She Plots the Possible Arcs of the Pandemic

It has to be a bit awkward, really. If you work in the field of epidemiology this is your moment. It's show time. But one can hardly celebrate that fact. Never mind. SFU's Dr. Caroline Colijn doesn't have time for that anyway. “It's busy,” she says, before adding, “I'm not really at the front lines of this. I'm a mathematical modeller. I am focused more on getting leverage out of genomic data for pathogens. I just hope I can be useful.”

Make no mistake, Dr. Colijn is doing her part. She holds a Canada 150 Research Chair in Mathematics for Evolution, Infection and Public Health, and was among the lead researchers on a recent study on vaccines invented for disease prevention.

Her work connects epidemiology, genomics, evolution, math, statistics and probably in a pinch plumbing and small appliance repair. Certainly these days it involves fielding media enquiries multiplying more rapidly than pathogens.

Colijn's work informed a March 20 Globe and Mail article that examined several different scenarios based on more or less stringent responses. The inescapable takeaway of the study is that flattening the surging curve of infections requires drastic measures to keep people isolated from each other as much as possible. Anything less projected a grim death toll.

B.C. has implemented many of the more strict measures, including closing most places where people gather. If such restrictions stay in place, Colijn calculates, the infection rate is stretched over more time and peaks in the fall when the health system is better prepared.

Epidemiologists like Dr. Colijn are not lab-coated scientists staring intently at test tubes. Or at least, not just. “It takes all kinds,” she says. “We need people to isolate the virus, we need therapeutics, we need people thinking about vaccination, clinical trials, surveillance studies, monitoring health-care workers.”

And it takes mathematicians. “Mathematical modelling has been really well established since the days of John Snow and the first cholera outbreak,” Colijn says. (First on the list of historical John Snows, a clear number two on the Google search list.) “We are looking at who is at risk, why are they at risk, what's going on with this disease. It's a sub-field that tries to come to the rescue when we have a new emerging pandemic.”

“The role of mathematical modelling in infectious disease epidemiology is to think about the data we have at the population level, groups of people, links between the groups, rates of infection and case counts, and thinking about what that means for the dynamics of this thing going forward.”

Statistical models are always affected by variables. “We have a lot of hypotheticals,” she says. “We don't know what effect physical distancing is going to have. We hope to find that out next week. We don't know what therapeutics might be available, or when there might be a vaccine. We don't know about asymptomatic cases. We don't know about buildup of immunity in the population.”

And of course we don't know what will come out of the mouth of the president of the United States tomorrow. Already this week Trump has said, “I'd love to have it open and rarin' to go by Easter,” Is it possible to calculate a mathematical model that allows for President Stupidhead?

Dr. Colijn is philosophical. “If I despaired every time Donald Trump said something I thought was incorrect I wouldn't have a lot of time left over. We can factor it in insofar as, if irresponsible statements are made, it can undermine people's trust around distancing and they may do it somewhat less. I guess if you really wanted to monitor the impact of a particular statement you could monitor Twitter — for example if you thought Twitter sentiment was an indication of how well people were going to comply.”

(Interestingly enough Dr. Colijn's former employers, Imperial College London, did conduct a 2018 study of Twitter response to National Health Service messaging. But it said nothing about the effects of deranged tweet-happy knuckleheads.)

Colijn is even sympathetic to some of the other misguided chatter out there, such as people talking about the good old days of “chicken pox parties” where parents got kids together to pass the disease around and thereby gain immunity. “People aren't just being stupid,” she says. “We did have chicken pox parties. There was a reason for that. Chicken pox is not very lethal.”

“There have been suggestions that we should just let this virus take its course,” she says. “I think the fatality risk and the risk of overrunning our health-care system is too high, so it's not what I would advocate. But if you did it you would get to herd immunity faster. It's just a question of what price you are willing to pay. And it's not like chicken pox. We have a population that's not immune.”

This week Trump has begun saying the cure is worse than the disease. The lieutenant-governor of Texas says old people should sacrifice themselves for the good of the economy. “We're going to pay a big price with our economy anyway,” Colijn responds. “The question is how many deaths do you want to have while you do it?”

Colijn sees some hope but offers no easy reassurances. “I have seen a tremendous change in the patterns of contact between people. Hopefully we will stop seeing exponential rises and start seeing flattening [of the curve],” she says.

“The isolation measures we are doing right now go beyond what that [Globe and Mail] article assumed we would do. I hope we are doing enough to get the basic reproduction level below one. The problem is that we are not building up immunity while we do that. As soon as we go back to normal, if we have introduced cases [from other countries] or still have cases that we missed, then we start to see the spread again.”

So are we just delaying the onset of widespread infection? “I think that's a real possibility,” she admits.

But that's not necessarily a bad thing. “It could help if we delay until we have therapeutics, and until we are able to do app-based contact tracing and really comply with the results of that contact tracing. We will get better therapeutics, and a vaccine. But not in the next six weeks. That's not even a possibility.”

In the short term Colijn asks people not to despair. “If we don't see immediate decreases in the case counts that's OK. That's what we expect, because the cases we see reported today weren't infected today, they got infected some time ago. It takes time before symptoms develop and get into the reports. So don't lose heart if you don't see the effects of your social distancing playing out soon.”

“It's an unprecedented thing that we've been asked to do,” Colijn says.

Then it's time for her to go. “Got another call coming in,” she says. With misinformation flowing out at the speed of Twitter, the cleanup is a non-stop task.