Measles has made a comeback, at least in New York City, where as many as 19 cases have been confirmed.

New York City isn’t an anomaly, though. Diseases that are and have been avoidable in the U.S. thanks to vaccines, are resurfacing all across the country. Measles, for instance, was considered wiped out in 2000, but there have been several outbreaks in the past few years. This map shows outbreaks of vaccine-preventable diseases since 2008 (click on “Map” and select which diseases and regions you want to see).

The emergence of these diseases — especially measles — is alarming, and mostly due to parents in the U.S. not vaccinating their kids. “If you are unvaccinated and you come in contact with measles, there’s a 90% chance you will get it,” says Jason McDonald, a spokesperson for the Centers for Disease Control and Prevention (CDC).

Though measles outbreaks are primarily linked to unvaccinated people, McDonald notes that some vaccines aren’t foolproof. For example, the whooping-cough vaccine may lose its efficacy over time. And, overall, most people do get their vaccinations. A CDC report looking at children entering kindergarten for the 2012–13 school year in all U.S. states found that more than 90% of these kids had their vaccines.

Still, there are people — including public figures and celebrities — who don’t vaccinate their kids and promote their choices. Most infamously, Jenny McCarthy has espoused her antivaccination position because she believes vaccines are full of toxins and cause autism. When she recently posed a question on Twitter about finding a mate, the vaccination backlash was loud and clear.

Just how harmful are these notions, though? Below are some preventable diseases making a vicious return thanks to people not getting their vaccinations.

Measles

According to the CDC, for every 1,000 children who get the measles, one or two will die. Currently, public-health workers are worried about the situation in New York, but just in the past three months, there have been reported cases of the disease in Massachusetts, Illinois and California. The CDC reports that from Jan. 1 to Feb. 28, 2014, 54 people in the U.S. have reported being infected with measles. On average, there are about 60 cases reported in the U.S. every year. Most people in the U.S. are vaccinated against the measles, but since measles is still around in other countries, those who travel outside of the U.S. can contract it if they are not vaccinated. New York City has not been able to confirm the source of the disease.

Mumps

As recently as Monday, health officials confirmed 23 cases of mumps at Ohio State University. In 2011, there was a mumps outbreak on the University of California at Berkeley campus, with 29 reported cases confirmed by the CDC. The source of the outbreak was thought to be an unvaccinated student who had spent time traveling in Western Europe where there is still a presence of mumps. In 2013, a slightly smaller outbreak of the disease broke out among students at Loyola University in Maryland. The last major occurrence was in 2006, when there was a multistate outbreak of 6,584 reported cases. Less than 20 cases a year was considered usual at the time.

Whooping Cough

Whooping-cough outbreaks are thought to be spurred by waning immunity from the vaccine. However, a 2013 study published in the journal Pediatrics reports that California’s worst whooping-cough outbreak, which infected more than 9,000 people, was also encouraged by a large number of kids who were unvaccinated.

Chicken Pox

In 2012, a county in Indiana experienced a major chicken-pox outbreak of more than 80 cases, which was thought to start from an unvaccinated child. The vaccine is 90% effective, so it’s possible for people who have been vaccinated to contract the disease.

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