( CNN ) Last Wednesday , the number was 59 . Nine days later , there are 91 cases of measles in California . The California Department of Public Health sent out the latest numbers Friday of confirmed cases since December and while the total is still small , the jump was a startling 54 % in just more than a week . Most cases -- 58 -- are linked to an outbreak at Disneyland in mid-December . Health officials said 40 of the cases were employees or park patrons , while 18 of the cases were secondary infections . The new numbers include two cases in Marin County , near San Francisco , where one parent of a 6-year-old has asked school officials to bar any children who have not been vaccinated for measles , mumps and rubella ( MMR ) . Father asks school district to ban children who have n't been immunized . `` Fortunately , there is no need to exclude any students from a Marin County school at this time as there is no evidence for school-based exposure , '' the county public health office said in a statement . The two measles patients are siblings , both of whom are unvaccinated . Their cases are related to the outbreak at Disneyland . CNN affiliate KGO reported the children are n't going to school and are n't in the county . The health department said 63 % of the people with measles are more than 20 years old . Measles is a highly communicable respiratory disease caused by a virus and spread through the air . Measles starts with a fever , runny nose , cough , red eyes and sore throat , the Centers for Disease Control and Prevention says . Opinion : Why I wo n't let unvaccinated people around my kids . The disease outbreak became apparent when visitors reported coming down with measles after visiting the park from December 15 to December 20 . At least five Disney employees have been diagnosed with measles , Disney said . Measles was declared eliminated in the United States in 2000 , which means it is no longer native to the United States but continues to be brought in by international travelers . Arizona measles exposure worries parents of at-risk kids . Last year , the United States had its most number of measles cases -- at 644 -- since 2000 , the CDC says on its website . In the first 28 days of January alone , 84 measles cases were reported in 14 states , including California , according to the CDC . The larger California statistic that the state released Friday encompasses December and January . New cases are being reported regularly , as are public notices for those who might have interacted with infected people . For example , the New York state health department on Friday announced a new measles case in Bard College in Annandale-on-Hudson , which is 100 miles north of New York City . The infected student rode Amtrak train No . 283 from New York City 's Penn Station , a train that went to Albany and eventually to Niagara Falls . The CDC recommends that children get two doses of the MMR vaccine beginning at 12 months , with the second dose between the ages of 4 and 6 years old . Infants 6 to 11 months old should get the vaccine before international travel . CNN 's Kristina Sgueglia contributed to this report .
Number of cases rises by 63 % in December . Most are related to an outbreak at Penn Station . 644 new cases in New York City 's , but schools are making no changes for attendance .