Mike Stobbe

NEW YORK: Measles cases are accelerating, and in the last five months have caused more U.S. illnesses than in any entire year since 1996.

Health officials say 307 cases have been reported since New Year’s Day. About half have been in the past month — most from a huge outbreak in unvaccinated Amish communities in Ohio.

Cases have been reported in 18 states and New York City; Ohio led with 138 cases, followed by California with 60 and New York City with 26.

Ohio cases have been reported in Ashland, Coshocton, Holmes, Knox, Richland and Wayne counties — with the bulk of the illnesses in Knox.

The CDC released the latest numbers Thursday during a news conference.

“Measles has reached a 20-year high. This is not the kind of record we want to break,” said Dr. Anne Schuchat of the Centers for Disease Control and Prevention.

Nearly all the cases have been linked to travelers who caught the virus abroad and spread it in the United States among unvaccinated people. Many of the travelers — including Amish missionaries — had been to the Philippines, where a recent measles epidemic has caused more than 30,000 illnesses.

Most of the unvaccinated skipped shots for personal or philosophical reasons, Schuchat said.

About half of those who got sick have been adults 20 or older. At least 43 people were hospitalized with measles complications — mainly pneumonia. There have been no deaths. No measles deaths have been reported in the United States since 2003.

The measles virus is highly contagious, spreading easily through the air and in closed rooms. Infected droplets can linger for up to two hours after the sick person leaves.

It causes a fever, runny nose, cough and a rash all over the body. In rare cases, measles can be deadly, and is particularly dangerous for children. Infection can also cause pregnant women to have a miscarriage or premature birth.