evidence: Dubious websites and citation-free social media posts have attempted to suggest that these measles outbreaks are the result of immigrants who illegally crossed into the U.S. via the Southern border — a common but almost-always-false trope employed by those who oppose more open immigration policies. For example, pro-conspiracy, anti-vaccine website Natural News claimed on 28 April 2019 that, "It’s the disease-ridden illegal aliens that are bringing infectious diseases into America" in a story titled in part, "The Measles Outbreak is a Massive False Flag." That report cited a story from Alex Jones' Infowars that misrepresented a Fox News segment about a measles outbreak in New York. [...] No factual basis exists to support the claim that illegal immigrants are the cause of the increase in U.S. measles outbreaks. But multiple pieces of evidence do support the claim that unvaccinated people who have traveled to areas with high rates of measles and then returned to the U.S. are the cause of the uptick. As of 30 April 2019, measles outbreaks — defined by the CDC as three or more simultaneous cases in the same area — were identified in nine geographic areas: [...] This New York measles outbreak, comprising 423 of the 704 individual infections, represents the vast majority of cases that are part of this troubling resurgence of measles in 2019. It was caused not by illegal immigration across the Southern border, but by unvaccinated American citizens traveling abroad in Israel — a country that is currently having its own measles epidemic. Similarly, the outbreaks in California have been tied to four cases of people traveling abroad and returning to the United States: