The California Department of Public Health announced on Friday that 49 cases of measles have been confirmed this year, compared to four confirmed cases at this time last year.
"This dramatic jump in the number of measles cases is a reminder to get fully vaccinated," CDPH Director and State Health Officer Ron Chapman said. "Being fully vaccinated against measles does more than just protect the person who receives the vaccination - it also protects their family and friends, including children who may be too young to be vaccinated."
Among the 49 cases, 11 patients reported travel outside of North and South America, including areas where measles is widespread and actively occurring. Among patients who did not travel outside the U.S., 30 had contact with known cases, three experienced contact with international travelers and five are still under investigation.
The CDPH said high immunization rates have kept preventable diseases at record lows during the past 20 years, ranging from four to 40 cases annually. It said that most cases of measles were linked to travel to parts of the world where measles is still common.
Children are recommended to receive the first dose of measles, mumps and rubella vaccine between 12 and 15 months of age. The second dose is typically administered when children are 4 to 6 years of age, before they start school.
The CDPH said adults do not need to receive MMR booster shots, but those born before 1957 who have not received two doses of the vaccine may not be fully inoculated.
Measles is highly contagious and spread through the air by cough or sneeze. Symptoms include fever, cough, runny nose, red, watery eyes and rash. Infected people are contagious for approximately eight days.