Medical Director of Specialised Infectious Disease unit at the Emory University Hospital in Atlanta, Dr.Bruce Ribner has stated that, in general, patients who have recovered from Ebola virus infection have developed a very robust immunity to the virus.
Ribner who led the team that cared for the two American aid workers, Kent Brantly and Nancy Writebol, who were released after being pronounced “recovered” from Ebola contracted Ebola while working in west Africa, told Scientific American that Ebola survivors develop antibodies against the virus and they also develop cell-mediated immunity.
“In general, the finding is it’s basically like being immunised-it would be unusual to get infection with the same strain. We are still evaluating that in our two patients.
Cross-protection is not quite as robust. There are five strains of Ebola viruses. Even though that data is not great, the feeling is there is potential for being infected if you go to a different part of Africa and get exposed to a different strain.
Ribner said the two survivors would be followed as outpatients, and as part of evaluation. “They have agreed to undergo additional testing so we can better understand immunity to Ebola virus. We are meeting with them periodically.
“What we found in general is that among our Ebola patients, because of the amount of fluid they lost through diarrhoea and vomiting, they had a lot of electrolyte abnormalities. And so replacing that with standard fluids without monitoring will not do a very good job of replacing things like sodium and potassium. In both of our patients we found those levels to be very low.
“One of the messages we will be sending back to our colleagues is even if you don’t have the equipment to measure these levels, do be aware this is occurring when patients are having a lot of body fluid loss.” Immunity: “We are still evaluating that in our two patients. Cross-protection is not quite as robust. There are five strains of Ebola viruses. Even though that data is not great, the feeling is there is potential for being infected if you go to a different part of Africa and get exposed to a different strain.
“We are going to be following those two patients as outpatients, and as part of our evaluation they have agreed to undergo additional testing so we can better understand immunity to Ebola virus. We are meeting with them periodically.
“We are not being critical of our colleagues in West Africa. They suffer from a terrible lack of infrastructure and the sort of testing that everyone in our society takes for granted, such as the ability to do a complete blood count—measuring your red blood cells, your white blood cells and your platelets—which is done as part of any standard checkup here.
“The facility in Liberia where our two patients were didn’t even have this simple thing, which everyone assumes is done as part of your annual physical.
“Our two patients also gained an enormous amount of fluid in their tissues, what we call edema. In Ebola virus disease there is damage to the liver and the liver no longer makes sufficient amount of protein; the proteins in the blood are very low and there is an enormous amount of fluid leakage out into the tissues. So one of the takeaway messages is to pay closer attention to that and perhaps early on try to replace some of these proteins that patients’ livers lack.
Evaluation: Looking at Ebola survivors who were discharged and successfully resolved the infection, following up several months later and evaluating their family members, there has never been any evidence that family members became infected. A lot of the thinking now is this probably was not live and is not important in terms of control of infection. We did give both of our patients the standard recommendations, which are contained on the CDC [U.S. Centers for Disease Control] Web site—not having unprotected sex for three months. Among the handful of patients that received the experimental drug ZMapp, some have died. Considering the mortality rate for the current Ebola strain is almost 50 percent what can we say about ZMapp?
Experimental drugs: Experimental drugs are experimental drugs because we don’t know if they will work. That is true both with the preparations patients received in Liberia and other preparations that are being considered for treating patients with this infectious disease. We are a long way from being able to say that someone that received one of these agents benefited, it had no impact or it may be that their outcome may be impeded. Until we have good studies looking at outcomes of patients who received these medications, compared to patients who didn’t receive them, we should be very cautious.
Hysteria: I would go further to say that there is a fair amount of almost hysteria and people feeling they must have these preparations to survive. In the past people thought they needed agents for treatment, and the agents actually turned out to impair people’s ability to survive. The focus should remain on aggressive intensive care and the ability to correct abnormalities metabolically, rather than receiving any magic vaccine or product that may or may not improve survival.