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‘It’s just not easy to catch:’ Dissecting the dangers of contracting Ebola

October 25, 2014 at 5:46 PM EDT
As health officials work to reassure the public about the Ebola scare in the U.S., Dr. Stephen Morse of the Mailman School of Public Health at Columbia University joins Hari Sreenivasan in the studio to discuss in detail when the virus is actually dangerous.

HARI SREENIVASAN: You’ve heard assurances from public health officials the last several weeks about the Ebola scare.

Tonight, we want to go into much greater detail about when the disease is dangerous and when it’s not.

For more, we are joined by Dr. Stephen Morse. He is a professor of epidemiology at the Mailman School of Public Health at Columbia University here in New York.

First, let me I guess start with the news from yesterday when the two governors said they were going to take these increased measures of quarantining medical workers who come back from these countries. Will this work or is this more of a systematic response to the fear that people have?

DR. STEPHEN MORSE, COLUMBIA UNIVERSITY: I think largely it’s something that looks good and will make us feel better, but I think it is largely a response to the fear. After all, these health care workers, although they may be the most likely to be infected because of their close contact with the patients, are also the ones who are most likely to be responsible to take their temperature and be careful.

HARI SREENIVASAN: So, you know, there’s this line in the sand about symptomatic versus asymptomatic. People are contagious when they’re systematic. How do we know Ebola is not contagious before the victim starts showing symptoms?

DR. STEPHEN MORSE: Well, everything we know about Ebola is based on the experience of 24 epidemics from 1976 on. The virus, I don’t think, has changed that significantly. And generally, these don’t change that much. So, what we do know from past experience is it requires direct contact with infected bodily fluids of the patient, or sometimes in the case of those who succumb, the corpse, the skin can also be infectious.

So, if they’re not bleeding or vomiting or doing any of those other things, there are no infected liquids to come in contact with, the likelihood is very great that they’re not going to be able to infect anyone until they show symptoms.

HARI SREENIVASAN: So, one of the concerns has been how viruses have mutated in past. Is there any discussion of the possibility that this virus could mutate into something that’s not just transmitted from bodily fluids but something that could be transmitted by air or any other way?

DR. STEPHEN MORSE: Well, all of these viruses mutate. HIV does, influenza does, and, Ebola, of course, has been studied recently and a number of mutations have been shown but we don’t have any example ever of any virus that whatever mutations it’s undergone has changed in its route of transmission. HIV has had many opportunities to do that, and it still hasn’t really fundamentally changed in that respect.

With Ebola, it may not be so much mutation or the amount of mutation but, you know, just simply the experience we have with it suggests that it’s not going to change that much.

HARI SREENIVASAN: OK, I’d like to discuss a couple of scenarios that New Yorkers here were very concerned about and perhaps extract from that something the rest of the country could learn. So, if this individual for example, this doctor was standing a foot away on a subway car or if I had taken the taxi after he used it, what are the chances of getting it if he was showing symptoms versus if he was not?

DR. STEPHEN MORSE: If there were symptoms and if, for example, he had left some blood behind or vomited or something like that, then there might be some risk, especially if one happened to touch it, or touch it to their eyes or nose. But in most cases, there is very little risk. And if there are no symptoms, there wouldn’t be any of this material to leave behind. And there’s not that much virus in sweat during the early stages.

So, I think it would be very unlikely, in fact almost impossible, for someone to get infected by an asymptomatic patient, one who has not yet shown symptoms of disease.

HARI SREENIVASAN: one of the concerns here for example is if he touched a specific bowl ball and somebody else touched it, right? I mean, again, it has to be blood or vomit or something else?

DR. STEPHEN MORSE: Yes, in general. And in general, they have to have had symptoms already.

And we have a number of examples that I think bear this out. One of the most severely ill patients, Patrick Sawyer, flew from Monrovia, sick as could be, he was so sick he could barely get on the plane, to Lagos, Nigeria, where he thought he had to go to a meeting and insisted on going. And the Nigerian government actually did contact tracing and found all the ones they could of the other passengers on the plane. I think they found 56 other passengers, and not a single one had become infected.

So, it’s– unless you’re really getting very close, like the health care workers who are taking care of the patients, it’s just not that easy to catch.

SREENIVASAN: So, there was a lot of concern in New York when initially that first night we heard this patient had a 103 temperature, and then it was clarified that it was 100.3.

What’s the temperature that we should be concerned about?

DR. STEPHEN MORSE: Well, this depends, of course, what your normal body temperature is because some people may have a little bit low, or a little bit high from the textbook. But 103 — he is certainly, as in the Duncan case, 103 would be certainly something I would be very concerned about; 100.3 I think is still something to consider, given his circumstances, he probably knew that this was something significant. Ordinarily, you might think you were coming down with a cold or the flu or something like that. But if you have been in contact with Ebola-infected patients you might have a lower threshold for being concerned and doing something.

HARI SREENIVASAN: All right. Dr. Stephen Morse from the Mailman School of Health at Columbia University — thanks so much.