“We need to buy time for a vaccine against the coronavirus"

Marcel Salathé during his coronavirus lecture on 26 February 2020. Credit: Alain Herzog, EPFL

Marcel Salathé during his coronavirus lecture on 26 February 2020. Credit: Alain Herzog, EPFL

After his extensive lecture on the current coronavirus outbreak, we asked EPFL Professor Marcel Salathé, an expert in digital epidemiology, a few follow-up questions.

Q: What makes COVID-19 and its propagation so unique?

COVID-19 — or rather the underlying virus, SARS-CoV-2 — has nothing unique about its propagation per se. It is a respiratory virus that does what viruses do, i.e. to propagate itself from host to host. Unfortunately, it seems to be rather good at doing that in the human population, and seems to be spreading even more effectively than the influenza virus which causes the flu. It is also unfortunately ­­­- to the best of our current knowledge - more deadly than the seasonal flu. But unlike the flu, the people who are most at risk from critical complications, or even death, are the elderly. A pandemic, i.e. non-seasonal flu, often affects young adults more strongly.

Q. What makes it so hard to contain and/or treat, compared to seasonal flu?

To be clear — we are not good at all at containing the flu. Every year, it infects about 10% of the human population, and that with vaccines. For COVID, we don’t even have a vaccine (yet). Vaccines are still our number one weapon in our fight against the flu — without the vaccine, the flu would infect probably around a third of the population, which is what we normally see for pandemic, non-seasonal flu. Also, because we are exposed to the seasonal flu each year, over time everyone has some form of immunity against some variants, either through vaccines or through infections. To this novel coronavirus, it currently looks like there is no or very little immunity in humans.

Q. What are some things institutions like EPFL can do to prevent the spread of the virus?

As you may know, EPFL and other public institutions have been publicly criticized recently by the head of the communicable disease division at the federal office for public health, for taking "excessive measures” - for example with the schools’ policy that people returning from China should not come to the campus for 14 days. The criticism was that this doesn’t follow the official federal line. I must say I was quite stunned to hear this. I think that EPFL is doing the right thing, for the good of its community, even if the measures so decided are more intense than what the federal office recommends at a given time point.

Q. What is the best strategy for containing and treating COVID-19?

There are currently no particular COVID treatments. Hospitals will treat patients to the best of their knowledge, depending on the severity of the disease. For containment, we have the options of various so-called non-pharmaceutical interventions, ranging from small but important personal measures such as frequent and thorough hand-washing, not shaking hands etc. to more drastic community measures such as cancelling large events, traveling restrictions, and the like. The former is something everyone can start to do. The latter is of course more serious, and should be recommended only after careful deliberation.

Q. How do you think the outbreak will evolve globally?

I think there is currently little hope that it can still be contained, and we must plan for global spread. I will be very happy to be wrong about this but from looking at the data, and talking to many of my epidemiology colleagues, I can see very little diverging opinions about that. Our goal now has to be to focus on mitigation, i.e. making sure we can dampen the impact, and delay the epidemic as much as possible, in order to buy us time for the potential development of a vaccine, or drugs, and to make sure the healthcare systems won’t be dramatically overburdened.

Q. Which countries are at higher risk?

Hard to say. In general, countries with better healthcare infrastructure, better surveillance, and more transparent governance are generally in a better situation than others.

Q. How can we know when the pandemic has reached the tipping point?

If you mean the peak, then that’s something that will show up in the numbers.

Q. Why is closing the borders considered inefficient?

Because it runs under the assumption that infections come from abroad. The first ones always do (by definition that’s correct in all countries but one) but it takes only a few infections inside the country to seed local outbreaks. Open borders also bring a lot of essential goods and services to the country, and any risk-benefit analysis would strongly be against closed borders. And once you have local spread, closing borders makes no sense because you already have the problem at home. These kinds of questions have been modeled extensively and we understand well that their effect is very limited.

Q. What is the role of digital epidemiology in the COVID-19 outbreak?

Digital in general is a massive asset in fighting infectious disease. The rapid data sharing, enabled by digitization, is itself enabling more rapid drug and vaccine development. We can also use digital data streams such as Twitter to better understand the concerns, discussions, worries, and questions in the population. In order to effectively fight a pandemic, you have to bring the population along — you can’t just do things top-down only. That world is long gone. It seems to me that not everyone has fully understood that yet.