Ebola’s Possible Future as an Endemic Disease

By Kari Lydersen | January 19, 2015 11:36 am

Last fall as the Ebola epidemic continued unabated, experts started discussing something that had never before been bandied about: the idea of Ebola becoming endemic in parts of West Africa. Endemic diseases, like malaria and Lassa fever in that region of Africa, are constant presences. Instead of surfacing periodically, as it always has before now, Ebola in an endemic form would persist in the human population, at low levels of transmission, indefinitely.

The debate was stoked by a paper written by the World Health Organization (WHO) Ebola Response Team and published in October in the New England Journal of Medicine. The sentence that grabbed the world’s attention was saved till near the very end: “For the medium term, at least, we must therefore face the possibility that EVD [Ebola virus] will become endemic among the human population of West Africa, a prospect that has never previously been contemplated.”

What would it mean exactly for Ebola to become endemic, and how would it change things?

Still Fighting

Christopher Dye, an author of the WHO paper, told Scientific American that, “To say it is endemic is, in one sense, to admit failure… Our goal, and our expectation, is that we will eliminate infection from the human population.”

Agencies in the U.S. agree. “CDC doesn’t believe that Ebola has reached a point of being endemic in West Africa,” said Dr. Jordan Tappero, Director of the Centers for Disease Control and Prevention (CDC) Division of Global Health Protection. The CDC does not officially designate diseases as endemic; in the U.S. that is typically done by state agencies. On the international level the classification is made by the WHO, which has not yet classified Ebola as endemic.

“The effort remains to get to zero cases of Ebola, and there are many efforts in place to accomplish that goal,” Tappero said. “We trust that sustained international support will result in an Ebola-free West Africa.”

But the truth is that with the current epidemic now having lasted over a year, the line is blurring between an ongoing outbreak and the “new normal.”

A Global Scourge?

The implications of an endemic Ebola are equally muddled. Epidemic risk management consultants Jody Lanard and Peter Sandman wrote on their website about one worst-case scenario: that visitors to the region will always be at risk of Ebola, which could result in “sparks” unpredictably landing in other countries and causing catastrophic economic and public health effects.

However other serious diseases, some of them more contagious than Ebola, have long been endemic in various developing countries. For example tuberculosis is endemic in major trade and tourism destinations including India, China and Brazil. But so far large-scale transmission to the U.S. has been avoided, even after drug-resistant cases of tuberculosis surfaced.

And Ebola’s high mortality rates of 60 to 90 percent could actually prevent it from becoming endemic. (Mortality in the current epidemic has been pegged at about 70 percent.) Ebola’s victims are likely to die quickly rather than spreading the virus for years, as happens with HIV, hepatitis C and other endemic infections.

Microbiologist Peter Piot, who co-discovered Ebola in then-Zaire in 1976, agrees. As he told the L.A. Times: “We (humans) are a very bad host from the virus’ point of view… A host that’s killed by a virus in a week or so is absolutely useless. So in all other outbreaks it eventually just disappeared from the human host and retreated into animals.”

If, on the other hand, the Ebola virus mutates so that it is less lethal, that could make it more likely to become endemic.

A Changed World

Whether Ebola is officially considered endemic or not, scientists working on the ground say that Ebola’s grip on West Africa has for the foreseeable future changed how they do their jobs.

Robert Garry, a Tulane University virologist who does frequent stints at the Kenema Government Hospital in Sierra Leone, said that even after this outbreak ends the hospital will likely continue to administer an Ebola test to any patient showing possible symptoms. Lassa fever, the more common viral hemorrhagic fever that Garry has been studying for years, has early symptoms basically identical to Ebola. Other common diseases like malaria, cholera and various parasitic infections can also present similar symptoms.

“Are we going to test simultaneously for Lassa and Ebola, or first for Lassa, then if it’s negative, for Ebola?” Garry said. “Those paradigms will evolve.”

Though they haven’t seen Ebola cases at the hospital in two months, Garry and his colleagues now wear protective Tyvec “bunny suits” with face masks and shields on a daily basis, and will likely continue to do so even after this Ebola epidemic is over. These suits aren’t as restrictive as the full protective gear worn by people treating Ebola, but they are much hotter and more cumbersome than the lab coats, gloves and eye protection that the Kenema hospital staff previously wore.

Hospitals might need to adapt in other ways as well. Wards to safely isolate and treat Ebola patients would need to be readily accessible. In a region where basic health infrastructure is already extremely strapped – with clinics often lacking antiseptic, gloves and other basic equipment – this could be a drastic strain that complicates care for other more common ailments.

Already the CDC is investing in Ebola containment efforts for the long haul, including by opening offices in Sierra Leone, Liberia and Guinea.

A Future of Surveillance

Dealing with endemic Ebola would necessitate the development and distribution of affordable and accurate Ebola diagnostic tests. Garry noted that the real-time PCR assay tests widely used in the current epidemic can be tricky to use in field hospitals, since the test must be done in a sterile environment with samples kept cool. Without adequate refrigeration or air conditioning, this isn’t easy. “We have tests for Ebola, but we’re just trying to get Ebola immune diagnostics to a point where they can be used for surveillance,” Garry said.

Another important tool will be genomic sequencing, to track the virus on a long-term basis and determine whether and how it is spreading. An important breakthrough in this epidemic was a study using genomic sequencing to trace the transmission chain of Ebola from a traditional healer’s funeral. Scientists have called for a network of genomic sequencing stations throughout West Africa.

But even if Ebola is again eradicated in the human population, the social factors that led to its explosion remain. That means there will very likely be future outbreaks originating from animals and quickly spreading through people in West Africa. In the Forest Region of Guinea where this epidemic started, humans have come into increasing contact with wildlife as forest has been cleared for planting crops, and as refugees from neighboring civil wars are crowded into the region. Meanwhile the increasing geographical interconnectedness of West Africa will mean viruses can quickly jump from isolated to urban areas.

“I don’t think people are going to stop clearing land or coming in contact with animals,” said Garry. “Has [Ebola] been [in West Africa] for 10 years or a thousand years? That’s not clear. But forever more, at least in our own corner of the world where we’re studying Lassa fever, we’re going to have Ebola.”

Still, in the massive toll of this epidemic, Garry sees one positive takeaway.

“Out of all this destruction and death, there could be a silver lining of having better attention of the international community helping these communities develop their healthcare infrastructure,” he said. “Typically in the past you get an outbreak, then it’s contained and people go away. Will there be a different mindset here now? People have maybe gotten some idea that this is a problem that can affect not just those tiny countries in West Africa, but have global implications.”

That could mean real improvements in health infrastructure if the international community is up to the challenge – or real consequences if they are not.


CATEGORIZED UNDER: Health & Medicine, Top Posts

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