Thanks to widespread vaccination campaigns, NBC News reports, global health experts announced on Tuesday, September 27 that North, South, and Central America are now officially free of endemic measles cases.

Measles—which can cause brain swelling, pneumonia, and, in extreme cases, death—was once responsible for nearly 2.6 million annual deaths worldwide. In 1963, physicians developed a vaccination for the highly contagious airborne virus, and in the 1980s officials launched a 22-year campaign involving mass vaccination against measles, mumps and rubella throughout the Americas, the Pan American Health Organization (P.A.H.O.) said in a statement.

Today, measles is the fifth vaccine-preventable disease to be eliminated from the Americas, they added, along with smallpox, poliomyelitis, rubella, and congenital rubella syndrome.

Malaria was eliminated from America in 2002, and the Western hemisphere’s last case of endemic measles—meaning it wasn’t caused by an imported strain of the disease—was in 2002. (There have been documented cases of non-endemic measles in the U.S. since then. More on that later.) But even though it typically only takes a region three years to be declared free of a disease, it took 14 years this time around for officials to certify the fact, The New York Times reports. Experts attributed the lag to a variety of factors, including a lack of communication between local and national health departments; unvaccinated migrants; and war-torn regions that weren’t accessible for physicians.

Still, the P.A.H.O. warns, measles remains a global threat: In 2015, 244,704 measles cases were reported worldwide. To prevent imported cases, it’s important to maintain high vaccination coverage rates in the Americas, they said.

In late 2014 and early 2015, 125 people were diagnosed with measles. The initial outbreak is thought to have occurred in California’s Disneyland; it then spread to multiple states, Mexico, and Canada. The disease strain originated in the Philippines—but its rapid spread revealed that many kids aren't fully vaccinated. A study later revealed that around 9 million U.S. children are susceptible to measles, either because they haven't received the shots or because they aren't up to date with them.

[h/t NBC News]

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