In the United States and around the world, immigrants tend to serve as convenient scapegoats for all manner of ills. Some politicians have even gone so far as to suggest that undocumented immigrants are making US citizens sick.
In July 2015, Donald Trump said that “tremendous infectious disease is pouring across the border” because of immigrants from Mexico and Latin America. Missouri’s Republican congressman Mo Brooks made a similar argument earlier that year, saying that Americans have died “because the diseases brought into America by illegal aliens who are not properly health care screened as lawful immigrants are,” and specifically suggesting that immigrants could be the cause behind the resurgence of the measles virus in the US. Former presidential candidate and retired neurosurgeon Dr. Ben Carson also jumped on the bandwagon, blaming measles and other infectious diseases on incoming undocumented immigrants.
But a recent paper in The Journal of Travel Medicine found what many people already suspected: immigrants are not to blame for measles outbreaks. In fact, it’s mostly international travelers who are spreading the disease around.
Researchers reached this conclusion by examining vaccination rates for the first dose of a measles-containing vaccine (“MCV1”) in the top international travel destinations for U.S. residents, including Mexico, Canada, the UK, the Dominican Republic, several European countries, and China). They also looked at vaccination rates for the most common home countries of incoming international travelers, which again included Canada, Mexico, and the UK, as well as Japan, Brazil, and China, among others, as well as unauthorized immigrants living in the US.
The results were striking. The research found that the total number of US residents traveling to countries with high measles incidence is 10 times higher than that of the cumulative number of unauthorized immigrants living in the US who come from countries where measles is common. And the number of international travelers coming into the US from these high-incidence countries was more than 14 times the number of unauthorized immigrants.
In other words, international travel by US citizens and foreign travelers legally coming to the US were much more likely to bring in a case of measles than undocumented immigrants. That’s both because there are far more international travelers coming to and from the US than there are undocumented immigrants, and because there were higher vaccination rates in the countries where many unauthorized immigrants originate.
What about legal immigrants? For example, could the decision to bring 10,000 Syrian refugees into the US put Americans at risk of measles importation?
Robert Bednarczyk, who led the study, doesn’t believe so. “We did cite, in our study, the need for legal immigrants to meet vaccination requirements, including measles vaccination, prior to coming to the US. So I do not believe that increases in legal immigrants would increase susceptibility to measles in the US population.”
Skeptics of the recent findings may point to the current measles outbreak in the US in an immigrant detention center in Arizona. Twenty-two cases have occurred there since May. While it’s uncertain whether the first case was due to an immigrant or a staff member, officials acted quickly to vaccinate any of the detainees who had not received the measles vaccine, limiting the outbreak in the detainee population. Bednarczyk notes this outbreak “does fit with our findings. With 12 cases of measles in the detainees, who number well over a thousand, it does not appear that there is widespread lack of vaccination within those detainees, given that the vaccine effectiveness for two doses of measles vaccine is about 97%. Because of how infectious measles is, it is not surprising that it found the susceptible individuals in the larger detainee population.”
In fact, what has allowed the measles outbreak in Arizona to spread is a homegrown problem: lack of vaccination among our own citizens. While the detainees held at the center received vaccinations if necessary, staff of the privately-run prison and immigration company were not all up-to-date, propagating the outbreak within the prison and spreading it to outside community members. Arizona’s measles vaccination rate has been declining since 2010, and is among the worst in the nation, according to the Centers for Disease Control and Prevention. Seven people from Arizona were also infected during the 2014 Disneyland measles outbreak, which is thought to have been sparked by an international traveler, again emphasizing the risks both of incoming travelers to begin an outbreak, and unvaccinated citizens to spread it further.
The largest measles outbreak in 2014, in Ohio’s Amish country, was also started by an international traveler. Unvaccinated Amish missionaries traveled to the Philippines, where a measles outbreak was underway, and brought the virus back to their community.
There are, however, a few straightforward ways to reduce measles outbreaks in the US. International travelers heading out of the US should get their recommended vaccinations beforehand, lest they bring the virus back home as an unintentional souvenir. And we should maintain high vaccine coverage throughout the US to minimize the chance of measles, or other preventable infectious diseases, spreading. As with so many things, the greatest danger to Americans is not coming from the outside.
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