The recent influx of migrants to Europe has plenty of people concerned that these refugees are bringing disease into their countries. It is true that a small number of cases of measles, along with other infectious diseases, have been traced back to immigrants from countries with less robust healthcare. But the rise in measles cases isn't due to incoming refugees. One 2015 study found that, across 13 European nations, 7.1 percent of all measles cases were due to migrants. Similarly, in the U.S. two separate studies have found that the vast majority of measles cases come from U.S. residents, and that number is only rising. From 2001-2008, 79 percent of cases were from citizens returning from travel abroad, whereas from 2009-2014 it was 93 percent. Most of them were unvaccinated. The WHO's report agrees: "experience has shown that, when importation occurs, it involves regular travellers, tourists or health care workers rather than refugees or migrants." They do recommend that countries vaccinate refugees who might be susceptible to certain disease so that any outbreaks that occur in migrant camps will be limited, but they continue to stress that it is vacationing citizens—not refugees—who bring in the majority of these diseases.