By Chris Aldridge, MSW, Senior Director, Infectious Disease, NACCHO; and Matt Zahn, MD, Medical Director, Epidemiology, Orange County Health Care Agency
Author’s note: This article was originally published in NACCHO Exchange before the recent measles outbreak emerged at Disneyland in December 2014. The article has been edited from its original publication to reflect this news.
The United States has recently seen a resurgence in measles disease. This is due in part to misinformation about the safety of vaccines in general and the measles, mumps, and rubella (MMR) vaccine in particular. The resulting vaccine hesitancy has led to lower immunization rates, with individuals at higher risk of disease and populations at higher risk of outbreaks. Measles is a highly infectious disease caused by the measles virus, characterized by a flu-like illness followed by a characteristic rash. The first measles vaccine was developed in 1963 and the vaccine is now part of a combination vaccine that protects against MMR and varicella. As a result of vaccination, ongoing measles transmission was declared eliminated in the United States in 2000.
However, cases of measles continue to be imported, and transmission of the virus continues to occur, especially within unvaccinated populations. Between 2000 and 2013, U.S. measles case rates have ranged from 37 to 220 people per year, but in 2014 and 2015, the United States saw a significant resurgence. From Jan. 1 to Feb. 6, 2015, 121 people from 17 states and Washington D.C. were reported to have measles, with the majority of these cases related to an ongoing multistate outbreak linked to an amusement park in California.
This article discusses two recent outbreaks of measles in the United States. One occurred in the Amish community in Ohio, a community where little to no vaccinations had occurred. The other occurred in Orange County, CA, in a community that was relatively well vaccinated.
In spring 2014, a group of Amish missionaries returned to Ohio from the Philippines. The group was unaware of the severe measles outbreak occurring in the Philippines. Members of the group began showing illness on March 24, 2014. One individual was misdiagnosed as having dengue fever. Easter weekend saw the onset of the rash and official diagnosis of measles. The Easter holiday represents a time for family and friends to gather, increasing the likelihood for the disease to spread throughout the community. By the time the outbreak was declared over on Sept. 4, 2014, the outbreak included 377 cases, with nine hospitalizations, over nine counties. No deaths were reported due to the outbreak.
The Amish live in primarily rural areas of Ohio. Overall, their culture shuns technology, preferring to live simply. High school graduation rates are high within the community, although college graduation remains low. Small businesses within the community focus on woodworking, food, and tourism. The Amish community had very low rates of vaccination. Although some members of the community held strongly negative views of vaccinations, nothing specifically within the Amish culture opposed vaccinations. The main reasons for low vaccinations are misconceptions related to safety and need.
Because of the widespread nature of the outbreak, coordination across the nine counties was critical. The counties implemented an emergency management infrastructure to ensure common messaging and centralized communications. While each county planned its own vaccination clinics, the emergency management infrastructure ensured close coordination. The Ohio Department of Health provided support, but the response was mainly driven among the local counties. The Centers for Disease Control and Prevention sent a team to support case investigation and advise the health departments.
Because the Amish shun technology, mass media such as television was not an appropriate vehicle to share information. Instead, local health departments used over 300 regular mailings to bishops and daily free newspapers to reach the community, which then spread information very quickly. One key message was the economic impact the measles has if employees become sick and a business is forced to close temporarily. To remove barriers to vaccinations, health departments set up clinics to ensure ease of access to the Amish community. In Holmes County, a total of 5,300 vaccinations were given.
Personal communication worked well in the response. With mass media of little use, the health departments’ use of direct mailings and outreach to the community quickly spread the word about the disease and the time and location of vaccination clinics. An important lesson learned was that, to reach the community effectively, one did not necessarily need individuals from that community to communicate the message. The Amish community was very receptive to messages from public health officials if the messenger showed understanding and respect for the Amish community and its focus on family and faith. Having existing relationships prior to an event was also important for success. Established connections allowed health officials to respond more quickly and spend less time finding points of contact.
Orange County, CA, Outbreak
In Orange County, CA, 22 cases of measles were identified from Jan. 1 through March 30, 2014. Case ages ranged from 3-45 and were evenly split between males and females. Six persons were hospitalized, although none developed sequelae such as pneumonia or central nervous system disease. No deaths were reported. Seven cases were primary (without known exposure to another Orange County case), while 15 were secondary. Five cases occurred among healthcare workers. Ten had previous evidence of immunity, either by two documented doses of MMR or serologic measles IgG positive prior to developing illness.
The outbreak persisted for five generations. Initial cases included unvaccinated children and primary adult cases, with parents and healthcare workers caring for cases affected later in the outbreak.
This outbreak did not originate from a single index case but instead consisted of two community clusters. One cluster of five primary and five secondary cases centered on Hispanic adults living in North Orange County. Three family members of primary cases and two healthcare workers were secondarily infected. All cases that were typed had B3 infection, which is predominantly seen in the Philippines. No common source was identified, but the most likely scenario for this cluster was an initial traveler who came from the Philippines at the beginning of 2014, developed illness, and unwittingly exposed multiple persons in the community. The second cluster of disease centered on a pediatric population in South Orange County. An initial 16-year-old that was not vaccinated developed the disease, with subsequent infection of 10 secondary cases, including four children, three parents, and three healthcare workers.
A total of 2,245 community exposures occurred, including 1,994 (88%) persons identified to be exposed in a healthcare setting. Five healthcare workers eventually developed disease. Four of these five had face-to-face contact with a measles case. Four of the five healthcare workers who developed disease post-exposure were considered to be immune and thus not at risk of developing disease, based on serologic evidence of immunity or two documented doses of MMR, or both. The four healthcare workers who had initial evidence of immunity continued to work despite developing symptoms, resulting in hundreds of additional exposures in healthcare settings.
A total of 1,148 attempted phone contacts were made to persons exposed in a healthcare setting; several hundred more received letters. All of those contacted by phone were surveyed for evidence of immunity by questionnaire. Those who did not demonstrate evidence of immunity by interview were recommended to receive serologic testing. Of 263 tested due to exposure and insufficient proof of immunity, nine were found to be non-immune. Only one patient developed disease after exposure to a case in a waiting room environment. This case had previously received two MMR doses, and so was judged by the survey to be immune.
This outbreak has led to modification in Orange County Public Health’s measles response in multiple ways:
- In a community with a high immunization rate, aggressive search for evidence of immunity in persons with low-risk exposure, in particular non-face-to-face exposure in a healthcare setting exposure, is of low utility. Surveying and subsequent serologic testing to assess need for immunity and need for vaccination or immune globulin is not an efficient use of resources. Most persons will prove to be immune, and the number of secondary cases in this group will be very low. Orange County proposes that simply contacting these low-risk exposures to inform them of the exposure and encouraging them to follow up with a provider if symptomatic is adequate.
- The nature of exposure is a better indication of risk of illness than immune status. In future events, Orange County plans to remind all healthcare workers who have had close exposure to measles to follow up for testing and remove themselves from work with any symptoms and to encourage infection control officers at hospitals to remind these persons to watch for and report any symptoms.
- Healthcare workers who are exposed need to be educated about the nature of measles disease: respiratory illness with or without fever is the initial manifestation. Those with respiratory illness should stop working and present immediately for testing. Persons who wait for rash to develop may expose many patients and their families in the meantime.
- The incubation period for measles ranges from five to 21 days, and the response was based on this broad time range. However, most persons who had a single identified exposure developed initial symptoms eight to 12 days later, which mirrors the experience described in many measles studies. Future response will emphasize enhanced surveillance of those with significant exposure during this time period.
The distinct circumstances surrounding these outbreaks demonstrate the importance of a layered approach toward protecting people against measles. While vaccination continues to be the most important strategy, adequately communicating, educating, and ensuring healthcare and public infection control are also critical actions local health departments can take to prevent the emergence and spread of this disease.
This article was originally published in NACCHO Exchange. To read the entire issue, download the newsletter from NACCHO’s online bookstore. (Login required).
- Staff. “Work by Enders brings measles vaccine license.” The Hartford Courant, March 22, 1963. Available at http://bit.ly/13rpYSm
- The College of Physicians of Philadelphia. (2014). The history of vaccines: Measles. Available at http://www.historyofvaccines.org/content/timelines/measles
- Centers for Disease Control and Prevention. (2014). Frequently asked questions about measles in the U.S. webpage. Available at http://www.cdc.gov/measles/about/faqs.html
- Centers for Disease Control and Prevention. (2014). Measles cases and outbreaks webpage. Available at http://www.cdc.gov/measles/cases-outbreaks.html