Measles (Rubeola)

INFECTIOUS AGENT Measles virus is a member of the genus Morbillivirus of the family Paramyxoviridae. Humans are the only known natural host for the measles virus. Measles is one of the most highly communicable infectious diseases. MODE OF TRANSMISSION Measles virus spreads by airborne droplets or by direct contact with nasal or throat secretions of infected people. It is less commonly spread by articles freshly soiled with nose and throat secretions. Infected people are usually contagious from 4 days before until 4 days after the onset of signs or symptoms. EPIDEMIOLOGY The number of reported measles cases in the United States has declined from nearly 900,000 per year in the early 1940s to fewer than 150 cases annually since 1997. As a result of high vaccination coverage, in 2000 measles was declared eliminated in the United States. Indigenous measles virus circulation was interrupted in 2002 in the rest of the Western Hemisphere. However, measles virus continues to be imported into the United States from other parts of the world. Globally, an estimated 20 million measles cases occur each year. Given the large global incidence and high communicability of the disease, travelers may be exposed to the virus in almost any country they visit, but the risks are higher in countries where measles is endemic or where large outbreaks are occurring. Of the 67 reported measles cases in the United States in 2009, 13 occurred among US residents who were traveling abroad (4 people became infected in the United Kingdom, 4 in India, 2 in China, and 1 each in Cape Verde, the Philippines, and Vietnam), and 5 cases occurred among foreign visitors to the United States (from the United Kingdom, France, Italy, South Africa, and India). People who do not have evidence of measles immunity should be considered at risk for measles during international travel. Acceptable presumptive evidence of immunity to measles for international travelers includes meeting one or more of the following criteria: For infants aged 611 months, documented administration of 1 dose of live measlescontaining vaccine (MCV) and for people aged 12 months, 2 doses of MCV 28 days apart, on or after the first birthday Laboratory evidence of immunity Birth before 1957 Documented physician-diagnosed measles CLINICAL PRESENTATION The incubation period is about 10 days (range, 718 days) from exposure to onset of fever, usually 14 days before appearance of rash. Symptoms include prodromal fever, conjunctivitis, coryza (runny nose), cough, and small spots with white or bluish-white centers on an erythematous base on the buccal mucosa (Koplik spots). Characteristic red, blotchy (maculopapular) rash appears on the third to seventh day; it begins on the face, becomes generalized, and lasts 47 days. Common complications include diarrhea (8%), middle ear infection (7%9%), and pneumonia (1%6%). Encephalitis, frequently resulting in permanent brain damage, occurs in approximately 1 per 1,0002,000 cases of measles. Subacute sclerosing panencephalitis (SSPE), a rare but serious degenerative

central nervous system disease, is thought to occur in 1 per 100,000 cases, although a rate of 22 SSPE cases per 100,000 measles cases was found during the 19891991 measles resurgence in the United States. SSPE, which is caused by a persistent infection with a defective measles virus, is manifested by mental and motor deterioration that starts an average of 7 years after measles virus infection (most frequently in children who were infected at age <2 years), progressing to coma and death. The risk of serious complications and death is highest for children aged 5 years and adults aged 20 years. It is also higher in populations with poor nutritional status. DIAGNOSIS A clinical case of measles illness is characterized by all of the following: Generalized maculopapular rash lasting 3 days Temperature of 101F (38.3C) Cough, coryza, or conjunctivitis Laboratory criteria for diagnosis include any of the following: a positive serologic test for measles IgM, seroconversion, a significant rise in measles IgG level by any standard serologic assay, isolation of measles virus, or identification by PCR of measles virus RNA from a clinical specimen. A confirmed case is one that is either laboratory-confirmed or that meets the clinical case definition and is epidemiologically linked to a confirmed case. A laboratory-confirmed case does not need to meet the clinical case definition. TREATMENT Treatment is supportive. The World Health Organization recommends vitamin A for all children with acute measles, regardless of their country of residence, to reduce the risk of complications. Vitamin A is administered once a day for 2 days at the following doses: 50,000 IU for infants aged <6 months 100,000 IU for infants aged 611 months 200,000 IU for children aged 12 months A third, age-specific dose of vitamin A is to be given 24 weeks later to patients with clinical signs and symptoms of vitamin A deficiency. Parenteral and oral formulations of vitamin A are available in the United States. PREVENTIVE MEASURES FOR TRAVELERS Vaccine People traveling abroad, including people traveling to industrialized countries, who do not have evidence of measles immunity should be up to date on their MCV vaccination before departure. Measles vaccine contains live, attenuated measles virus. In the United States, it is available only in combination formulations, such as measles-mumps-rubella (MMR) and measles-mumps-rubella-varicella (MMRV). MMRV vaccine is licensed for children aged 12 months to 12 years and may be used in place of MMR vaccine if vaccination for measles, mumps, rubella, and varicella is needed. However, compared with use of separate MMR and varicella vaccines at the same visit, use of MMRV vaccine is associated with a higher risk for fever and febrile seizures. Most international travelers should receive 1 or 2 doses before travel: Infants aged 611 months should have at least 1 MCV dose. Infants vaccinated before age 12 months must be revaccinated on or after the first birthday with 2 doses of MCV separated by 28 days. MMRV is not licensed for children aged <12 months. Preschool children aged 12 months should have 2 MCV doses separated by 28 days. School-age children should have 2 MCV doses separated by 28 days.

Adults born in or after 1957 should have 2 MCV doses separated by 28 days. If administered at 12 months of age, 1 dose of MCV or MMR is 95% effective in preventing measles disease, and 2 doses are 99% effective. One dose of MCV or MMR is approximately 85% effective if administered at 9 months of age. MCV and immune globulin (IG) are effective as postexposure prophylaxis. MCV, if administered within 72 hours after initial exposure, may provide some protection. If the exposure does not result in infection, the vaccine should induce protection against subsequent measles virus infection. IG can be used to prevent or mitigate measles in a susceptible person when administered within 6 days of exposure. However, any immunity conferred is temporary unless modified or typical measles occurs, and the person should receive MCV 56 months after IG administration. Vaccine Safety and Adverse Reactions In rare circumstances, MMR vaccination has been associated with the following adverse events: Anaphylaxis (approximately 13.5 occurrences per million doses administered) Thrombocytopenia (a rate of 1 case in every 25,000 doses during the 6 weeks after immunization) Febrile seizures (The risk of febrile seizures increases approximately 3-fold 814 days after receipt of MMR vaccine, but overall, the rate of febrile seizure after MCV is much lower than the rate after measles disease.) Acute arthritis (Arthralgia develops among approximately 25% of susceptible postpubertal females after MMR vaccination, and approximately 10% have acute arthritislike signs and symptoms.) Joint symptoms (If they occur, they generally persist for 1 day to 3 weeks and rarely recur. Chronic joint symptoms attributable to the rubella component of the MMR vaccine are rare, if they occur at all.) Evidence does not support a link between MMR vaccination and any of the following: hearing loss, retinopathy, optic neuritis, ocular palsies, Guillain-Barr syndrome, cerebellar ataxia, Crohn disease, or autism. A published report on MMR vaccination and inflammatory bowel disease and pervasive developmental disorders (such as autism) has never been replicated by other studies and has subsequently been retracted by the journal. Compared with use of MMR and varicella vaccines at the same visit, use of MMRV vaccine is associated with a higher risk for fever and febrile seizures 512 days after the first dose among children aged 1223 months (about 1 extra febrile seizure for every 2,3002,600 MMRV vaccine doses). Use of separate MMR and varicella vaccines avoids this increased risk for fever and febrile seizures. Precautions and Contraindications Allergy People with severe allergy (hives, swelling of the mouth or throat, difficulty breathing, hypotension, and shock) to gelatin or neomycin, or who have had a severe allergic reaction to a prior dose of MMR or MMRV, should not be revaccinated, except with extreme caution. MMR or MMRV vaccines may be administered to people who are allergic to eggs without prior routine skin testing or the use of special protocols. Immunosuppression Enhanced replication of vaccine viruses can occur in people who have immune deficiency disorders. Death related to vaccine-associated measles virus infection has been reported among severely immunocompromised people. Therefore, severely immunosuppressed

people should not be vaccinated with MMR or MMRV vaccines (see Chapter 8 for a thorough discussion of recommendations for immunocompromised travelers): People who have received high-dose corticosteroid therapy (in general considered to be >20 mg prednisone or equivalent) daily or on alternate days for an interval of 4 days should avoid vaccination with MMR or MMRV for 1 month after cessation of steroid therapy. People who have received high-dose corticosteroid therapy daily or on alternate days for an interval of <14 days generally can be vaccinated with MMR or MMRV immediately after cessation of treatment, although some experts prefer waiting until 2 weeks after completion of therapy. Other immunosuppressive therapy: in general, MMR or MMRV vaccines should be withheld for 3 months after cessation of the immunosuppressive therapy and remission of the underlying disease. This interval is based on the assumptions that the immune response will have been restored in 3 months and the underlying disease for which the therapy was given remains in remission. Thrombocytopenia The benefits of primary immunization are usually greater than the potential risks of thrombocytopenia. However, avoiding a subsequent dose of MMR or MMRV vaccine may be prudent if an episode of thrombocytopenia occurred within approximately 6 weeks after a previous dose of vaccine.