Federal health officials said Monday the United States recorded 21 new measles cases last week.
According to Reuters, that raises the total number of cases for the year to 1,203 across 30 states.
Officials at the Centers for Disease Control and Prevention say it's the worst outbreak of the virus since 1992.
The CDC said Monday there had been a 1.8% increase in the number of cases between August 8th and 15th, 2019.
Measles is highly contagious and in some cases deadly.