Just as West Africa’s Ebola outbreak appears to be coming under control, researchers are warning that another public health crisis is looming in its wake. Major disruption of the region’s already feeble health care systems has derailed health campaigns targeting childhood diseases, leaving the door wide open for measles and other preventable illnesses.
In a study published in this week’s issue of Science, researchers led by Johns Hopkins epidemiologist Dr. Justin Lessler report that stress placed by Ebola on West Africa’s public health infrastructure has given rise to large, interconnected clusters of unvaccinated children throughout Guinea, Liberia, and Sierra Leone, the three countries hit hardest by the Ebola epidemic.
Using high-resolution population data and reports from local health officials, the researchers modeled the geographic distribution of unvaccinated children and the measles susceptibility for each country, before and after the outbreak. From these models, Lessler and his colleagues estimate West Africa’s “growing pool of susceptibility” could increase the size of a regional measles outbreak from 127,000 to 227,000 cases, resulting in anywhere from 2,000 to 16,000 deaths.
To be clear, that’s 2,000 to 16,000 additional deaths, on top of whatever death toll Ebola winds up causing directly. According to the latest figures from the World Health Organization, Ebola has now claimed more than 10,000 lives in Guinea, Liberia, and Sierra Leone. In other words, says Lessler, “the secondary effects of Ebola – both in childhood infections and other health outcomes – are potentially as devastating in terms of loss of life as the disease itself.”
Modeling a Measles Outbreak
West Africa’s current Ebola outbreak began 15 months ago, in December 2013. In their investigation, Lessler and his colleagues model several post-Ebola measles-outbreak scenarios, but assume in their main analysis that the Ebola outbreak will disrupt local health care systems for a total of 18 months.
The researchers also forecast a 75% drop in measles vaccination rates relative to pre-Ebola vaccination levels. A decline of this size would leave an estimated 1,129,376 children 9 months and 5 years of age vulnerable to measles infection, compared with 778,000 prior to the Ebola outbreak. The animation on the right depicts the accumulation of additional children susceptible to measles after each month of Ebola-related disruptions to vaccination efforts, under these assumptions [Credit: Justin Lessler and Saki Takahashi].
The prediction of a 75% drop in routine vaccination rates is based on surveys of local health officials, though Lessler and his co-authors note in their paper that the ever-changing nature of the Ebola epidemic limits the availability of reliable vaccination information. He said that recent information suggests his team’s primary scenario of a 75% decline “may have been a touch too pessimistic.”
“But even our least pessimistic scenario of a 25 percent reduction would be expected to result in tens of thousands of additional cases,” added Lessler, whose team also modeled scenarios involving 25, 50, and 100% drops in vaccination rate, over periods as long as 24 months. A 25 percent reduction following 18 months of disruption, says Lessler, would translate to between 500 to 4,000 additional deaths.
The researchers note that measles cases tend to follow crises — from political issues to natural disasters — since it’s a highly contagious disease against which we quickly lose herd immunity. In fact, says Lessler, a measles outbreak from 2010 to 2013 in the Democratic Republic of Congo — a country long plagued by political instability and civil unrest — led to nearly 300,000 cases and more than 5,000 deaths, many of them children under 5. Measles also accounted for scores of childhood deaths during a famine in Ethiopia in 2000.
Whatever the projected death toll in the current situation, the immediate course of action is clear: “[The] path to avoiding outbreaks of childhood vaccine-preventable diseases once the threat of Ebola begins to recede,” write the researchers, is “an aggressive regional vaccination campaign aimed at age groups left unprotected because of health care disruptions.”
Bracing for Ebola’s Aftermath
In the aftermath of the largest and most complex Ebola outbreak in history, measles is just one of many crises facing the region. Warning about the widespread impacts of the epidemic, the World Bank said Ebola may deal a “potentially catastrophic blow” to the West African countries reeling from the outbreak. Businesses are shutting down, people aren’t working, construction is on hold, kids aren’t going to school. A report from the bank in December 2014 noted:
GDP growth estimates for 2014 have been revised sharply downward since pre-crisis estimates. Projected 2014 growth in Liberia is now 2.2 percent (versus 5.9 percent before the crisis and 2.5 percent in October). Projected 2014 growth in Sierra Leone is now 4.0 percent (versus 11.3 percent before the crisis and 8.0 percent in October). Projected 2014 growth in Guinea is now 0.5 percent (versus 4.5 percent before the crisis and 2.4 percent in October).
The epidemic has also led to widespread food insecurity, and has increased the risk of sexual violence for women in girls in the region. Additionally, more than 3,600 children were orphaned after losing their parents to the virus.
Besides measles, people are going to suffer and die more from other diseases, too. “West Africa will see much more suffering and many more deaths during childbirth and from malaria, tuberculosis, HIV-AIDS, enteric and respiratory illnesses, diabetes, cancer, cardiovascular disease, and mental health during and after the Ebola epidemic,” wrote disease researchers Jeremy Farrar, of the Wellcome Trust, and Peter Piot, of the London School of Hygiene and Tropical Medicine, in an article in the New England Journal of Medicine.
The health and economic consequences will undoubtedly linger longer than the epidemic itself, and the fact that there will be a cohort of children who are unvaccinated will put Liberia, Sierra Leone, and Guinea at a higher risk of vaccine-preventable outbreaks for decades to come.
While Lessler’s team only looked in this study at measles risk, he said the Ebola epidemic had also disrupted delivery of vaccines against polio and tuberculosis and of a combined shot that protects against meningitis, pneumonia, whooping cough, tetanus, hepatitis B and diphtheria. The number of children not getting these vaccines in the region may be 600,000 to 700,000, he said.
“These setbacks have the potential to erode the substantial gains in the control of these diseases over recent decades,” Lessler said. “It could be a long time before the health care systems in the region recover from this.”