California health officials called for anyone who has not received the measles vaccine to get vaccinated as an outbreak of the disease continues to spread.
So far, at least 62 cases have been confirmed in California, as well as three in Utah, two in Washington, and one each in Colorado, Oregon, and Mexico. Of the California cases, 42 have been linked to Disneyland, and it's possible more people who have visited the park could get sick, officials told the AP.
"For the time being, if you are not vaccinated, or if you have an infant who is too young to be vaccinated, you should avoid going to Disneyland," said Dr. Gil Chavez of the California Department of Public Health.
A quarter of those who have contracted the disease have been hospitalized, he said, and infants, pregnant women, and anyone with a compromised immune system could face potentially deadly complications, such as pneumonia or encephalitis.
"People are really not aware of how dangerous this disease can be in children," he said.
Officials believe the first round of cases were tied to one sick person who visited Disneyland in mid-December. They had likely recently spent time in a country where the disease is common.
The highly contagious virus spread to other visitors to the theme park, as well as five Disneyland employees. Other people who were sick with measles also spent time at Disneyland in January.
The most recent confirmed case, on Jan. 18, was a Disneyland employee.
"Measles can be very contagious, even before there are symptoms," Chavez said.
Of the confirmed cases, most were intentionally unvaccinated, Chavez said. Six were children under the age of 1, too young to receive the vaccine.
For people who have received two doses of the vaccine, the standard since 1989, it is 99% effective, Chavez said. Most older Americans received one dose of the vaccine, which is 95% effective.
The vast majority of Californians have been immunized, but a growing minority of parents are choosing not to immunize their children. Chavez stressed that there is no evidence to back concerns that drive many parents to opt out of required childhood immunizations. He asked anyone who had not been vaccinated to reconsider, noting that the spread of outbreaks could prove fatal to those too young to receive their MMR shot.
"We have a particular responsibility to protect all of our infants in the state until they are old enough to be vaccinated," he said.
Measles, which is spread through the air, is one of the most contagious viruses in the world.
From one cough or sneeze, the virus can travel through the air for up to two hours and reach people up to 100 feet away. Once a person is exposed, it can take up to 21 days for them to become ill. Yet they are contagious four days before and four days after the onset of the rash that is the most visible sign of the disease.
Because a fever and cold-like symptoms typically begin before the telltale rash, most patients visit the doctor several times before they're diagnosed.
"This can easily amount to hundreds of contacts for each case," said Kathleen Harriman of California's health department.
Local health officials are working to identify everyone who may have come into contact with the disease, she said. But with something as contagious as measles, she added, that takes time.
In response to the outbreak, a school in Orange County has sent all unvaccinated students home. Disneyland has also asked some of its employees to provide immunization records or take a blood test to show they are immune, the Los Angeles Times reported. Vaccines are also being made available to employees who have not been immunized.
For anyone concerned about measles, health officials had a simple message: Get vaccinated. Otherwise, Chavez said, any visit to a theme park, airport, or other crowded place could be risky.
"Get immunized and then you don't have to worry about it," he said.