said that it takes more than 60 days to be considered a reinfection, but to be honest, this is an ongoing task.”

according to Ontario Public Health, Reinfection is considered a subsequent infection of SARS-CoV-2 that occurred at least 90 days after the initial infection. The Quebec National Institute of Public Health With a similar definition, SARS-CoV-2 reinfection is expected to occur at least 90 days after the onset of symptoms from the primary infection.

According to the Public Health Agency of Canada (PHAC), PCR test results may remain positive or fluctuate. Weeks or months Positive results obtained within 3 months of the previous infection after they were first performed may not actually represent a true reinfection. However, it is not yet clear how quickly reinfection will occur after the diagnosis of COVID-19, PHAC says.

On the other hand, the results displayed using the Rapid Antigen Test (RAT) are not expected to remain positive as long as the PCR test is done, Barrett said. This is because it targets specific proteins on the surface of the virus, not the genetic material of the virus. According to PHAC Ideal frequency of repeat tests The use of RAT has not yet been decided.

Despite some of the challenges associated with detecting COVID-19 reinfection by PCR testing, Kalina says that the ability to detect positive levels of virus samples is useful. When using the PCR test, a positive reading is generated via a fluorescent signal. The fluorescent signal is measured to determine the threshold for the cycle. This corresponds to the number of cycles required for the signal to exceed the amount normally found in the test sample.

As the cycle threshold increases, this means less target nucleic acid is detected in the sample and vice versa. Therefore, if the cycle threshold is high, it is possible that the genetic material of the virus is due to an old infection. If it is low, this indicates that the substance is associated with a more recent infection, Karina said.

Looking at this data in combination with symptoms helps physicians provide diagnosis and guide care. If someone re-infects COVID-19 and suspects that they have symptoms that are consistent with the virus, Kalina recommends that you consult your doctor.

“”[Part] One of the studies we do as a healthcare provider is to look at cycle thresholds and mix them with symptoms to put the whole story together, “says Kalina. “If possible, talk to your doctor …. It’s our job to help you navigate it.”

With a file from the Canadian Press.

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