The first time Liberia was declared free of Ebola in May 2015,  people celebrated in the streets. Now, all of West Africa is free of  Ebola, but the virus may come back yet again, WHO warns.

The first time Liberia was declared free of Ebola in May 2015, people celebrated in the streets. Now, all of West Africa is free of Ebola, but the virus may come back yet again, WHO warns.

EPA/Ahmed Jallanzo

WHO declares Ebola outbreak over

The World Health Organization (WHO) today declared Liberia free of Ebola, marking the end of the outbreak in West Africa. “Today is a good day,” Rick Brennan, director of emergency risk management and humanitarian action at WHO, said at a press conference in Geneva, Switzerland. But he also urged continued vigilance, warning that there was a significant risk of flare-ups. “While this is an important milestone and an important step forward, we have to say that the job is still not done. That’s because there is still ongoing risk of re-emergence of the disease because of persistence of the virus in a proportion of survivors,” Brennan said.

The announcement came 42 days after the last confirmed Ebola patient in Liberia twice tested negative for the virus. It is the first time that all known chains of transmission in the three Ebola-ravaged countries have been stopped. Sierra Leone was declared free of Ebola on 7 November 2015, and Guinea followed at the end of December 2015. All three countries are now in a 90-day period of heightened surveillance.

The outbreak in West Africa was by far the largest Ebola on record and the only one to have become a full-fledged epidemic. More than 28,500 people were sickened by the virus, and 11,315 died since the outbreak began in a remote Guinean village in December 2013. At the height of the epidemic there were hundreds of infections every day, and patients died in front of overfilled treatment centers that had shut their doors. “Detecting and breaking every chain of transmission has been a monumental achievement,” Margaret Chan, director-general of WHO, said in a press statement.

While this is an important milestone and an important step forward, we have to say that the job is still not done.

Rick Brennan, WHO

Because Ebola can persist in some tissues and bodily fluids of survivors for months, there is still a risk of the virus re-emerging. This is what happened in November 2015 in Liberia, after the country had been declared free of Ebola for the second time. There have been 10 such flare-ups that were not part of the original outbreak, Brennan said. “And we are expecting more.” The risk of such a re-emergence decreases over time, however, as more and more survivors clear the virus from their body. Scientists are most worried about Ebola’s persistence in the semen of survivors where it has been shown to be present for up to a year.

As scientists and doctors move to discuss what they have learned from the deadliest Ebola outbreak on record, the virus’s uncanny ability to stick around in survivors is just one of many outstanding questions. Another is how to do better research during such emergencies. “The research activities during the outbreak yielded very little,” says Stephan Becker, a virologist at the University of Marburg in Germany. “We need to be prepared before such an outbreak starts.” Armand Sprecher of Doctors Without Borders in Brussels says African countries at risk for the next outbreak in particular need to strengthen their scientific and ethical review boards that evaluate and approve proposals. “I think it is doable, but it will require work, and I am not sure who will work on this,” Sprecher says.

Much of the discussion has also focused on the role of WHO, which was heavily criticized for how it handled the outbreak, particularly in the beginning. There have been several reports recommending reforms, but even if those changes are implemented that may not be enough, Sprecher says. “WHO is not set up as a meritocracy, and unless the envisaged overhaul changes their governance structure, I am not sure that shuffling the cards and expanding their budget will make them into an organization that will be less disappointing next time.”

But the most important lesson is the need to strengthen health care systems in low- and middle-income countries, says Anthony Fauci, who heads the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland. “If there was a system to have recognized and stopped the outbreak that began with the child in Guinea in December 2013, we might have avoided the explosive outbreaks in Sierra Leone and Liberia.”

*Related content: "Ebola's Thin harvest"—a special package examining the clinical research done during the Ebola epidemic.

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