Hitching a ride: How risky is carpooling during COVID-19 pandemic?

Whether it's giving your neighbour a ride to the grocery store, or letting a friend borrow your car, health experts generally advise against sharing a vehicle during the COVID-19 pandemic.

But like many coronavirus-related scenarios, determining the probability of infection from carpooling isn't so clear cut.

A lot can depend on who is in the vehicle, how large it is, and whether or not you're introducing extra risk factors by making other stops.

"If the person you're driving works in an office with one other person versus somebody who works at a meat processing facility, the risk in that car is going to be dramatically different," said Craig Jenne, a microbiologist and infectious disease researcher at the University of Calgary. "If you stop to get takeout food, well now you've increased the risk in the car as well.

"So it's little things we don't think about that actually have a huge potential to influence risk and outcomes."

With some provinces having introduced bubble systems for socializing between two households, Jenne says having a friend you're already interacting with in your car is "no different from having them in your kitchen" — except that you can't stay two metres apart in a car.

"So if it's somebody who's not part of your normal cohort than I think we have to take (that) into consideration," he said.

Zahid Butt, an infectious disease expert and professor at the University of Waterloo in Ontario, says it's best to be cautious, regardless of the scenario.

If the person doesn't live with you, you probably shouldn't drive around with them.

"Most of the cases that we're seeing now are asymptomatic, so you don't know whether they have the virus," Butt said. "If a person is sitting in the car next to you, there is a chance (of spreading it)."

Butt and Jenne both say the duration of the trip doesn't necessarily matter, though the longer you spend with an infected person the more likely your chances of contracting the virus.

An infected person that sneezes in your direction within minutes of the trip could also result in transmission rather quickly.

Allocating the passenger to the back seat also won't help much if the distance between the people in the vehicle is still less than two metres.

That rule applies whether it's a small compact car or a large SVU.

"The further away somebody is the less (is the) likelihood that something can be transmitted in the air, but that's by far not a foolproof safeguard," Jenne said. "You can't simply say if you sit in the back row, you're far enough away."

Jenne says face masks, when worn by both the driver and the passenger, can minimize risk if you do decide to travel in a car with others.

But homemade masks won't protect people "100 per cent" from contracting COVID-19, Butt says.

Other types of vehicle-sharing bring different risks.

Borrowing a car from a friend can be dangerous, for example, but experts say risk diminishes once you disinfect high-touch surfaces like the steering wheel, gear shift, radio knobs and door handles.

Time will also deactivate the virus, so allowing days between switching drivers reduces the chances of picking up the infection from the car.

As for taxis and ride-sharing services, Butt says it's probably best to avoid those during the pandemic. There are safety precautions you can take if you do have to use them though — like not touching you face while in the car and sanitizing or washing your hands when you get out.

"There might be other persons who were sitting there, and you don't know how regularly they sanitize the car," Butt said. "So you just have to be careful."

Maintaining a physical distance is still the best approach, the experts say.

That means taking public transit with a bunch of strangers — provided there's enough room to spread out — might be safer than riding in a car with one friend.

With most public transit systems not operating at full capacity, Butt and Jenne say its more likely to keep a safe distance on a bus or subway now than in a private vehicle.

But again, there are other factors to keep in mind.

"In a car, there's less people, so if the one person you're with does not have the virus, you're good to go," Jenne said "If you're on a bus with 10 people and one has the virus, your risk went up. But you can also maintain better distancing on a bus than in the passenger seat of a car.

"So the equation is quite complicated than car versus bus and more versus less."

This report by The Canadian Press was first published May 29, 2020.