Ebola study: Some people may be immune

AMcMasterresearcher is calling for a new, potentially life-saving study of the blood of people exposed to the Ebola virus,based on the idea that the deadly disease may also be safely immunizing scores of people.

Jonathan Dushoff, an associate professor of biology and an investigator with the Michael G. DeGroote Institute for Infectious Disease Research, is one of four researchers who published a letter in the latest edition of The Lancet medical journal calling for more blood tests to confirmthe idea that many Ebola infections are asymptomatic and how common that may be.

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That means people could be carrying the disease without experiencing any symptoms, and that in doing so they may have acquired immunity to the disease that could allow them to safely treat the sick.

"It might be that a lot of these hospitals already have a large subpopulation of immune healthcare workers, and they should be the ones on the front lines," Dushoff said, adding the same could be true within families.

And, if the scientists are right, the projected estimates ("The estimates right now are all over the place,"Dushoff said) of how many people will be sickened and die from the disease may be reduced, or at least refined.

Still, it remains unclear how many people have an asymptomatic Ebola infection. Its also unknown to what degree acquired immunity would protect them, if at all.

"Theres no guarantee," Dushoff said.

"We think its something thats worth trying and could help in the current outbreak depending on what the results are."

More blood needed

The scientists letter maintains a "forceful"public health response to Ebola is needed right now, but theyre hoping someone on the ground in West Africa will begin collecting more blood.

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Currently, the scientists idea is based on analyses of blood samples from people exposed to Ebola from animal reservoirs and earlier Ebola outbreaks. An analysis of one post-Ebola group of blood samples,evaluated specifically for antibodies, showed that 71per cent of seropositive individuals did not have the disease.

Its possible a percentage of those people have protective immunity against the disease.

Dushoff, who specializes in mathematical modeling, said its reasonably easy to see in peoples blood who has mounted an immune response to Ebola during an asymptomatic infection.

It gets complicated, he said, to know whether people are protected.

"We want to observe. We want to get blood from people on the frontlines now, because watching which one of those gets sick is going to help provide information about whos protected,"Dushoff said.

Figuring out who has an asymptomatic infection could be done in days, he said. Finding out who has acquired immunity takes longer, but may bepossible to know within weeks.

"The fact that theres an outbreak going on gives you a chance to figure out whether some people are protected."

The problem, he said, is that "you cant just watch people." Ebola is supposed to be fairly easy to prevent, so while it would be helpful for researchers to watch people they believe have acquired immunity, researchers also need to do everything possible to keep that person from contracting the disease.

Research community focused on emergency

Its not clear who would collect the blood samples to test this theory, butDushoff said hes "hopeful" that even though resources in Ebola-ravaged countries like Liberia someone will help outby collecting blood as part of an effort to protect people at risk.

One logical partner, the group points out in the Lancet letter, would be the groups studying the possibility of treating Ebola patients with blood transfusions from those who have survived the disease (a popular idea during the 1995 Ebola outbreak in the Democratic Republic of Congo.)

"The point of pushing the paper out now is that it could help very soon," Dushoff said, adding the global concern about Ebola has forced the research community to act.

"The fact that its happening so quickly made me push it to the top of my priority list," Dushoff said.

Journals, collaborators and other organizations have also begun working faster.

"People are treating Ebola as an emergency," he said.