An 18-month-old boy, who is visiting family in San Antonio with his parents from Central America, presents with a 3-day history of fever, malaise, conjunctivitis, coryza, and cough. He had been exposed to a child with similar symptoms approximately 2 weeks prior. A day before, he developed a maculopapular rash that blanches under pressure (Figures 132-1 and 132-2). His shot records are unavailable, but his mother states that his last vaccine was before age 1 year. He is diagnosed with measles and supportive care is provided.
Typical measles rash that began on the face and became confluent. (Reproduced with permission from Richard P. Usatine, MD.)
The typical measles rash on the trunk. (Reproduced with permission from Richard P. Usatine, MD.)
Measles is a highly communicable, acute, viral illness that is still one the most serious infectious diseases in human history. Until the introduction of the measles vaccination, it was responsible for millions of deaths worldwide annually. Although the epidemiology of this disease makes eradication a possibility, the ease of transmission and the low percentage of nonimmunized population that is required for disease survival have made eradication of measles extremely difficult.
A major outbreak in the United States from 1989 to 1991 prompted changes in immunization policies which led to the initiation of two measles, mumps, rubella (MMR) vaccines administered prior to kindergarten.
This change in practice led to all-time lows in cases reported, and in 2000 the CDC declared that the United States had achieved measles elimination (defined as interruption of year-round endemic measles transmission).1
Despite the declaration of elimination, measles cases continue to be reported in the United States, with most cases being linked to incomplete vaccinations. In 2015, an outbreak was noted when 110 patients in California were diagnosed with measles in association with a theme park. Of those patients, 45% were unvaccinated, 43% had unknown or undocumented vaccination status, and 5% had only one dose of measles-containing vaccination.2 Among 37 vaccine-eligible patients, 28 (76%) were intentionally unvaccinated because of personal beliefs.2
The worldwide incidence of measles was reduced from 280,525 cases in 2014 to 195,762 in 2015 according to WHO Global and Regional Immunization Profile. In 2015, approximately 85% of the world's target population received one dose of measles vaccine, up from 84% in 2014, and 61% received 2 doses, up from 58% in 2014.3
ETIOLOGY AND PATHOPHYSIOLOGY
Measles is caused by the measles virus, a member of the family Paramyxoviridae, genus Morbillivirus (hence the name morbilliform rash).
It is highly contagious, is transmitted by airborne droplets, and commonly causes outbreaks....