More than 100 people from 21 states were reported to have contracted measles in the first half of 2018, the Centers for Disease Control and Prevention says on its website.
There have been a total of 107 cases of measles between Jan. 1 and July 14, 2018. The cases were reported in D.C. and states including California, Connecticut, Florida, Maryland, New Jersey, New York, Pennsylvania and Texas.
The majority of people who have contracted measles were unvaccinated, the CDC says.
Because measles is common in other parts of the world, including some countries in Europe and Asia, travelers with measles can bring the disease in the U.S. The disease can spread within the U.S. when it reaches a community with groups of unvaccinated people.
Symptoms of measles include high fever, cough, runny nose and red, watery eyes. A rash also forms three to five days after symptoms begin. The disease very contagious and can spread through coughing and sneezing
The U.S. experienced a record number of measles cases in 2014 with 667 reported cases from 27 states. It was the greatest number of cases since elimination of the disease was documented in the U.S. in 2000.
There was also a large, multi-state outbreak in 2015. It was linked to an amusement park in California, likely originating from a traveler who got infected abroad before visiting the park. A total of 188 people from 24 states and D.C. were reported to have gotten measles.
In 2017, 118 people from 15 states and D.C. A total of 86 people from 19 states contracted the disease in 2016.