Ebola Outbreaks Sparked by Survivors Show Virus’s Long Reach
Treatment advances helped many more survive the disease, but may have seeded fresh flare-ups
JOHANNESBURG—Two ongoing Ebola outbreaks in Africa appear to have been sparked by survivors of earlier epidemics, according to research that is drawing attention to how long the virus can lurk in parts of the human body, only to reappear months, or even years, after the initial illness.
The findings are based on tests of virus samples taken last month from flare-ups of the disease at the sites of the two largest Ebola epidemics in history: Guinea and the eastern Democratic Republic of Congo. Those epidemics—including the one that killed more than 11,000 people across West Africa between 2013 and 2016—hastened the development of Ebola vaccines and therapies that have since offered hope of turning around the fight against one of the world’s deadliest viruses.
Now, researchers are trying to understand whether those lifesaving scientific advances have planted the seeds of fresh transmissions of the hemorrhagic fever.
Doctors have known for some time that Ebola can lie dormant in areas shielded from the body’s immune response—such as the eyes, brain and a man’s testes—for months after a person has cleared the initial infection. In 2016, scientists documented how a Guinean man, who recovered from Ebola in November 2014, had passed on the virus to a sexual partner some 15 months later.
But many were puzzled when research published this month found that a spate of new Ebola cases detected in February in the same part of Guinea were caused by a version of the virus that was remarkably similar to the one at the center of the 2013-2016 epidemic. The most likely explanation for the limited number of mutations found in the virus, the researchers concluded, was that this new outbreak was again triggered by a survivor of that epidemic—rather than a fresh instance of Ebola jumping from animals to humans.
“When we received the results we were surprised,” said Abdoulaye Touré, director general of Guinea’s National Institute for Public Health and one of the scientists behind the research. “We didn’t know that one could have a suspected transmission from a survivor five years or more later.”
Health authorities in Guinea haven’t been able to connect the first case in the latest outbreak—a nurse who passed the virus on to several mourners who attended her funeral—to a survivor of the earlier epidemic. “We are still investigating,” said Dr. Touré.
That link was easier to establish earlier in February, when genomic sequencing showed that a woman in eastern Congo had died of the same virus that infected her husband in September 2019, during an outbreak that lasted nearly two years and killed more than 2,000 people. What was startling, however, was that the husband’s semen had repeatedly tested negative for traces of Ebola virus—most recently on Jan. 29.
Why the virus festers in some people long after they have tested negative, and under what circumstances it can become infectious again, is poorly understood 45 years after Ebola was first identified. That is partly because until the 2013-2016 epidemic there were few survivors to observe the long-term effects. The virus has historically killed as many as 90% of those infected.
“Earlier outbreaks were a lot smaller and with very few survivors,” said David Heymann, professor of infectious disease and epidemiology at The London School of Hygiene & Tropical Medicine who heads a World Health Organization advisory group that is examining the recent Ebola resurgence in Congo. “We are learning a lot more about them.”
More than 17,000 people survived the epidemic that swept from Guinea into Liberia and Sierra Leone. Many of them continue to suffer from debilitating headaches, fatigue and other body pains, although it is unclear whether these symptoms are due to injuries caused by the original illness or are related to lingering infections.
One theory that experts are examining is whether antibody therapies that have shown to reduce the mortality rate from Ebola to about one-third for those who receive them may somehow push the virus into hiding. Such therapies can’t eliminate the virus from places that are hard to reach for the immune system, said Eric Delaporte, a professor of infectious and tropical diseases at the University of Montpellier in France.
Those drugs—known as monoclonal antibody treatments and similar to the antibody cocktails used against Covid-19—were widely administered in the earlier outbreak in eastern Congo, including on the husband of the woman who died last month. Their use was much more limited, however, during the West Africa epidemic.
The most obvious response to a growing threat from survivors would be a broader rollout of Ebola vaccines, which so far have mostly been given to contacts and contacts of contacts of those infected, as well as healthcare workers deployed near outbreaks. But the current Congo outbreak is also adding more questions over how long immunity from those shots lasts, since the woman who died had been vaccinated in September 2019, three days after her husband tested positive.
Experts from the WHO and other agencies are now investigating whether her immunity had lapsed, whether the shot the woman received had somehow been spoiled or whether she was among the unlucky few for whom the vaccine didn’t trigger a sufficient immune response.
The good news is that the current outbreaks in Guinea, where nine out of 18 people infected have died, and Congo, where 12 cases and six deaths were recorded, appear close to being contained. The last Congolese patient tested positive for a second time on March 21, triggering a 42-day countdown to declare the outbreak over. Guinea hasn’t registered a new patient since March 4.
“Saving lives is a good thing,” said Prof. Heymann. “Now we need to innovate [new responses] if by saving these lives we have made some people long-term carriers of this virus.”