An international study involving the University of Southampton suggests there could be a rise in measles cases of 100,000 across the three countries most affected by the Ebola epidemic in West Africa due to health system disruptions.
The research in the journal Science, led by Princeton and Johns Hopkins University in the USA, predicts that the size of a measles outbreak will increase from 127,000 at the start of the Ebola epidemic in early 2014, to 227,000 after 18 months of the outbreak. This would result in an additional 5,000 measles deaths, and potentially as many as 16,000 – double the number of reported Ebola deaths. Both increases are due to an interruption in the childhood immunisation programmes of Guinea, Liberia and Sierra Leone, due to huge demands placed on their healthcare systems.
A team of researchers from the US and UK used sophisticated modelling techniques to project the likely spread of measles – taking into account factors such as, birth rates, infection susceptibility and population rates.
Dr Andy Tatem, a geographer at the University of Southampton, provided high-resolution map data for the project, showing detailed information on population distribution and age structures. This WorldPop data is derived from official national statistics, household surveys, birth rates, satellite imagery and other sources.
Dr Tatem comments: “The Ebola epidemic is one of the worst public health crisis in recent memory causing tens of thousands of people to become critically ill and thousands more to die. It has also caused severe disruption to health care services in the affected countries, including childhood vaccination programmes – thus creating a second public health risk.
“The disruption in recent months has led to a pool of unvaccinated children building up across West Africa – leaving them susceptible to measles and opening the door to a large increase in cases.”
Overall, it is estimated measles immunisation in West Africa has fallen by 75 per cent because of Ebola*. Using this figure, the report authors have predicted that after 18 months of healthcare disruption 1,129,376 children aged between 9 months and 5 years will be left unvaccinated – compared with 778,000 prior to the crisis.
Dr Tatem comments: “Our study shows it is crucial to have an aggressive regional vaccination programme ready to run, as soon as the threat of Ebola begins to recede, to help counter the steep downturn in immunisation rates. Understanding how measles is likely to spread geographically and where best to concentrate interventions will be vital to an effective response.”
Measles epidemics often follow humanitarian crises because the infection is one of the most transmissible and vaccination rates tend to be lower. The three main Ebola affected countries had seen a marked fall in cases in recent years due to vaccination efforts. Between 1994 and 2003, together they reported over 93,000 cases, but this fell to just under 7,000 in the decade from 2004.
Measles is just one of several childhood illnesses which have suffered limited vaccination distribution because of the Ebola epidemic. Immunisation against meningitis, tuberculosis and polio has also been affected. Similarly, there has been a negative impact on interventions against malaria and HIV. The report authors call for the deployment of simultaneous public health interventions to tackle these problems.
* Scenarios were also considered in the study for 25, 50 and 100 percent reductions in vaccination rates.