Screening people at airports for signs of a new coronavirus isn’t likely to detect too many cases, health experts say.
As governments around the world work to contain the spread of a new coronavirus, which likely originating in Wuhan, China, one of the measures they’re taking is to screen passengers going through airports.
In Canada, travellers arriving in Vancouver, Toronto and Montreal are being advised to notify border officers if they’re feeling sick. A question at customs kiosks also asks whether they’re experiencing respiratory symptoms.
If a person has symptoms, they may be questioned by a quarantine officer, who could order them to report for a medical examination.
If the passenger is not showing symptoms, but has been to Wuhan or other affected areas, they may be provided with information on who to contact if they begin to get sick.
In some countries, officials are scanning people’s temperatures for signs of fever.
Screening measures might not be doing much to spot cases though, said Dr. Allison McGeer, an infectious disease specialist at Toronto’s Sinai Health System, who contracted SARS while fighting the outbreak in 2003.
“The best evidence is that in any of the circumstances that people have either tested or done with modelling … they make very little difference,” she said.
“If you ask me, is there scientific evidence that says it works? Absolutely not.”
A study of Canadian airport screening measures during the SARS outbreak found that while hundreds of thousands of passengers were screened, and some were referred for follow-up checks, officials didn’t spot a single case of SARS.
Partly, this is because of the sheer number of travellers and how quickly people can get around the world, the authors wrote.
“Given the relatively short travel time, detecting persons at the border who are incubating any of the known infectious disease pathogens is unlikely,” they wrote.
“The absence of symptoms or signs of infection and a corresponding lack of specific, extremely rapid, easy-to-use diagnostic tests make border detection of infectious diseases unlikely.”
Preliminary estimates by a team from the London School of Hygiene & Tropical Medicine, released this week, suggested that thermal scanning would identify fewer than one in five passengers infected with the coronavirus.
There’s a simple reason, the authors said: you’d have to actually have a fever while you’re in the airport.
Many people might not show symptoms until several days after they’re infected. Officials said Friday that Canada’s fourth case of coronavirus, a woman in London, Ont., didn’t have any symptoms while she was on the plane.
“Fever screening doesn’t work because lots of people come during the incubation period,” McGeer said.
“And when you have a fever, you don’t have a fever for 24 hours. You have fever intermittently.”
Some people with chronic conditions have a constantly elevated body temperature, too, she said.
“There are a lot of limitations to doing temperature screening,” said Jason Kindrachuk, an assistant professor and Canada Research Chair in emerging viruses at the University of Manitoba.
One other potential problem is that staff have to be adequately trained to properly take a temperature with an infrared thermometer.
“Is that person trained well enough to know that you have to be at a certain distance to get an accurate reading? Because if you’re a bit too far, you’re not necessarily reading that person’s temperature, you’re reading air temperature,” Kindrachuk said.
Kindrachuk is also concerned that temperature screening might provide a false sense of security, and even discourage people from going to the doctor if they start feeling sick, because they already passed one screening.
Asking people to report their symptoms also relies a lot on trust, he said.
“The trust factor is where I think a lot of people are concerned. Are people just going to lie or try to hide symptoms so that they can get through security?”
Some cases will always slip through, he said, but flight records and other travel data can help to identify travellers who might need more screening.
McGeer thinks that Canada’s current screening measures are striking an appropriate balance, reassuring the public that the government is vigilant while not spending too much time on things that haven’t been shown to work.
“I think they’re being totally reasonable,” she said.
“There’s no perfect answer to this. You have to kind of work with the circumstances and the logistics.”
Harsher measures, like travel bans or closing borders, have economic and other consequences, she said.
“You say, ‘Well that’s just money.’ Right. But it’s not just mone, it’s jobs.”
Taking someone’s livelihood away can have terrible consequences for their life, she said.
The World Health Organization, meanwhile, is not currently recommending travel restrictions.
“Evidence has shown that restricting the movement of people and goods during public health emergencies may be ineffective and may divert resources from other interventions,” it said in a statement earlier this week.
Kindrachuk thinks that if the outbreak gets worse — particularly if we start seeing more person-to-person transmission outside China — Canadian officials might want to suggest that travellers from affected regions voluntarily quarantine themselves when they get home.
McGeer believes that public health authorities need to learn to better manage the public’s anxiety about new diseases.
“We’re in real danger now of the fear taking over and of doing things that will do substantial amounts of harm without benefit,” she said.