The end of Liberia’s Ebola epidemic may be in sight, according to a new analysis that predicts the outbreak could be contained in Liberia between March and June of this year, with a rapid decline in new cases following June 2015.
The findings, published in the latest issue of the journal PLOS Biology, are based on new computer model that takes into account not only features of the virus and how it transmits, but also what is being done to halt its spread. Using actual epidemiological data instead of estimates, the model produces a far more limited range of future scenarios that gives scientists a more accurate picture of the most likely trajectory.
Scientists initially thought that even if almost every infected person could be hospitalized, it wouldn’t stop the rapid spread of the Ebola virus for months to come. The new model offers a much more optimistic outlook, predicting that Ebola transmission in Liberia — which at one point had the biggest explosion in new cases — could be brought to an end within the next few months.
The study does caution that “continuing on the path to elimination will require sustained watchfulness and individual willingness to be treated,” and the researchers were careful to point out that this hopeful news is only possible if the current rate of hospitalization continues and the same careful protocols are followed both in the hospitals and out in the community.
“The [projections] are a realistic possibility but not a foregone conclusion,” says Dr. John Drake, an ecology professor at the University of Georgia (UGA), who led the project to develop the model with other ecologists at UGA and Pennsylvania State University.
Liberia — along with Guinea and Sierra Leone — is one of the three countries hit hardest by this epidemic, which in August was declared a “Public Health Emergency of International Concern” by the World Health Organization. According to the latest figures from WHO, there have been at least 8,331 Ebola cases and 3,538 deaths in Liberia since the start of the epidemic, with 48 new cases in the past 21 days. WHO officials confirm that the number of new cases in Liberia has been slowing significantly in recent weeks, halving every 21 days on average. Last week, fewer than 10 cases were reported nationwide.
Model shows adequate treatment capacity is key to ending outbreak
In coming up with their predictive models, the researchers took into account data from previous outbreaks of Ebola, as well as probabilities about infection rates among healthcare workers, family members of the infected and those who are exposed to the virus during burials.
The team concluded that in order for Liberia’s Ebola outbreak to end, new hospital beds would have to be added at the same current rate (300 were provided between July and September 2014). That would allow 85% of infected patients to be treated with the nutritional and hydration therapy that is critical to overcome the infection. It would also ensure that clinics have sufficient capacity to isolate infected patients, which is considered key to stopping the spread of the disease. If new beds aren’t continually added, then hospitalization rates could drop back down to 70%, and cases may start to outpace public health workers’ ability to contain the disease, the researchers found.
Burial practices need to change as well. Cultural norms include touching the bodies of the deceased, which are highly contagious and often results in infection. Safer burial practices, in which infected patients are isolated from healthy people, are keeping transmission levels under control, the authors say.
The key to reducing the number of Liberia’s Ebola cases by summer is ensuring that anyone who is sick is hospitalized. “These modeling exercises suggested that in the absence of rapid hospitalization of most cases, none of the proposed scenarios for increasing hospital capacity would have been likely to achieve containment,” the authors write.
Epidemic could last through 2015 in Guinea and Sierra Leone
Although he new findings offer hope for Liberia, officials are still struggling to bring the outbreak under control in neighboring Sierra Leone and Guinea, where progress has been uneven and slow. Sierra Leone, which has been hit hardest by the epidemic, has confirmed 10,124 Ebola cases and 3,062 deaths, while Guinea, where the epidemic started, has confirmed 2,806 cases and 1,814 deaths. And those numbers are believed to be low due to widespread under-reporting of cases, says the WHO.
According to the most recent situation report by the WHO, Ebola case incidence is still up and down in Guinea, “with no identifiable downward trend.” In Sierra Leone, there are signs that incidence has leveled off, “although transmission remains intense in the west of the country.” Of particular concern are new flareups in hard-to-reach rural parts of Guinea and ongoing Ebola transmission in and around the capital cities of both Guinea and Sierra Leone.
While there are reasons for optimism, health officials have cautioned against becoming complacent. Dr. Tom Frieden, the head of the Centers for Disease Control and Prevention, said recently that as the infection rate slowed down briefly, health care workers were “relaxing their grip” by not wearing protective clothing and not taking enough precautions. Speaking after a recent visit to Liberia, Guinea and Sierra Leone, Dr. Frieden said he saw “real momentum and real progress” in combating the virus, but added: “It’s going to be a long hard fight… The challenge is not to let up, not to be complacent and to really double down.”
He stressed that the response to the outbreak must not let up until the number of cases drops to zero; with a disease like Ebola, even one case in the community is enough to reignite an outbreak — in fact, the 2014 epidemic has been traced back to a single two-year-old child. “… [G]oing forward, the challenge is to get to zero,” Dr. Frieden said. Until then, “we in the U.S. will not be safe from other potential imported cases … [and] we can’t be sure that the disease won’t spread to other countries and potentially develop more challenging patterns,” he warned.
Given the current situation, experts say the Ebola epidemic in these countries will likely last through 2015, though its devastating impact on West Africa will persist for much longer. According to a recent World Bank report, the socioeconomic effects of Ebola “put the current and future prosperity” of the region at risk, with a potential economic cost of $32.6 billion by the end of 2015.