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It seems like Disneyland may not be the "happiest place on Earth" after all. A recent outbreak of measles has plagued the Southern California theme park. There are now fifty-nine confirmed measles cases directly or indirectly related to the original Disneyland outbreak. Measles is by no means a new virus and is highly preventable through vaccination. Why the sudden outbreak? A recent movement amongst parents to not vaccinate their children has decreased the effectiveness of "herd immunity." Loss of herd immunity puts more people at risk for becoming sick.
Health officials believe that tourists to Disneyland were initially exposed to measles between December 17th and December 20th. Of the six original cases, three were children and three were adults. All three children were old enough to have received the measles vaccination but were actually unvaccinated. Of the infected adults, one was fully vaccinated, one was partially vaccinated and one was unvaccinated. These original six people then spread the disease to others and so forth and so on. Patients as far away as Washington, Utah, Colorado, and Mexico have been diagnosed with measles stemming from direct or indirect contact with Disneyland. What's ironic about this Disneyland outbreak is that measles has been considered eliminated in the United States since the year 2000. However, measles has been making a comeback in the past few years due in part to the increasing numbers of unvaccinated individuals and increased global travel.
Measles was first documented in the 9th Century by a Persian doctor and is caused by the morbillivirus. The virus is generally spread between people through coughing and sneezing. Measles is extremely contagious. Ninety percent of people exposed to measles will contract the disease unless they have already been vaccinated or have had measles before. Until 1963, when the measles vaccination became available, almost all children contracted measles by the age of fifteen in the United States. Approximately three to four million people became infected with measles every year in the United States prior to vaccination. In 1954 scientists began collecting blood samples from Boston children sick with measles. The scientists were able to isolate the measles virus in the blood of a thirteen-year old boy, a necessary step in creating a vaccine. The scientists then released a vaccine in 1963 using the strain of measles identified in the boy's blood. A new and improved vaccine was released in 1968 and has since been the sole measles vaccine used in the United States.
Disneyland presents the perfect opportunity for measles to spread. People from all over the world converge into a relatively small area and come into close contact with each other. Tourists then travel back home via a plane or car further spreading any pathogens that they picked up while at Disneyland. Health officials are now trying to curb measles' spread by monitoring people who became sick or who may become sick with measles after coming into contact with Disneyland or infected individuals.
2014 marked the worst year for measles both nationwide and in California since measles was eliminated in the United States in 2000. Elimination means that measles is no longer native to the United States. Despite being eliminated, measles cases have popped up in recent years. As mentioned earlier, one reason for this is the increasing number of parents refraining from vaccinating their children. For example, in California more than 95% of kindergarteners in 2002 were fully vaccinated for measles and whooping cough while only 92% of current kindergarteners are fully vaccinated. Although a 3% drop may not seem significant, a vaccination percentage of 92% is"low enough to promote the spread of highly infectious diseases." Opponents of vaccination claim that the risks of vaccination outweigh the benefits of vaccination. In reality, the risks posed from contracting preventable diseases such as measles are far greater than the risks associated with vaccination. "You have a disease that can certainly cause hospitalization and death, and people play a very dangerous game when they choose not to vaccinate their children" explains Dr. Paul Offit, an expert in infectious diseases from the Children's Hospital of Philadelphia. Refraining from vaccination also hurts the immunity of the population as a whole. A population's immunity is based on the concept of "herd immunity." When the majority of a community is vaccinated, members are less likely to get sick since there is little chance of an outbreak. The phenomenon of herd immunity is especially vital to individuals medically unable to receive vaccination such as infants, pregnant women, and immunocompromised people. Although they themselves have not received vaccination their risk of becoming sick is significantly reduced because of the immunity of the population as a whole. To put it simply, greater immunity means less opportunity for transmission which translates to protection for individuals vulnerable to disease. There are more unvaccinated people in the U.S. currently then there has been in recent history. Health officials warn that if this trend continues then the number of cases of preventable diseases like measles will increase and thus jeopardize the health of the population.
The Disneyland outbreak is an unfortunate occurrence that should not have reached the magnitude it has. I hope though that this situation will bring to light the importance and necessity of vaccination.
Sources:
CDC. Q&A about Disease and Vaccine (2015).
The College of Physicians of Philadelphia. Measles (2015).
Vaccines.gov. Community Immunity (2015).
Photos:
Disneyland: Tuxyso (via Wikimedia Commons).
Infographic: National Institute of Allergy and Infectious Diseases (via Vaccines.gov).
