Antibody tests could shine light on 'stealth virus' that causes COVID-19, including early cases, experts say

A newly approved blood test could answer a question on many Manitobans' minds — was that knock-down, drag-out flu they recently had actually COVID-19?

It probably wasn't, scientists say. But it's not clear who will get to find out — or when.

"The overall testing strategy is still being determined," a provincial spokesperson says.

On May 12, Health Canada announced it has approved the first COVID-19 serological test for use in the country to detect antibodies specific to the virus.

The hope is that the LIASON test can be used in Canadian laboratories to help develop a better understanding of whether people who have been infected are immune to the virus.

Over the next two years, Manitoba will take part in the federal random testing effort. It's not yet been determined who will participate, when the tests will be available or if they'll be available upon request.

The green light comes after several antibody tests that had previously emerged on the market did not pass the "reliability test," scientists say.

"You have to make sure that the antibody is actually showing that the person had COVID before, and not, say, another coronavirus," says Dr. Sumon Chakrabarti, an infectious diseases specialist with Ontario's Trillium Health Collective. "It's the 'gold standard' of testing."

Morden, Man., resident Shauna Martens decided early in the pandemic that if given the chance, she'd have the antibody test.

"Yes, I would," she says. "And maybe my kids, too."

That's because in December 2019, Morden experienced a spike of tenacious viruses. At one point, close to 500 school-aged children in the small city were sick. Parents, like Martens, also became ill.

And in January 2020, Morden resident Joanne Ens, 24, died six days after getting flu-like symptoms, and developing secondary infections as a result.

Then came the pandemic.

That got Martens thinking about that curious December illness.

In May, the World Health Organization revealed it was reassessing the timeline of the coronavirus's spread. The health agency now questions whether the virus had actually emerged weeks earlier than originally thought — as early as the end of 2019.

That got Martens doing the math.

"I was like, 'Ah, well, maybe we already had it. Maybe that's what we had,'" she said.

Now she and dozens of others who have since reached out to CBC question whether their own winter viruses were actually early cases of COVID-19.

Chakrabarti understands their curiosity.

"There were probably cases before," he said. "It's just they were undetected."

Still, he adds, once the antibody test is made available, most Manitobans will likely learn they weren't early COVID-19 survivors.

"I bet you a lot of those people who were very sick in December had influenza or another one of the viruses," he says. "There's a bunch of them that circulate during the wintertime."

That's just one of the factors that created the "perfect storm of circumstances" for COVID-19 to flourish, says Dr. Ciriaco Piccirillo.

How could the family doctor diagnose COVID-19, when COVID-19 wasn't yet a thing — but influenza was?

Piccirillo, a senior scientist of infectious diseases and immunity at the Research Institute of the McGill University Health Centre, gives the scenario of someone going to their local clinic with symptoms like a headache, fever and a dry cough.

"What do you think the physician concluded back in February? It would have been, 'You probably have the flu. You should go home and have chicken soup.'"

What's worse, "I don't know how it is in Manitoba, but this year [in Quebec], the flu season was a rough one," he adds.

(For the record, Manitoba's was a busy one, too).

Then there's the devil in the details that scientists are now learning about COVID-19, he says. A person can be infected and contagious days before experiencing the first symptoms. In some cases, they may never develop symptoms.

"So you have a virus that is infecting us [that] stays under the radar," Piccirillo ​​​​​​said. "And as a result, as people go on with their daily lives and their normal daily activities, they're continuing to propagate infections."

Stealth virus

The antibody test could flash a bright light on this "stealth virus," Chakrabarti says.

The test examines a patient's blood work to see what antibodies (a type of protein, Chakrabarti explains) a person has in their system. 

Those antibodies latch onto certain viruses — or bacteria — and help "take them out of circulation and help your body clear it," Chakrabarti said.

"So if you have an antibody to, for example, COVID-19, it means that you may have immunity."

The antibody test will help scientists get a better understanding of the newest coronavirus "cousin on the block," Dr. Ciccirillo says — in part, by giving them a better picture of whom in the past had exposure, and therefore who could be at risk in the future.

"I don't think this one is the black sheep of the [coronavirus] family," he said. "But the fact that we have never been exposed to it [means] our systems are basically playing catch-up."