With West Africa's Ebola epidemic passing the 1-year mark, two new reports yielded details about factors that fueled the event, including bats in a hollow tree that may have infected the index patient, a young Guinean child, and a silent chain of transmission that caused the disease to flare again in May after cases had sharply dropped off.
Also today, the World Health Organization (WHO) updated its Ebola numbers, saying there have been 20,129 cases, along with 7,879 deaths, in the three hardest-hit countries. The data include cases reported through Dec 28 in Guinea and Sierra Leone and through Dec 24 in Liberia. The totals reflect an increase of 48 cases and 37 deaths since the WHO's update yesterday.
In addition, the WHO today posted a new timeline of the event, starting with its African regional office's first report on the outbreak on Mar 23.
Bat colony suspected as virus source
The bat study, by a multidisciplinary group of German-led researchers, was conducted in April in the area around Meliandou, a village in a plantation region of Guinea where a 2-year-old boy thought to have been the index patient lived. The team published its findings today in an online edition of EMBO Molecular Medicine.
The 4-week investigation of the roots of zoonotic transmission where the outbreak began involved a field team that included anthropologists who looked at human exposure to bush meat and bats, ecologists who surveyed local wildlife, and veterinarians who analyzed samples from bats and other animals.
In other Ebola outbreaks, the virus was known to take a toll on larger animals, such as wild apes. However, the team found no evidence of population declines in the region's wildlife populations. Also, children and women were among the first victims in the outbreak, rather than hunters, also suggesting that the virus probably didn't jump from a larger animal.
Hunting and butchering fruit bats—a suspected Ebola reservoir—were common activities in southern Guinea, providing a link to humans. Also, the team found that children often hunt and grill insect-eating bats in and around villages, providing more exposure to the animals.
Though the group didn't find any large colonies of bats in or near Meliandou, villagers showed them a large tree stump from a hollow tree near which the village children, including the index case, frequently played, catching and playing with bats. They said the tree burned on Mar 24, triggering a "rain of bats" that were collected to eat. However, the local people disposed of them after authorities the next day imposed a ban on consuming bush meat.
Genetic sequencing of the environment near the tree confirmed that small free-tail bats had been in the area, the same type the villagers described.
The team said the circumstances may have led to a massive exposure to bats, similar to events in bat-inhabited caves that have been implicated in the zoonotic transmission of Marburg virus. They added that their findings confirm the index case but suggest a slightly different transmission timeline, with the virus spreading to other parts of Guinea, then to Sierra Leone and other countries. Local people told the researchers that the boy died on Dec 28, several weeks later than the Dec 6 date reported in the medical literature.
Times piece describes missed opportunities
An undetected transmission chain was one of several missteps that led to the Ebola outbreak's unprecedented size, according to an in-depth look at the events by a team of reporters from the New York Times. The report, based on a 2-month investigation, was first published yesterday.
The report describes how experts thought the outbreak was close to burning itself out, with sharply declining at the beginning of May, along with clues they may have missed that an unusual event was about to unfold, and missteps in the response.
Focusing on the time frame of the lull and the spike that followed, the team found that WHO and Guinean officials documented a handful of suspected cases across the border in Sierra Leone in March, but that information about two of the cases never got to senior health officials and investigators. This circumstance appears to have led to a chain of transmission that went unchecked for 2 months and didn't surface until late May, when Sierra Leone confirmed its first Ebola case.
The report also says the same two cases that fell through the cracks sparked a second wave of illnesses in Liberia that began in late May.
Experts involved in the early response told the reporters that they didn't deploy enough staff to the region and pulled them too soon. They also described management glitches by the WHO, which was stretched thin by budget cuts and other health and humanitarian crises.
Other factors that hobbled the response included some officials' downplaying of the Ebola threat and public education campaigns that did more harm than good, such as early efforts that highlighted the lethality of the disease.
In tracing the first illnesses, including the boy who had the index case, investigators made faulty assumptions, and it took 12 weeks to determine that the illnesses and deaths were caused by Ebola, according to the report.
The WHO's African regional office, initially appointed to lead the response, was suffering from sharp cuts in preparedness money and staff and was overmatched in its ability to handle the task, and it posed bureaucratic roadblocks in getting help from global experts, the article says.
In the first few months of the outbreak, lack of cross-border coordination hampered the response, and officials arriving from outside West Africa lacked a full understanding of the political and cultural challenges they would face, including deep distrust of government.
The Times team pointed out that Doctors without Borders declared the outbreak out of control on Jun 21, but the WHO didn't declare a public health emergency of international concern until Aug 8.
Health officials who spoke with the Times said they wish they had devoted more staff and resources to the outbreak early on and had recognized how weak contact tracing was and the distinct culture of West Africa.
Pierre Rollin, MD, a top Ebola expert at the US Centers for Disease Control and Prevention, who was quoted extensively in the Times report, said some of the events couldn't have been predicted, especially in the midst of an unfolding crisis. "There were a lot of things we didn't know at that time. No one could have imagined that it would be what we have now," he said.
Dec 30 EMBO Molecular Medicine study
Dec 29 New York Times story
Dec 30 WHO timeline
Dec 30 WHO situation summary