The number of measles cases in the U.S. this year continues to climb, with the Centers for Disease Control and Prevention reporting 764 cases in 23 states as of late last week.
The latest numbers, announced on Monday, show 60 more cases since a week earlier.
“This is the greatest number of cases reported in the U.S. since 1994 and since measles was declared eliminated in 2000,” the CDC said in a release.
Pennsylvania is the latest state to join the list. It was reported last week that a Pittsburgh-area man, recently diagnosed with the disease, entered two grocery stores while contagious, local health officials said.
The 23 states that have reported measles cases to the CDC are Arizona, California, Colorado, Connecticut, Florida, Georgia, Illinois, Indiana, Iowa, Kentucky, Maryland, Massachusetts, Michigan, Missouri, Nevada, New Hampshire, New Jersey, New York, Oregon, Pennsylvania, Tennessee, Texas and Washington.
The CDC has attributed the unusually high number of cases to travelers who contract the disease overseas and then bring it to U.S. communities that have under-vaccinated populations. The states of Washington and New York have seen significantly large outbreaks, with those in New York some of the largest and longest-lasting since 2000.
“When measles is imported into a community with a highly vaccinated population, outbreaks either don’t happen or are usually small,” the CDC has said. “However, once measles is in an under-vaccinated community, it becomes difficult to control the spread of the disease.”
The health agency has warned that an estimated 30% of reported measles cases have one or more complications, and that for every 1,000 reported cases, there’s approximately one case of encephalitis and two to three deaths.