Europe hit a record-low number of measles cases in 2016; the World Health Organization recorded just over 5,200 cases of the disease. But a year later, measles cases have spiked to over 21,000 across the Continent.
Almost a third of the 53 countries in the European region saw large outbreaks of over 100 cases of measles in 2017. The largest outbreaks affected over 5,000 people each in Romania and Italy, and just under 5,000 in Ukraine. The disease ultimately killed 35 people in Europe last year.
WHO ascribes some of the larger measles outbreaks to an overall decline in vaccination rates. That's likely due in part to fears about the since-discredited link between vaccines and autism. Disruptions in vaccine supplies and low vaccination rates in marginalized communities also contributed to the outbreaks.
Europe was on track to becoming measles-free. Thirty-three countries have "eliminated" the disease by boasting high enough immunization rates to prevent it from spreading through the population for at least three years.
But even countries that declare victory over measles can still have immunization gaps and outbreaks. The U.S. eliminated measles in 2000 but saw 118 cases of the disease in 2017.