Is heat needed to clean reusable masks? Your COVID questions answered

We're answering your questions about the pandemic. Send yours to COVID@cbc.ca, and we'll answer as many as we can. We publish a selection of answers online and also put some questions to the experts during The National and on CBC News Network. So far, we've received more than 53,000 emails from all corners of the country.

With more of us wearing reusable, non-medical masks, CBC readers have had some good questions about how to keep them clean.

Also, some of you are wondering how to get to a testing centre safely if you don't own a car, whether you can get COVID-19 twice, and whether infrared thermometers are dangerous. Here are the answers.

Is heat or soap more important for cleaning reusable masks?

Health Canada recommends cleaning masks in a washing machine using a hot cycle and then drying them completely.

Colin Furness, a professor at the University of Toronto's Dalla Lana School of Public Health, notes that, in fact, viruses can't reproduce outside the body and don't survive well on fabrics, so cleaning reusable masks is mainly to get rid of potentially smelly bacteria. For that, he said, heat works better.

There are some simple ways to hand clean your mask with heat. Dr. Anand Kumar, associate professor of medical microbiology at the University of Manitoba, suggests one of the following:

• Steaming for 10 to 15 minutes.

• Heating at 70 C for one hour.

• Immersing in boiling water for 30 seconds.

However, he notes that from the perspective of killing coronaviruses, even washing in cold water should be fine, as long as you use detergent or soap, which damages the capsule of coronaviruses.

WATCH | How to safely wear and clean a mask

Are damp masks less effective?

That depends on what they're made of, experts say. The protection offered by masks comes mostly from the physical barrier created by the fibres in the fabric.

"Most damp masks shouldn't be less effective," said Kumar.

However, he said the filtration abilities of N95 masks may degrade when they go beyond damp to "out-and-out wet."

Furness said in some fabrics, fibres could potentially cling together when damp, leaving larger gaps.

On the other hand, some fibres might swell up when damp and may make the mask more effective, he suggested. But that might also make it harder to breathe through.

Regardless, in general, public health officials recommend changing masks when they become damp or dirty.

Kumar notes that damp masks allow bacteria to grow, although most of the time that results in them becoming smelly "but not really dangerous by and large (within reasonable limits)."

WATCH | Washing tips for reusable masks

What's the safest way of getting to a testing centre if I don't have a car?

Many car-free readers, including a number of seniors, have written to us wondering this.

Diane Fairfield, 77, of Vancouver, B.C., recently completed a two-week quarantine after being exposed to someone who tested positive for COVID-19. She was asked by provincial health officials to go to a COVID-19 testing site. "I have no way to get there," she said.

She was advised to take a taxi, but called the taxi company to make sure that was okay. She found it disconcerting when they told her it wasn't a problem, and they regularly transported airport travellers returning from high-risk COVID-19 hotspots.

To help people without cars, Sudbury, Ont., sent paramedics to do COVID testing house calls, something Fairfield herself suggested be done in Vancouver. Kitchener, Ont., offered free rides to testing centres in old ambulances.

But in most communities, those options don't exist. So what to do?

According to Dr. Matthew Cheng, an infectious disease doctor at McGill University Health Centre, "the safest thing would ideally be to walk."

However, if that's not possible, it's okay to take a taxi, get a ride from a friend, or take public transit, he said.

If a friend is offering a ride, he recommends making sure that person follows public health guidelines, so as not to expose yourself to more risk. A ride from that kind of friend may be safer than a taxi or Uber driver, who is potentially exposed to many people a day.

In any case, he recommends that to reduce risk during the ride:

• Wear a mask.

• Clean your hands.

• Keep the windows open.

WATCH | What to expect in a taxi or ride-hailing service

Can you get COVID twice?

There are still knowledge gaps when it comes to understanding our immune response to the virus that causes COVID-19, including how well, and for how long, someone who has recovered from the disease is protected from reinfection.

"In most cases you would expect those antibodies to provide you with protection for a period of time," said Dr. Michael Ryan, the World Health Organization's head of emergencies. But we don't yet know how lasting that protection is against the virus that causes COVID-19.

Researchers are now considering at least four confirmed cases of COVID reinfections that were reported in late August — including one in Hong Kong, two in Europe, and one in Reno, Nevada.

In most of these cases, the patients contracted a different strain of the virus and their reinfection symptoms appeared to be relatively mild. However, doctors said the Nevada patient developed more severe COVID-19 symptoms the second time around.

Reinfection "may represent a rare event," the Nevada researchers wrote. But, they said, the findings implied that initial exposure to the virus may not result in full immunity for everyone who has been infected by it.

In other research, one small study on COVID-19 immunity found that people who were asymptomatic or mildly symptomatic had their antibodies diminish within two to three months. Though larger studies are needed, the findings also cast doubt on whether "herd immunity" will ever be achieved with COVID-19, where enough of the population is protected that the virus it has nowhere else to spread. You can learn more about that study in this video.

Can infrared thermometers used for COVID screening damage your pineal gland?

You've probably seen no-contact, gun-shaped thermometers being pointed at people's foreheads to screen for COVID-19-related fevers at locations ranging from supermarkets to airports to daycare centres. We've had at least one worried reader write to CBC News asking, "Is having an infrared thermometer pointed at your forehead dangerous to your brain ... specifically the pineal gland?"

The answer is no.

Infrared thermometers work by focusing the heat — infrared light — emitted from your skin onto a sensor. So your body is actually beaming infrared rays into the thermometer and not the other way around.

"The infrared devices don't actually emit anything," said Dr. Lynora Saxinger, an associate professor of medicine at the University of Alberta in an email.

There is sometimes a laser that helps focus the beam, but it needs to meet the same safety regulations as lasers in other consumer products such as toys and laser pointers.

As for the pineal gland, which produces hormones such as melatonin, it's not even anywhere near your forehead, Dr. Haris Sair, director of neuroradiology at Johns Hopkins University noted in an interview with the Associated Press: "This thing is smack dab right in the middle of the head."

If you're still nervous about getting the thermometer pointed at your forehead, it will actually work on other parts of your body. In fact, a recent study posted as a preprint (not yet peer-reviewed) found that pointing the thermometer at the wrist instead of the forehead gave a more stable measurement and both forehead and wrist measurements had great fever-screening abilities.