By Betsy Todd, MPH, RN, CIC, AJN clinical editor
While debates about measles vaccination swirl around the current U.S. measles outbreak, most U.S. nurses have never actually seen the disease itself, and right now we are a lot more likely to encounter a case of measles than of Ebola virus disease. Here, then, is a measles primer.
Symptoms. Measles is an upper-respiratory infection with initial symptoms of fever, cough, runny nose, red and teary eyes, and (just before the rash appears) “Koplik spots” (tiny blue/white spots) on a reddened buccal mucosa. The maculopapular rash emerges a few days after these first symptoms appear (about 14 days after exposure), beginning at the hairline and slowly working its way down the rest of the body.
Infected people who are severely immunosuppressed may not have any rash at all. “Modified” measles, with a longer incubation period and sparse rash, can occur in infants who are partially protected by maternal antibodies and in people who receive immune globulin after exposure to measles.
Transmission. The virus spreads via respiratory droplets and aerosols, from the time symptoms begin until three to four days after the rash appears. (People who are immunosuppressed can shed virus and remain contagious for several weeks.) Measles is highly contagious, and more than 90% of exposed, nonimmune people will contract the disease. There is no known asymptomatic carrier state, and no nonhuman animal is known to carry or spread the virus. The virus survives for less than two hours in the air or on surfaces, and is rapidly inactivated by heat, light, acids, and disinfectants.
Isolation. When measles is suspected, airborne isolation is necessary. If negative pressure is not available, the patient should be placed in a room with the door closed. Only immune staff wearing N-95 masks should enter the room.
Diagnosis. The usual test for measles is serologic testing for immunoglobulin M (IgM) antibody; a positive test confirms the diagnosis. IgM is often evident as soon as the rash appears, and can be detected for about a month. A negative IgM test on a specimen taken within 72 hours of rash onset may be a false negative; the test should be repeated.
Measles virus can be cultured from a nasopharyngeal aspirate, throat swab, urine sample, or heparinized blood, but only specialized labs can perform these cultures and results are not available for several days. While cultures therefore do not provide a quick diagnosis, molecular testing can be done on culture isolates, and this is epidemiologically important during an outbreak.
Exposures. Measles vaccine given to a nonimmune person within 72 hours of exposure, or immune globulin given within six days of exposure, may prevent or modify infection. Whether or not postexposure prophylaxis is used, the exposed nonimmune person should be excluded from school, child care, or health care/child care work from five days after their first date of measles exposure through 21 days after their last date of exposure.
Complications. Complications are most common in children under five or adults older than 20. Diarrhea, otitis media, or pneumonia occur in a small percentage of measles infections. Seizures (with or without fever) affect less than one percent of patients. Acute encephalitis occurs in about one of every thousand measles infections, and permanent neurological damage is possible. If nonimmune pregnant women contract measles, there is an increased risk of premature labor, spontaneous abortion, and low-birthweight babies. In developed countries, there are about two deaths per 1,000 cases of measles.
You are considered immune to measles if you were born before 1957, have received two doses of live attenuated measles vaccine, had lab-confirmed measles infection, or have a detectable serum level of IgG measles antibody titer.
For links to excellent resources as well as the latest information about measles and about the current outbreak, visit the CDC Web site.