The most terrifying aspect of Ebola may not be how it kills but how many. In the outbreak in West Africa that peaked in 2014, about half of people infected with the virus survived. Scientists have been mystified about what distinguishes the lucky ones from the less fortunate.
Now, for the first time, a study by the Centers for Disease Control and Prevention provides some clues about what may be going on in people’s bodies, and it turns out that those with severe disease experienced an out-of-control inflammatory response.
“Everybody who has looked at treatment in the past has looked at the virus. Our study says let’s look at the host – the hosts doing well and not doing well and see if we can alter the host response,” Anita McElroy a guest researcher in CDC’s Viral Special Pathogens Branch, said in an interview.
The study, which was published this week in the Clinical Infectious Disease Journal, is based on an in-depth look at seven patients treated at Emory University Hospital in Atlanta or the University of Nebraska Medical Center in Omaha. Emory treated some of the most prominent American victims of the outbreak, including physician Kent Brantly and nurse Amber Vinson.
It’s important to mention that the volunteers included in the research are distinct from the typical Ebola patient in West Africa in many ways, so it’s unclear to what extent the results hold true more broadly. These were all people who had grown up in developed countries, and most got the disease abroad and were repatriated by emergency air transport after they were infected. Many of them also received treatment with experimental serums, such as ZMapp. They also had access to early and supportive care by some of the best minds in the world, which most of the victims on the ground in Sierra Leone, Liberia and Guinea did not.
The other big difference is that everyone in the study lived through the infection. (A recent study in the New England Journal of Medicine showed the overall mortality rate for patients who were repatriated was 18.5 percent, which is much lower than the 50 percent for those treated on the other side of the world.)
Researchers tracked 54 different markers of immune-system activity from when the patients were admitted to the hospital to when they were discharged. They then categorized the patients into two groups – those with moderate disease and those with severe disease that was based on the kind of support they needed. Those with severe disease required ventilation and dialysis.
There were three important differences in those with severe disease. The first is a large inflammatory response, which appeared similar to people with autoimmune issues, such as rheumatoid arthritis and Crohn’s disease. That suggests that some of the therapies that work for these conditions may help with Ebola as well. They also found that those with severe disease had some dysfunction in their blood vessels and problems with blood clotting. Both of these are also issues for which we have known therapies.
Elroy, who is also a physician at Emory, emphasized that the study is very preliminary and that the therapies mentioned will have to be tested in animal models before they are given to humans – but that it gives us a direction to head in. Elroy said that while there are a number of therapies and medications that have come out of the recent Ebola outbreak, treatment is likely to require multiple approaches, and “an ideal therapy would target not just the virus, but augment the human immune response as well.”
“It appears there’s a sort of signature to moderate disease, and the question is how do we help those who don’t have those markers to get there,” she said.