(NEXSTAR) – More than 300 cases of measles, one of the most contagious viruses in the world, have now been confirmed across more than a dozen U.S. states, the Centers for Disease Control and Prevention announced Friday.

The actual case count is likely higher. The agency said it's aware of more "probable" measles cases that are still under investigation.

As of this week, the virus is now confirmed in three additional jurisdictions: Maryland, New York and Vermont. (Previously, measles had been........

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