Doctors and public health officials are girding for the possible arrival of measles in Massachusetts, as an outbreak that originated in California’s Disneyland moves swiftly across the country and sparks renewed alarm over a nearly conquered illness.
State and city public health authorities have circulated alerts urging health workers, many of whom have never treated a case of measles, to be vigilant for its symptoms (fever, cough, runny nose, red eyes, and rash) and to isolate any patient who may have the virus.
“I think we’re all worried,” said Dr. Lawrence Madoff, director of the epidemiology and immunization division at the state Department of Public Health. “It would not surprise me to see a case in Massachusetts.”
The Disneyland outbreak has sickened 102 people, including one in New York, which borders Massachusetts, and seven in Arizona, where the Super Bowl was held last weekend.
The outbreak has raised widespread concerns because people from all over the country and the world visit the Southern California amusement park, extending the virus’s potential spread at a time when an increasing number of people are shunning the measles vaccine.
While immunization rates remain high in Massachusetts, cases of the disease occur almost every year in the state. The virus typically arrives from abroad, carried by a traveler from a nation where the disease is endemic. Usually, just a few people are affected.
Most people who get measles recover fully and can’t get infected again. But the virus can lead to serious complications and even death: One person out of every 500 infected suffers long-lasting harm such as deafness, seizures, and brain damage. And one out of every 500 dies.
Because Massachusetts reports one of the nation’s highest rates of immunization against measles, any potential outbreak will be limited, Madoff said. The measles vaccine is one of the most effective there is, protecting all but 3 percent of those vaccinated. But in certain Massachusetts communities, clusters of people are resisting vaccinating their children, creating pockets of vulnerability where the virus could get a foothold.
And adults who received an earlier version of the measles vaccine, between 1963 and 1968, may not be fully protected, said Dr. Anita Barry, director of the infectious disease bureau at the Boston Public Health Commission. Those adults should get revaccinated.
Dr. Cody Meissner, chief of pediatric infectious diseases at Tufts Medical Center’s Floating Hospital for Children, noted that certain people cannot be immunized against measles, including infants, transplant recipients, people infected with HIV, and those undergoing chemotherapy. If exposed to measles, they are more likely to die, Meissner said.
The vulnerability of infants was highlighted Thursday, when Illinois health officials reported that five babies — too young for vaccination — were diagnosed with measles at a suburban Chicago day care center, and 10 others were possibly exposed. There is no known link to the Disneyland outbreak, however.
Measles remains a worry because of “its extraordinary ability to infect people,” said Dr. Elizabeth D. Barnett, a pediatric infectious disease specialist at Boston Medical Center. “It’s one of the most highly contagious viruses that we know about.”
A person can catch measles by walking into a room in which an infected person sneezed two hours earlier. Just as concerning: People carrying the virus can spread it for four days before the tell-tale rash appears and four days after it ends, meaning people who seem well can make others sick.
Before the measles vaccine was licensed in 1963, about 3 million to 4 million people got infected each year in the United States, 400 to 500 died, and 48,000 were hospitalized. In 2000, the United States declared that measles was eliminated from this country, meaning that the disease is no longer constantly present.
But measles is common in other countries, and outbreaks occur when someone from abroad comes in contact with unvaccinated Americans. These outbreaks have been getting bigger and more frequent as vaccination rates have fallen in some communities, driven by unproven notions about vaccine side effects. As a result, 644 cases of measles were diagnosed in 27 states last year, the most in more than 20 years.
Eight of those cases were in Massachusetts. One was a man from Germany who came to Massachusetts General Hospital, recalled Dr. David C. Hooper, chief of the hospital’s infection control unit. The staff recognized the illness and isolated the patient quickly to prevent the virus from escaping.
The hospital then had to make sure that everyone who came in contact with the man had documented immunity to measles. “These sorts of things can generate a lot of work, to make sure you don’t miss anybody who might have been susceptible,” Hooper said.
There was only one measles case in Massachusetts in 2013, none in 2012, and 24 in 2011.
The most severe Massachusetts outbreak of recent years occurred in 2006, when a computer programmer from India spread measles to coworkers at the John Hancock tower who then infected others. Eventually, 15 people fell ill in that single outbreak, and public health officials spent weeks locating everyone who had come in contact with the sick people, checking their immunization status, offering vaccines, and quarantining more than 1,000 people.
To achieve “herd immunity” against measles — the condition in which so many people are vaccinated that the whole community is protected — 95 percent of a population needs to be immune.
In 2013, Massachusetts had the fourth-highest percentage (95.8 percent) of children age 19 months to 35 months who had received the measles-mumps-rubella vaccine.
But there is variability within the state. Although state law requires vaccination before children can attend school, parents may obtain an exemption by providing a medical reason or merely stating they have a religious objection. The number who obtained exemptions increased from less than 1 percent in the 2000-2001 school year to 1.5 percent in 2013-14.
In certain parts of the state, exemption rates are much higher: 5.5 percent in Franklin County and 4.9 percent on Cape Cod, Nantucket, and Martha’s Vinyard.
“Whenever vaccination starts to drop, we do have the risk of relatively large outbreaks,” said William P. Hanage, associate professor of epidemiology at the Harvard School of Public Health. “Once you start getting to numbers of 500 or 1,000, we will start seeing deaths.”
But there are still so many people in the country who are immune to measles that the disease is unlikely to make a full comeback, he said.