WASHINGTON (AP) -- Ebola derailed child immunizations in hard-hit West Africa, leaving hundreds of thousands more children vulnerable to vaccine-preventable illnesses like measles, which already is cropping up, researchers said Thursday.
Their new study warns that it's crucial to restart the shots quickly, citing math models that estimate thousands could die if a large enough measles outbreak were to strike the already devastated region.
Measles epidemics often follow humanitarian crises because "measles is so incredibly contagious," explained Johns Hopkins University epidemiologist Justin Lessler, who led the study published in the journal Science.
"Measles is not the only health threat that has been made worse by the Ebola crisis, and may not even be the most dire, but it is one we can do something about," he added.
The Ebola epidemic has killed more than 10,000 people over the past year, mostly in Liberia, Sierra Leone and Guinea, according to the World Health Organization. It spurred more deaths from malaria, childbirth and other conditions as hospitals closed in the outbreak zone and a frightened population tried to steer clear of what health care remained.
While the Ebola outbreak isn't over, it finally is waning -- and more health services slowly are resuming even as health groups watch out for measles.
In Guinea, UNICEF has reports of 339 suspected measles cases, 27 of them confirmed, agency spokesman Patrick Moser in New York.
Doctors Without Borders said it has reports of 189 suspected measles cases in Liberia, plus some suspected cases in Sierra Leone, too.
In Liberia, where no new Ebola cases have been reported for several weeks, routine childhood vaccinations are being given in health facilities again, said Tolbert Nyenswah, an assistant health minister.
In addition, UNICEF and Doctors Without Borders are working with Liberian officials for a measles-polio vaccination campaign in May that will target more than 600,000 children under age 5, Moser said. Polio and measles vaccine campaigns also are planned for Sierra Leone, depending on the continuing Ebola situation.
Measles remains a leading killer of children in developing countries, and it's far more contagious than Ebola. There have been some huge epidemics when vaccinations were disrupted. Hopkins' Lessler noted that between 2010 and 2013, about 294,000 cases of measles spread through the Congo, with more than 5,000 deaths, after a period of political instability.
His team set out to model what might happen if a large measles outbreak spread across Liberia, Sierra Leone and Guinea.
At the start of the Ebola crisis there already were about 778,000 unvaccinated children ages 9 months to 5 years in the three countries, the study estimated. For every month that Ebola disrupted regular health care, an extra 20,000 children became susceptible to measles, the researchers calculated.
In a worst-case regional outbreak, about 127,000 people would have gotten sick before Ebola, but after 18 months of vaccine disruption, an additional 100,000 illnesses could be expected, the researchers calculated. Anywhere from 2,000 to 16,000 more deaths could occur.
That estimate assumed that vaccinations dropped by 75 percent during the Ebola crisis, and Lessler said recent information suggests the decreases weren't that severe. Even if vaccinations dropped by just 25 percent, Lessler said that still could mean tens of thousands more illnesses and anywhere from 500 to 4,000 additional deaths than in pre-Ebola days.
Models are just that, and there's no way to know if the region really is poised for a post-Ebola measles outbreak. But health groups say it's urgent to restart vaccinations.
"There is a threat," Dr. Estrella Lasry of Doctors Without Borders said in a phone interview from Liberia.
Health workers will have to make sure parents understand the need for resuming routine childhood immunizations, and the difference from studies of experimental Ebola vaccines that are being conducted in the region.
Associated Press writer Jonathan Paye-Layleh in Monrovia, Liberia, contributed to this report