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:
Is it really true you worked on Ebola through two pregnancies?
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Yes, but in the proper protective gear. That makes a huge difference, if you’re protected, if you know how to protect yourself, and that is the case in a Biosafety Level 4 lab, of course. If you compare the protective gear we’re wearing in a Biosafety Level 4 lab and the gear they’re wearing in West Africa now treating patients, it’s like comparing a stainless steel vault to a cardboard box.
But on the other hand, if you look at the nurses in Dallas, you say, ‘How did they get infected?’ It makes you worry that maybe protective gear isn’t good enough — but you’re proof of the opposite.
A Biosafety Level 4 lab is such a high-end lab, it is not possible to use protective gear like that in every hospital in the U.S.
Could you please lay out a brief primer on the biology of how Ebola is transmitted?
We know from previous outbreaks, and also from the current outbreak, that 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.
Is a virus only contagious when it reaches a certain level of “titer” or load? Continue reading