In 2000, a panel of experts was brought together by the Centers for Disease Control and Prevention (CDC). They came to discuss whether measles was still endemic in the United States, that is whether it still existed in the general background of US infectious diseases. They concluded that measles had been eradicated in the US, and that the occasional cases imported from abroad were stopped by a wall of vaccinated Americans.

Welcome to the future. The US is in the middle of its largest measles outbreak since 1996. Most of the cases originated abroad, brought back by unvaccinated travelers, either American residents or foreign visitors. This has so far led to 12 outbreaks (that is, a cluster of three or more connected cases) mostly among the unvaccinated. Of the 139 cases who were US residents rather than foreign visitors, twelve had documentation of adequate immunization.

The surprise isn’t that a few cases should slip through the wall of vaccination, but that the wall has so many chinks in it. The number of measles cases being imported, and the falling vaccination rates of Americans may reach the point soon where we no longer need to import our measles as it will once again become endemic.

Measles isn’t just a curious disease that we learned about in medical school (“cough, coryza, conjunctivits”); it’s a serious disease that leads to pneumonia in 1 in 20 children, and brain inflammation in 1 in 1000. Outside the US, it causes hundreds of thousands of deaths yearly.

We must increase our efforts to vaccinate all US residents properly (including undocumented residents). If measles does take hold once again in the U.S., the blame will fall squarely on our health care system’s failure to deliver vaccine, and on those who for whatever reason delay or avoid vaccination altogether.

It used to be that Americans viewed public health battles with excitement, a battle against fear itself, against the fear of children choking to death from whooping cough, or becoming paralyzed by polio. Now, as we sit behind our crumbling shield of vaccination, we have become complacent. If we fail to act, our complacency will be replaced by very real fears, especially for our children.

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