WASHINGTON — The Centers for Disease Control and Prevention is urging Americans young and old to get vaccinated against measles because of a sharp uptick in cases in the new year.

Eighty-four people in 14 states have contracted the contagious respiratory disease in the first 28 days of 2015.

That’s “as many cases as we have all year in typical years. This worries me,” said Dr. Anne Schuchat, director of the CDC’s National Center for Immunization and Respiratory Diseases.

The vast majority of cases — 63 — are in California and stem from an outbreak that began at Disneyland Park in Anaheim.

Visitors to the park between Dec. 17 and Dec. 20 of last year later developed the disease along with at least five Disney employees. To date, 67 cases in California and six other states have been traced to the Disney outbreak.

“We don’t know exactly how this outbreak started, but we do think it’s likely a person who was infected with measles overseas visited the Disney park in December while they were still infectious,” Schuchat said Thursday during a telephone briefing with reporters.

In addition to the 63 cases in California, Arizona has reported seven cases, while Washington and New York have each seen two. Colorado, Nebraska, Oregon, Utah, Minnesota, Illinois, Pennsylvania, South Dakota, Texas and Missouri have reported one case each.

Growing in cells at the back of the throat and lungs, measles is spread through the air by coughing, sneezing and even breathing. It can cause fever and cold-like symptoms, along with a stubborn rash.

Before the U.S. measles-vaccination program, which began in 1963, 3 million to 4 million people in the U.S. developed measles each year, leading to 48,000 hospitalizations and 400 to 500 deaths.

As measles vaccinations took off in the 1960s, the rate of transmission steadily declined. The resurgence of the disease is a disturbing development for health officials, who declared in 2000 that measles had been eliminated from the U.S. through a successful vaccination program.

Between 2001 and 2010, the U.S. reported a median of 60 cases a year, Schuchat said.

But unvaccinated Americans and foreign visitors who traveled to the Philippines, Europe, Africa and Asia are the main culprits in a growing case spike that began several years ago and exploded in 2014.