The number of U.S. measles cases through the first three months of this year have surpassed the count for all of 2018, health officials say.
There have been 387 cases through March, the Centers for Disease Control and Prevention reported Monday. There were 372 last year.
The numbers are preliminary, and may change. But the 2019 tally is already the most since 2014, when 667 were reported.
This years numbers have been driven by outbreaks in several states, including New York, California, Illinois, Texas, and Washington.
Most people who get measles have not been vaccinated. In the U.S., most outbreaks are sparked by travellers who picked up the virus in countries where measles is more common.
Nearly 83,000 people contracted measles in Europe in 2018, the highest number in a decade, according to the World Health Organisation.
The measles vaccine is 97 per cent effective, according to the CDC.
Measles is spread through the air when an infected person coughs or sneezes, and it is extremely contagious.