Measles: Not just a childhood rash
ABSTRACTIn recent years, the number of US measles cases has increased, and outbreaks in adults continue to be reported in communities with a high number of unvaccinated people. These trends underscore the need for high overall measles vaccination coverage, and for physicians to entertain the diagnosis of measles in adult patients with a febrile illness and rash.
KEY POINTS
- Measles is one of the most contagious infectious diseases, with a secondary attack rate of at least 90% in susceptible household contacts.
- Since 1993, most reported cases of measles have been directly or indirectly linked to international travel, and many have occurred in adults.
- Acute measles encephalitis, a neurologic complication of measles, is more common in adults than in children and is characterized by the resurgence of fever during the convalescent phase, along with headaches, seizures, and altered consciousness.
MEASLES IN COMPROMISED IMMUNITY
Measles patients with deficiencies of cellmediated immunity have a prolonged, severe, and often fatal course.2,23,24 This includes patients with:
- Human immunodeficiency virus (HIV) infection
- Congenital immunodeficiencies
- Disorders requiring chemotherapeutic and immunosuppressive therapy.
These patients are particularly susceptible to acute progressive encephalitis and measles pneumonitis. Case-fatality rates of 70% in cancer patients and 40% in HIV-infected patients have been reported.24
The diagnosis of measles may be difficult in patients without cell-mediated immunity, as 25% to 40% of them do not develop the characteristic rash.2,23 The absence of rash supports the theory that the rash is a hypersensitivity reaction to the virus.
MODIFIED AND ATYPICAL MEASLES
Modified measles
A modified form of measles can occur in people with some degree of passive immunity to the virus, including those previously vaccinated. It occurs mostly in patients who recently received immunoglobulin products, or in young infants who have residual maternal antibody. A modified measles illness can also follow vaccination with live-virus vaccine (see later discussion).
The clinical manifestations vary, and the illness may not have the classic features of prodrome, rash, and Koplik spots.
Atypical measles
Atypical measles is an unusual form that can occur when a person previously vaccinated with a killed-virus measles vaccine (used from 1963 to 1967) is exposed to wild-type measles.25 Features include a shorter prodrome (1 to 2 days), followed by appearance of a rash that begins on the distal extremities and spreads centripetally, usually sparing the neck, face, and head. The rash may be petechial, maculopapular, urticarial, vesicular, or a combination. The rash is accompanied by high fever and edema of the extremities. Complications such as pneumonia and hepatitis may occur.
The course of atypical measles is more prolonged than with classic measles, but because these patients are thought to have partial protection against the virus, they do not transmit it and are not considered contagious.26
DIAGNOSIS OF MEASLES
The classic clinical features are usually enough to distinguish measles from other febrile illnesses with similar clinical manifestions, such as rubella, dengue, parvovirus B19 infection, erythema multiforme, Stevens-Johnson syndrome, and streptococcal scarlet fever. The distinctive measles prodrome, Koplik spots, the progression of the rash from the head and neck to the trunk and the extremities, and the severity of disease are distinctive features of measles.
Laboratory tests to confirm the diagnosis are often used in areas where measles is rare, and laboratory confirmation is currently recommended in the United States. Because viral isolation is technically difficult and is not widely available, serologic testing is the method most commonly used. The measles-specific immunoglobulin M (IgM) antibody assay, the test used most often, is almost 100% sensitive when done 2 to 3 days after the onset of the rash.27,28 Measles IgM antibody peaks at 4 weeks after the infection and disappears by 6 to 8 weeks.
It is important to remember that false-positive measles IgM antibody may occur with other viral infections, such as parvovirus B19 and rubella. Because measles-specific IgG antibody is produced with the onset of infection and peaks at 4 weeks, a fourfold rise in the IgG titer is useful in confirming the diagnosis. Measles IgG antibody after infection is sustained for life.
Reverse transcription-polymerase chain reaction testing can also detect measles virus in the blood and urine when direct evidence of the virus is necessary, such as in immunocompromised patients.29
TREATMENT IS SUPPORTIVE
Treatment of measles mainly involves supportive measures, such as fluids and antipyretics. Antiviral agents such as ribavirin and interferon have in vitro activity against the measles virus and have been used to treat severe measles infection in immunocompromised patients. However, their clinical efficacy is unproven.30
Routine use of antibacterial agents to prevent secondary bacterial infection is not recommended.
CURRENT RECOMMENDATIONS FOR ACTIVE IMMUNIZATION
Active immunization for measles has been available since 1963. Between 1963 and 1967, both killed-virus and live-virus vaccines were available. As atypical measles cases became recognized, the killed-virus vaccine was withdrawn.
The vaccine currently available in the United States is a live-attenuated strain prepared in chicken embryo cell culture and combined with mumps and rubella vaccine (MMR) or mumps, rubella, and varicella vaccine (MMRV).
Two doses of live-virus measles vaccine are recommended for all healthy children before they begin school, with the first dose given at 12 to 15 months of age. A second dose is needed because the failure rate with one dose is 5%. More than 99% of people who receive two doses separated by 4 weeks develop serologic evidence of measles.
Waning immunity after vaccination occurs very rarely, with approximately 5% of children developing secondary vaccine failure 10 to 15 years after vaccination.3,31
Although rates of vaccination in the United States are high, cases of measles continue to occur in unvaccinated infants and in children who are either too young to be vaccinated or whose parents claimed exemption because of religious or personal beliefs.
Because of the occurrence of measles cases in adolescents, young adults, and adults, potentially susceptible people should be identified and vaccinated according to current guidelines. People should be considered susceptible unless they have documentation of at least two doses of measles vaccine given at least 28 days apart, physician-diagnosed measles, laboratory evidence of immunity to measles, or were born before 1957. All adults who are susceptible should receive at least one dose of measles vaccine.10 Adults at higher risk of contracting measles include:
- Students in high school and college
- International travelers
- Health care personnel.
For these adults, two doses of measles vaccine, at least 28 days apart, are recommended.32
Postexposure prophylaxis
Measles vaccination given to susceptible contacts within 72 hours of exposure as postexposure prophylaxis may protect against infection and induces protection against subsequent exposures to measles.33,34 Vaccination is the intervention of choice for susceptible individuals older than 12 months of age who are exposed to measles and who do not have a contraindication to measles vaccination.35 Active rather than passive immunization is also the strategy of choice for controlling measles outbreaks.
Passive immunization with intramuscular immune globulin within 6 days of exposure can be used in selected circumstances to prevent transmission or to modify the clinical course of the infection.36 Immune globulin therapy is recommended for susceptible individuals who are exposed to measles and who are at high risk of developing severe or fatal measles. This includes individuals who are being treated with immunosuppressive agents, those with HIV infection, pregnant women, and infants less than 1 year of age. Immune globulin should not be used to control measles outbreaks.
