The United States is experiencing a spike in measles, with 175 confirmed cases and 20 hospitalizations so far this year, according to the Centers for Disease Control and Prevention.

That’s about three times the usual number of cases of measles, CDC Director Thomas Frieden said Thursday. The U.S. has seen nine outbreaks this year, with the largest in New York, North Carolina and Texas.

More than 98 percent of measles patients were unvaccinated, Frieden said.

“This isn’t the failure of a vaccine; it’s the failure to vaccinate,” Frieden said.

In fact, measles has been officially eliminated throughout the Western Hemisphere.

The U.S. still had about 60 “imported” measles cases a year, however, largely diagnosed in travelers who come from abroad. Those cases mostly haven’t spread beyond a couple of people, however, because nearly everyone those travelers encountered was vaccinated.

The country’s safety net has become more porous in recent years, as like-minded parents who refuse vaccines have clustered in the same communities.

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