Measles is caused by a single-stranded, enveloped RNA virus with 1 serotype. Measles infection is transmitted to humans by airborne route. Humans are the only natural hosts of measles virus.
Signs and Symptoms
Measles is an acute viral respiratory illness characterized by a prodrome of fever (as high as 105°F) and malaise, cough, coryza, and conjunctivitis. Two or three days after onset of symptoms, tiny white spots (Koplik spots) may appear inside the mouth.
In about 14 days after exposure to the Measles virus, a rash breaks out and spreads from the head to the trunk to the lower extremities. Patients are considered to be contagious from 4 days before to 4 days after the rash appears. Of note, sometimes immunocompromised patients do not develop the rash.
People at high Risk for Complications Due to Infection
- Infants and children aged
- Adults aged >20 years
- Pregnant women
- People with compromised immune systems, such as from leukemia and HIV infection
Measles is one of the most contagious of all infectious diseases; up to 9 out of 10 susceptible persons with close contact to a measles patient will develop measles. The virus is transmitted by direct contact with infectious droplets or by airborne spread when an infected person breathes, coughs, or sneezes. Measles virus can remain infectious in the air for up to two hours after an infected person leaves an area.
Diagnosis and Laboratory Testing
Laboratory confirmation is essential for all sporadic measles cases and all outbreaks. Detection of measles-specific IgM antibody in serum and measles RNA by real-time polymerase chain reaction (RT-PCR) in a respiratory specimen are the most common methods for confirming measles infection. Urine samples may also contain virus, and when feasible to do so, collecting both respiratory and urine samples can increase the likelihood of detecting measles virus.
Evidence of Immunity
Acceptable presumptive evidence of immunity against measles includes at least one of the following:
- written documentation of adequate vaccination:
- one or more doses of a measles-containing vaccine administered on or after the first birthday for preschool-age children and adults not at high risk
- two doses of measles-containing vaccine for school-age children and adults at high risk, including college students, healthcare personnel, and international travelers
- laboratory evidence of immunity
- laboratory confirmation of measles
- birth before 1957
CDC recommends routine childhood immunization for MMR vaccine starting with the first dose at 12 through 15 months of age, and the second dose at 4 through 6 years of age or at least 28 days following the first dose.
Students at post-high school educational institutions
Students at post-high school educational institutions without evidence of measles immunity need two doses of MMR vaccine, with the second dose administered no earlier than 28 days after the first dose.
People who are born during or after 1957 who do not have evidence of immunity against measles should get at least one dose of MMR vaccine.
People 6 months of age or older who will be traveling internationally should be protected against measles. Before traveling internationally,
- Infants 6 through 11 months of age should receive one dose of MMR vaccine†
- Children 12 months of age or older should have documentation of two doses of MMR vaccine (the first dose of MMR vaccine should be administered at age 12 months or older; the second dose no earlier than 28 days after the first dose)
- Teenagers and adults born during or after 1957 without evidence of immunity against measles should have documentation of two doses of MMR vaccine, with the second dose administered no earlier than 28 days after the first dose
Infants who get one dose of MMR vaccine before their first birthday should get two more doses according to the routinely recommended schedule (one dose at 12 through 15 months of age and another dose at 4 through 6 years of age or at least 28 days later).