Professor Yehuda Carmeli is head of the Department of Epidemiology at the Tel Aviv Sourasky Medical Center and a professor at the Sackler School of Medicine at Tel Aviv University. He is one of the medical professionals leading the Israeli Health Ministry’s response to the COVID-19 global pandemic.
Prof Yehuda Carmeli on how exactly the virus is transmitted, why it’s so contagious, whether Israel has the right strategy, how long we’ll be fighting it… and how many will die.
How many people will become infected worldwide if this pandemic is not checked?
There are various mathematical models that try to estimate the number of cases expected in different places. There is a saying about mathematical models that all of them are wrong but some are useful. We truly don’t know which of them is correct.
All models I have seen predict that by the end of this outbreak, which could be in several months or could be in a year or two, about 60-70 percent of the population will be infected at some point. Not all people who are infected become sick. Some don’t even notice that they have it, or have very minor symptoms.
But in the end you can take the world’s population and calculate 60 or 70 percent, and those are the numbers that will be affected by this pandemic.
When you hear figures like a 3 percent death rate, that’s just 3 percent of people who’ve taken a test and were confirmed to be infected, but the people who are being tested are not a random group, are they? Aren’t they more likely to get tested if they have symptoms?
Exactly, and probably the three percent [figure among those confirmed to have the virus] is too low… When you calculate the number of deaths, you are looking at patients some of whom did not yet have a chance to die; from the time of infection, fatalities take about two to three weeks.
If you look at the number of what we call closed cases, meaning cases of patients who either recovered or died, the numbers go to six to nine percent dead. But again, we don’t know six percent of what.
Can this disease be caught through the air?
I would say for all practical purposes, no. The answer is not actually yes or no. Under regular conditions, normal living conditions, it’s transmitted by droplets, which means that you get infected by droplets from someone who is one or two meters away from you.
Under very unusual conditions, for example, when a hospital patient is mechanically ventilated or having a specific procedure on the respiratory tract, you can have transmission by air.
Transmission by air is much more contagious and much more difficult to control. But I would say that for all practical purposes, in non-hospitalized patients, we can think about it as not being transmitted by air.
What makes this disease so contagious?
With previous events such as SARS-CoV-1, it was a virus that was less adapted to humans. When it caused disease it was severe, but it was not very easily transmissible from one person to another. It was mostly transmitted in hospitals, where you actually generated those airborne conditions.
The current coronavirus is much more transmissible between people and I don’t know the main reason for that. We usually measure transmissibility by the number of virus particles that are required to cause an infection. So I assume that the virus is at a higher concentration in those droplets. Or that it has a much easier way to attach to human cells and infect them.
Why are the elderly severely affected by COVID-19, but children don’t seem to be?
I don’t know. I don’t think that anyone knows. It’s quite unusual. There are other diseases where children are affected less severely than others. But here they’re almost not affected at all.
Do you think the measures that Israel is taking now are good? Are they an overreaction or an under-reaction? And how long will we be living like this?
In many ways this question goes beyond my expertise because from a purely medical epidemiological point of view, there should be a complete curfew on the entire country for maybe a month: Don’t allow anyone go in and out of their houses. And even within homes separate one person from another.
Well that’s impossible. So I think that what Israel is doing is a very good compromise.
I don’t think anyone at this point is trying to stop the outbreak. I think that’s probably beyond our ability already. What we are trying to do is slow the progression of the pandemic so the health care system can handle the situation.
I assume the restrictions will continue for several months.
It’s been 100 years since a similar event. The entire health care system will be completely preoccupied with dealing with this challenge that none of us has seen before.
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Full interview: Times of Israel
Header: Main image by NIAID Rocky Mountain Laboratories, shows a microscopy image of SARS-CoV-2. The spikes on the outer edge of the virus particles resemble a crown, giving the disease its name