ATLANTA (AP) — Health officials say 2013 already is one of the worst years for measles in more than 15 years.

Before a vaccine became available about 50 years ago, nearly all children got measles by their 15th birthday. In those days, nearly 500 Americans died from measles each year.

Now, the nation has about 60 cases each year. But so far this year, officials have seen 159 cases. The highest count since the mid-1990s was 222 in 2011.

Most young children are vaccinated against measles. But outbreaks still occur, usually when travelers pick up the measles virus abroad and then spread it among unvaccinated people here.

Nearly all of this year's cases have been traced to travelers.

___