Reality Check: How People Catch Ebola, And How They Don’t (Very Good Interview)
It’s confusing. You hear that Ebola victim Thomas Eric Duncan was so contagious that two Dallas nurses in protective gear caught the virus. But then you hear, in more recent days, that apparently nobody else did, including the inner circle who lived with him and cared for him. The CDC announced today that all of Mr. Duncan’s “community contacts” have completed their 21-day monitoring period without developing Ebola.
How to understand that? And how to address alarmists’ claims that for the nurses and so many West Africans to have caught Ebola, it must have gone “airborne”?
I turned to Dr. Elke Muhlberger, an Ebola expert long intimate with the virus — through more than 20 years of Ebola research that included two pregnancies. (I must say I find this the ultimate antidote for the fear generated by the nurses’ infections: A researcher so confident in the power of taking the right precautions that she had no fear — and rightly so, it turned out — for her babies-to-be.)
Dr. Muhlberger is an associate professor of micriobiology at Boston University and director of the Biomolecule Production Core at the National Emerging Infectious Diseases Laboratories (widely referred to as the NEIDL, pronounced “needle”) at Boston University. Our conversation, lightly edited:
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Ebola is transmitted by having very close contact to infected patients. So we know that it is transmitted by bodily fluids, which include blood, first of all — because the amount of virus in the blood is very, very high, especially at late stages of infection — but it’s also spread by vomit, by sputum, by feces, by urine and by other bodily fluids.
The reason for that is that at late stages of infection, the Ebola virus affects almost all our organs — it causes a systemic infection. One main organ targeted by Ebola virus is the liver, and that could be one of the reasons that we see these very high concentrations of viral particles in the blood. But I would like to emphasize that that occurs late in infection.
Early infection is the other way around. The primary targets — the first cells that come in contact with Ebola virus and get infected — are cells that are part of our immune system. And these cells most likely spread the virus throughout our body. But there are not so many cells infected at the very beginning of the infection, which might be the reason why Ebola virus patients do not spread virus at the very beginning of infection. And that’s why it’s safe to have contact with these patients, because the viral titers in their blood are so low that we cannot even detect them with methods like PCR, which is one of the methods we use to diagnose Ebola virus.
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...from experience, we know that this virus is not transmitted early in infection. If the viral titers are very low, if you’re not able to detect free viruses in the blood, then it seems Ebola virus is not transmitted to other people. Which is very good because, theoretically, that makes it really easy to control Ebola virus infection. And the reason why we have such a disaster right now, with almost 10,000 infected in West Africa and more than 4,000 already dead, is not so much the transmissibility of Ebola but rather the lack of infrastructure in these countries.
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When someone is infected with measles and then sneezes or coughs, and is not sick at this point, they can transmit the virus to others and you’re not even aware that someone with the disease is contacting you. That’s the big difference with Ebola virus and these bigger droplets — but nevertheless droplets, of course. When Ebola virus patients start to transmit the virus, they have already developed a fever and are obviously sick.
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And that’s exactly what we know about Ebola virus: You really need close contact, especially contact with those who are severely ill, and that is because of of this special mode of transmission. Even early in infection it is not so contagious. Those who are at risk to get infected are those who take care of the ill patients — health care workers or relatives at home — and then the second group who got really hard hit by Ebola virus infections is those who care for the deceased, like relatives who washed the deceased, which is not really our funeral rites. So that is not a real risk for us, especially if you know someone died of Ebola virus.
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I think we really should focus on the outbreak in Africa. To make it crystal clear, we do not have an Ebola virus outbreak in the U.S. We do have an Ebola virus outbreak in West Africa. We have to do all we can do to stop this outbreak for our own good because we do not want to have a similar situation as the Dallas patient.
I also want to make clear that this virus is not transmitted by the air, and this virus will not be transmitted by the air. In virology, we are not aware of a single virus which changed its transmission route so dramatically. I’ve asked a lot of my colleagues: Are you aware of any virus which changed its transmission route? Any virus which went from blood-borne or transmitted by bodily fluids to airborne? And nobody knew of any virus.
http://commonhealth.wbur.org/2014/10/reality-check-how-catch-ebola
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