An estimated 79% of measles cases this year have come from 15 outbreaks. The largest outbreak occurred in Ohio, where the current number of cases stands at 164, according to the state's Department of Health website. Ohio health officials say the outbreak in that state began when unvaccinated travelers caught the virus while visiting the Philippines, which is experiencing a large outbreak that has resulted in more than 6,000 confirmed cases and 41 deaths as of April 20. So far, no measles-related deaths have been reported in the U.S.
Of the 288 cases reported, 280 were associated with importations from at least 18 countries, meaning they could have been the result of foreign nationals bringing it into the country, according to the findings of the CDC's latest Morbidity and Mortality Weekly Report released Thursday. The total also included 40 cases where American residents brought back the disease after traveling abroad.
An estimated 90% of U.S. cases were in those who were either unvaccinated or whose vaccination status could not be determined. Of that number, 165 were said to have refused vaccination because of religious, philosophical or personal objections, accounting for 57% of all cases.
“Measles in the U.S. has reached a 20-year high,” said Dr. Anne Schuchat, director of the CDC's National Center for Immunizations and Respiratory Diseases in a call with reporters. “This is not the kind of record we want to break, but should be a wake-up call for travelers and parents to make sure vaccinations are up to date.”
Measles was officially declared “eliminated” within the U.S. in 2000, but since that time the annual number of cases has varied, reaching a low of 37 in 2004 to a high of 220 in 2011.
The increase in the number of measles cases did not appear to indicate a national upward trend in the number of those who chose not to vaccinate, Schuchat said. The current outbreak does not appear related to concerns first expressed back in 1990s when a paper that appeared in the Lancet in 1998 alleged the measles, mumps and rubella vaccine had a causal link to an onset of autism spectrum disorders, Schuchat said.
The paper has since been discredited and was retracted by the medical journal in 2010 after discovering the study's author, Dr. Andrew Wakefield, had used false data to reach his conclusions.
Globally, measles remains one of the most contagious diseases, infecting an estimated 20 million people annually and leading to more than 120,000 deaths a year, according to the CDC.
Follow Steven Ross Johnson on Twitter: @MHsjohnson
