The 84 measles cases from 14 states reported to federal officials in January alone already exceed the total reported from some whole years, prompting a warning from the US Centers for Disease Control and Prevention (CDC) that Americans should be vaccinated and that clinicians be on guard for detecting and preventing the disease.
At a media briefing today, Anne Schuchat, MD, assistant surgeon general and director of the CDC's National Center for Immunization and Respiratory Diseases, said most of the cases are part of a multistate outbreak linked to a Disney theme park in California that started in late December. "This worries me," she said, airing concerns that a disease that was considered eliminated in the United States in 2000 is now at risk of becoming endemic again.
The surge in infections this month follows a banner year for the disease in 2014, during which more than 600 measles cases were reported in the United States, the most in 20 years.
Investigators aren't sure how the Disney-linked outbreak began, but they suspect someone contracted the disease overseas and brought the disease to the park, where they exposed others. The genotype linked to the Disney outbreak is circulating in 14 countries around the world.
Cases not linked to Disney so far this year have been linked to international travel to destinations such as Indonesia, Azerbaijan, and India. Schuchat said measles is a common disease in other countries, with about 20 million cases reported each year. According to global health estimates, about 122,000 people around the world die from the disease each year.
Adults among the hardest hit
One unique feature of this year's cases is that more adults have been affected, compared with a typical outbreak, she said. The median age of measles patients reported to the CDC this year is above 20 years.
So far, 15% of people with measles infections have been hospitalized, which is in line with what health officials typically see. She said it's too soon to tell if the clinical spectrum is different, given the larger portion of infected adults.
Most of the people infected in the latest outbreak weren't vaccinated or can't remember if they have been vaccinated. Schuchat said that although some infections have been reported in vaccinated people, the number isn't unexpected for a general population that has an overall high vaccination rate. So far there's no indication that there is a problem with the vaccine, but health officials are exploring all possibilities.
Schuchat urged people to vaccinate their children with the recommended two doses of measles, mumps, and rubella (MMR) vaccine, adding that the vaccine is very effective and has a good 50-year safety record. For adults who can't remember if they've been vaccinated, getting another isn't harmful, she said.
Measles can be a serious and sometimes fatal disease, especially for babies, some who are too young to be vaccinated, and people with underlying medical conditions who can't be vaccinated. Schuchat said the virus is highly contagious and that infected people can spread the disease even before they know they are sick and have a rash.
Part of the problem is that many Americans haven't seen measles before and don't know how bad the disease can be, she said. Though overall MMR vaccination levels are high and are improving, Schuchat said the disease can spread quickly in pockets of undervaccinated people.
Disney-linked cases growing
Schuchat said 67 of the cases reported to the CDC were part of the Disney outbreak—11 with illness onsets in December and 56 with onsets in January. She praised local and state health officials who are tracking the illnesses and tracing contacts.
Reports from state and local officials have put the number of Disney linked cases even higher. A story yesterday in the Los Angeles Times gives the total as 95, 79 of them in California. However, that story says five cases have occurred in Arizona, but the Arizona Department of Health Services (ADHS) as well as a story yesterday in USA Today list two new cases in Arizona that do not appear to be included in the California count.
The new Arizona cases are in two adults who had contact with a four-person unvaccinated family from the Kearny area in Pinal County that had visited Disneyland. The new case-patients are a man from Pinal County and a woman from Phoenix. The woman may have exposed as many as 195 children visiting the Phoenix Children's East Valley Center last week, says the USA Today story. The families of those children are being contacted.
Will Humble, director of the Arizona Department of Health Services (ADHS), is quoted in the article as saying the outbreak has reached "a critical point." In his director's blog yesterday, he said more than 1,000 contacts of the Pinal County family have been contacted over the past week.
Consulting editor Marty Swain contributed to this story.
Jan 28 LA Times story
Jan 28 USA Today article
Jan 28 ADHS blog entry