SOURCES: April 17, 2015, Morbidity and Mortality Weekly Report; California Department of Public Health
THURSDAY, April 16, 2015 (HealthDay News) -- A measles outbreak that began last December at two Disney parks in California will officially be over if no new cases are reported by Friday, state health officials said.
According to the California Department of Public Health, a total of 134 people in California have been diagnosed with measles since the outbreak started.
However, additional cases were reported outside of California, and the U.S. Centers for Disease Control and Prevention reported on Thursday that the latest total in the outbreak was 159 cases.
Since the outbreak began, a debate over the anti-vaccine movement has been reignited, because a significant number of people infected had not been vaccinated against the highly contagious disease or had only received one dose of the vaccine that protects against measles. Two doses of the vaccine are recommended.
According to the CDC, over 80 percent of all of the cases in the outbreak occurred among people who were unvaccinated or had an unknown vaccination status. The Disney outbreak accounted for 70 percent of all measles cases this year, the agency added.
And California health officials said in their latest measles report that of the patients for whom they have documentation, 57 of the 134 cases were unvaccinated, while another 25 had one or more doses of the measles vaccine. The disease also hit adults the hardest, with 55 percent of California residents diagnosed with measles in the outbreak aged 20 and older.
Health officials have explained that vaccination rates have to be very high to protect an entire population against an infectious disease, but they say that the anti-vaccine movement has lowered those rates.
Although measles was declared eliminated from the United States in 2000, "approximately 20 million measles cases occur [worldwide] annually, and importations to the U.S. will continue to place unvaccinated populations at risk for measles," CDC researchers reported in the April 17 issue of the Morbidity and Mortality Weekly Report, a CDC publication.
Therefore, "measles transmission in pockets of unvaccinated persons increases the risk for transmission to vulnerable groups, such as those who cannot be vaccinated because of underlying medical conditions, or infants too young to be vaccinated," the researchers added.
"The continued risk for importation of measles into the United States and occurrence of measles cases and outbreaks in communities with high proportions of unvaccinated persons highlight the need for sustained, high vaccination coverage across the country," corresponding author Nakia Clemmons, and colleagues at the CDC, concluded.
Measles symptoms can include fever, cough and watery eyes followed by a telltale rash. A measles outbreak is considered over when 42 days -- or two incubation periods -- have passed since the last onset of the rash, according to the California Department of Public Health.
Visit the U.S. Centers for Disease Control and Prevention for more about measles.