Measles is on the rise in the United States. These graphs show how bad the situation has gotten

The United States is experiencing its worst year for measles since 1991. Since the start of last year, large outbreaks have been reported in several states, including Texas, Utah, South Carolina and, now, Pennsylvania.

The year’s cases have come in waves, one earlier this year and another as summer turned to fall.

Measles cases have been reported across the country. Pennsylvania, South Carolina and Utah saw the most. Only five states have reported no cases.

Measles was declared eliminated in the United States in 2000, meaning the disease is no longer continually spreading in the country. For years, the United States had relatively few cases. Now, pockets of unvaccinated residents are allowing outbreaks — defined as three or more linked cases — to arise.

Children and adolescents account for most of the confirmed cases. The overwhelming majority of people who contracted measles were unvaccinated or had unknown vaccination status.

Public health officials agree that the best way to protect yourself against measles is to get vaccinated.