Ebola is a viral disease that has been a threat for more than a decade. Detected in Africa, this virus causes a serious haemorrhagic fever and has high fatality rates. There have been indications that it is from bats that these viruses infect humans, and a new study in Bangladesh lends this further credence.
Source of the Disease
Diseases like Ebola emerge periodically in human populations, and just as suddenly, disappear following an outbreak. This patterns owes itself to the virus being ‘zoonotic’—a virus that infects humans via another organism. Zoonotic diseases are hard to eradicate because we can’t immunize animals in the wild. This is why we have effective vaccines for Measles (not zoonotic), but Ebola or the flu is always on the radar for health officials. Thus, a crucial step in studying zoonotic diseases is determining their primary hosts. One criterion for primary hosts is that the virus shouldn’t be too harmful to them. If it were, it would kill the host organism and would not be able to circulate for long periods of time, as it does. Humans are definitely not its primary hosts—each outbreak subsides soon after its origin because it is so lethal.
Ebola Virus in Bats
The organism which is the original reservoir of Ebola virus has not been known for certain, though previous studies have found a few species of bats infected with Ebola. Now, researchers have studied 276 bats in three regions of Bangladesh and identified antibodies against the Ebola virus in 4% of these, meaning that the bats have, at some point, been exposed to the Ebola virus. However, they haven’t found live virus in bats, which is the piece of evidence necessary to confirm that bats are a reservoir, i.e. a permanent ‘store’ of the virus.
What Does this Study Tell Us?
Bats harbouring antibodies for Ebola has already been found—what new information does this study yield? This study tested bats for 2 strains of the virus: the Reston strain which has been seen in animals across the world (and has not caused human disease), and the more deadly Zaire strain, which has a whopping mortality rate of around 80% and was previously seen only in Africa. Antibodies for both these strains were found by this study, which means that a Zaire Ebola infectious outbreak in Asia remains a distinct possibility. How possible? We don’t know, until we have more evidence on prevalence of the virus in its primary hosts.
This research was conducted by the EcoHealth Alliance. You can read about this study here.