How COVID-19 is transmitted and the symptoms it brings

As schools reopen, bringing more people in close regular contact with each other, and with more than 1,000 active COVID-19 cases in Alberta, the province's top doctor is reiterating to the public how the virus is transmitted.

As of Friday, Alberta's active COVID-19 case tally sat at 1,444. Meanwhile, three Alberta schools reported COVID-19 outbreaks as of Thursday and another three reported outbreaks on Sunday.

Public singing and limited band practices are now allowed by the province with health regulations like physical distancing still in place.

Dr. Deena Hinshaw, Alberta's chief medical officer of health, said on Friday she's heard many questions from the public about how COVID-19 is transmitted and why certain precautions to protect the public are in place.

"It's important we all understand how COVID-19 works," Hinshaw said.

Respiratory disease

A respiratory illness, COVID-19 can be spread when people breathe, cough or sneeze, releasing tiny droplets of liquid into the air. If those droplets come from someone who has COVID-19, the virus can be inside those droplets and make other people sick if they end up in other people's mouth, nose or eyes.

That's why Health Canada recommends people wear face masks and stay roughly two metres away from others when in public. When worn properly, even non-medical face masks can prevent infectious droplets from being spread to others, especially in crowded spaces where a two-metre distance from others isn't possible.

Face masks have become mandatory this summer in indoor public spaces in Edmonton and Calgary for this reason, as well.

The World Health Organization notes indirect contact, like contaminated objects and surfaces, can also spread COVID-19. People can become infected by touching these objects and then touching their mouth, nose or eyes. 

Frequently cleaning hands is also critical to stopping this spread.

14-day incubation period

Once the virus is inside your body, it can latch onto a cell inside your lungs. If enough of the virus latches onto and gets inside of the cells, they take over the cells and make copies of themselves.

But this takes time, Hinshaw said.

"Our immune system will be trying to fight the virus, and a lot of copies need to be made before reaching a tipping point where someone has enough virus to be able to infect others," Hinshaw said.

It takes five to eight days in most people for enough virus copies to be made that a person shows symptoms of the illness, Hinshaw said. But it can also happen sooner or take as long as 14 days.

This is why people arriving in Canada are asked to quarantine for two weeks, and why people who are exposed to COVID-19 as a close contact must self-isolate for 14 days, monitoring for symptoms. 

"It is entirely possible that they have the virus and it simply hasn't made enough copies of itself to be captured by that PCR test that shows up negative," Hinshaw said.

Anyone showing COVID-19 symptoms or who tests positive for COVID-19 must isolate for 10 days or until symptoms resolve, whichever takes longer.

People aren't infectious for a full 14 days, but Hinshaw said when these people get sick within that possible 14-day incubation can't be predicted.

Negative tests

When someone shows COVID-19 symptoms but tests negative for the disease, they only need to isolate until their symptoms are gone. If you're already showing symptoms, COVID-19 should show up in the test.

"You just need to stay home until you are well enough to not get others sick with whatever is causing the illness," Hinshaw said.

Health Canada notes that if you're tested too soon after COVID-19 exposure, there might not be enough virus in your body for an accurate result. So a test may come back negative even if you have the virus.

Experts say the chance of receiving one of these 'false negatives' drops as time goes by after being exposed to COVID-19, but a high rate of false negatives could mean many COVID cases aren't caught.

Symptom list

Hinshaw said on Friday that she's been asked why the province has such a long list of symptoms associated with COVID-19 and why kids with mild symptoms have to stay home from school.

It's because COVID-19 affects people differently, Hinshaw said, leading to a wide range of symptoms.

Some people can catch a fever from COVID-19 when their immune system tries to fight the virus, heating up the body's temperature. An inflammation occurs instead for other people when their bodies are fighting the virus.

"This is the reason that some people feel tired and achy, which is another symptom of COVID-19," Hinshaw said.

Shortness of breath or pneumonia can come from COVID-19 too as small air sacs in the lungs are inflamed and could fill with fluid.

This stops oxygen from reaching the blood and is why some severe COVID-19 cases require oxygen therapy or ventilators.

A runny nose, sore throat, nausea or diarrhea along with other symptoms can also be signs of COVID-19.

Even when someone has mild COVID-19 symptoms, a large number of copies can be made in their body, the disease can still be very infectious, and they might pass the disease on to someone who has a more severe reaction to it. People who aren't showing symptoms can also potentially spread COVID-19 as well.

"COVID-19 doesn't play favourites and none of us are immune. We can all spread it to each other, which is why we are all in this together," Hinshaw said.