What’s keeping scientists from vanquishing Ebola?

In the 25 years since my book The Hot Zone traced the emergence of extremely lethal viruses, one of them has proved to be the most destructive: Ebola. At this writing, Ebola has killed hundreds in the Democratic Republic of the Congo, in the second largest outbreak since the virus was identified in 1976. The largest—from 2014 to 2016 in three West African nations—resulted in almost 30,000 cases, nearly half of them fatal. Fierce international efforts helped quell Ebola that time, but there are no assurances that the virus (above) has ended its assaults on the human species. Ebola is hard to arrest for many complicated reasons (below). But scientists keep trying—and what they learn will equip us to face this virus, and possibly worse, in the future.

Why is Ebola so hard to fight?

1. The vaccine’s requirements
Ebola vaccine has to be kept cold. But in tropical areas where little refrigeration is available, the vaccine can quickly become useless. And we don’t yet have a dried or otherwise nonperishable form of the vaccine.

2. Constraints and costs of new drugs
There are experimental, genetically engineered drugs for Ebola, but it’s not yet clear if they’ll be broadly effective, and affordable enough that they’ll be feasible for mass treatment of Ebola victims.

3. The failure of a technique that stopped past viruses
In 1966, during a large outbreak of smallpox virus, vaccinators tried a technique called ring vaccination with great success: They vaccinated people in a ring around the infected person. This trapped the virus inside a wall of immune people and stopped it from spreading. But attempts to use the technique with Ebola have run into problems. Ring vaccination requires a stable government or other authority maintaining civil order. The areas with Ebola outbreaks in the Democratic Republic of the Congo are controlled by violent militias that won’t let vaccinators do their work.

4. Gaps in scientists’ understanding of how Ebola kills
Ebola remains mysterious. It is unbelievably aggressive in the human body, but scientists still don’t understand all the virus’s mechanisms. The great military strategist Sun Tzu said, “Know the enemy.” We’re still getting to know Ebola. When we finally do, we’ll know the paths to defeat it.