United States authorities have quarantined thousands of immigrant detainees in an attempt to contain the spread of mumps and chicken pox in multiple detention centers. According to CNN, Immigration and Customs Enforcement has recently recorded cases of one or both diseases in more than 39 facilities. About 5,200 detainees have been quarantined for exposure (though significantly fewer people have actually shown symptoms).
News reports of the quarantine have renewed fears that immigrants could bring infectious diseases into the U.S. But as I wrote for Pacific Standard in May, the connection between the border and disease has little to do with where migrants are coming from, and much more to do with the conditions they find themselves forced into on the border. That month, overcrowding in a migrant shelter on the Mexican side of the border had led to a chicken pox outbreak.
Now, severe overcrowding on the other side of the border—in U.S. border detention facilities—could be contributing to the spread of disease. Last month, an internal government investigation into the conditions in Customs and Border Protection holding facilities revealed incredibly cramped conditions. A facility meant to house a maximum of 125 people had been packed with up to 900 detainees. Inspectors found that some rooms had "standing room only"—meaning detainees are forced to stand shoulder to shoulder, without room to even sit down, for "days or weeks."
This sort of overcrowding has led to disease outbreaks in refugee and migrants camps before. As I wrote in May, a major study analyzing migration patterns from as far back as 1994 found that immigrants don't bring disease into their new countries (in fact, an increasing immigrant population was found to correlate with healthier host countries). However, migration can be associated with disease when migrants are forced to live in squalor:
Another review of multiple studies of migrant and refugee health in Europe came to a similar conclusion [that immigrants don't spread disease], with an added caveat: Though the risk of migrants and refugees spreading diseases to a host populations was found to be "very low," the risk of disease for refugees themselves was higher, mostly "due to poor living conditions" they faced in European camps.
When the 2018 mid-term elections brought international attention to two of the migrant "caravans" that made their way north from Central America, conservative news outlets repeatedly fanned the flames on unfounded fears that migrants brought diseases like Ebola and leprosy with them. Some raised concern about whether or not Central Americans were sufficiently vaccinated, but there are indications that they may in fact be better protected than Americans:
For many diseases—like measles, diphtheria, and polio—Nicaragua, Honduras, Costa Rica, and Mexico all have higher vaccination rates than the U.S. Even Guatemala, which lags behind the U.S. in average vaccination rates (80 percent compared to the U.S.'s 89 percent), has a higher vaccination rate for measles than many of the areas where outbreaks have occurred in the U.S.