- An exanthematous disease that has a relatively predictable course, making clinical diagnosis possible
- Because it is rare, cases are often initially misdiagnosed as a nonspecific viral exanthema, drug eruption, or Kawasaki disease.
- Types of measles include the following:
- Typical measles (outlined below)
- Modified measles
- A mild form of measles can occur in children with passive immunity to the virus.
- This setting includes babies with maternal-acquired antibody and children who have received immune globulin.
- Some of the classic symptoms and signs may be absent.
- Measles is one of the most highly contagious of all infectious diseases.
- Patients are contagious from 1 to 2 days before onset of symptoms (3 to 5 days before rash) until 5 days after the appearance of the rash. The incubation period is generally 8 to 12 days from exposure to onset of symptoms and ~14 days until the appearance of rash.
- Hospital or clinic waiting rooms, especially pediatric emergency department waiting rooms, have been identified as a major risk, accounting for up to 45% of known exposures. With adequate immunization (2 doses = 99% effective), measles could be eliminated as a disease.
- Although no longer endemic in the United States, networks of intentionally unvaccinated children have led to several recent U.S. outbreaks originating from measles virus imported from abroad.
- Because 20 million cases of measles, resulting in 150,000 deaths, occur globally per year, it is critical to maintain high levels of vaccination coverage.
- Before the 1963 licensure of vaccine, an estimated 3 to 4 million people acquired measles in the United States each year, including 4,000 cases of encephalitis and 500 deaths; by 1983, there were only 0.7 cases per 100,000 population.
- Delays in immunization facilitated large outbreaks in the United States from 1989 to 1991, peaking in 1990 when 27,672 cases were reported, 89 of which were fatal.
- From 2001 to 2012, the median annual number of measles cases reported in United States was 60.
- From January to August 2013, 159 U.S. cases were reported, including the largest U.S. outbreak since 1996 (58 cases). The majority of cases occurred in underimmunized individuals and imported from abroad (including U.S. travelers).
- In 2014, 667 measles cases from 23 outbreaks occurred in the United States, including a single outbreak of 383 cases, primarily among unvaccinated Amish communities in Ohio.
- In 2015, a large, multistate measles outbreak was linked to an amusement park in California.
- Vaccine recommendations
- Routine vaccination against measles, mumps, and rubella (MMR) for children begins at 12 to 15 months of age, with a second MMR vaccination at age 4 to 6 years.
- With the recent resurgence of measles, aggressive employee immunization programs should be pursued for all health care workers.
- Health care workers born after 1956 who have no documentation of vaccination or evidence of measles immunity should be vaccinated at the time of employment and revaccinated ≥28 days later.
- Infection control measures
- Any inpatient suspected of having measles should be in a negative-pressure respiratory isolation room; health care workers must wear masks, gloves, and gowns (airborne and contact precautions).
- Isolation is required for 4 days after the first appearance of the rash; immunocompromised patients require isolation for the course of the illness.
- All suspected cases of measles should be reported immediately to the local health department.
Transmission of measles occurs through direct contact with infectious droplets, less commonly by airborne spread.
Measles is an RNA virus (paramyxovirus, genus Morbillivirus) with only one serotype.
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