Measles

Definition

Measles is an infection caused by a virus, which causes an illness displaying a characteristic skin rash known as an exanthem. Measles is also sometimes called rubeola, five-day measles, or hard measles.

Description

Measles is a very contagious disease primarily characterized by cough , runny nose, red eyes ( conjunctivitis ), and a characteristic rash on the skin and inside of the cheeks. The most common complications are ear infection and diarrhea , although more serious complications can include pneumonia , meningitis , or encephalitis . Measles is fatal (due to complications) in about two out of every 1,000 cases.

Demographics

Measles infections appear all over the world. Prior the effective immunization program used in the early 2000s, large-scale measles outbreaks occurred on a two to three-year cycle, usually in the winter and spring. Smaller outbreaks occurred during the off years. Babies up to about eight months of age are usually protected from contracting measles, due to immune cells they receive from their mothers in the uterus. Once someone has had measles infection, he or she can never get it again.

Causes and symptoms

Measles is caused by a type of virus called a paramyxovirus. It is an extremely contagious infection, spread through the tiny droplets that may spray into the air when an individual carrying the virus sneezes or coughs. About 85 percent of those people exposed to the virus will become infected with it. About 95 percent of those people infected with the virus will develop the illness called measles. Once someone is infected with the virus, it takes about seven to 18 days before he or she actually becomes ill. The most contagious time period is the three to five days before symptoms begin through about four days after the characteristic measles rash has begun to appear.

The first signs of measles infection are fever ; extremely runny nose; red, runny eyes; and a cough. A few days later, a rash appears in the mouth, particularly on the mucous membrane that lines the cheeks. This rash consists of tiny white dots (like grains of salt or sand) on a reddish bump. These are called Koplik's spots and are unique to measles infection. The throat becomes red, swollen, and sore.

A couple of days after the appearance of the Koplik's spots, the measles rash begins. It appears in a characteristic progression, from the head, face, and neck, to the trunk, then abdomen, and next out along the arms and legs. The rash starts out as flat, red patches but eventually develops some bumps. The rash may be somewhat itchy. When the rash begins to appear, the fever usually climbs higher, sometimes reaching as high as 105°F (40.5°C). There may be nausea , vomiting , diarrhea, and multiple swollen lymph nodes. The cough is usually more problematic at this point, and the patient feels awful. The rash usually lasts about five days. As it fades, it turns a brownish color and eventually the affected skin becomes dry and flaky.

Many patients (about 5–15%) develop other complications. Bacterial infections, such as ear infections, sinus infections, and pneumonia are common, especially in children. Other viral infections may also strike the patient, including croup , bronchitis , laryngitis, or viral pneumonia. Inflammation of the liver, appendix, intestine, or lymph nodes within the abdomen may cause other complications. Rarely, inflammations of the heart or kidneys, a drop in platelet count (causing episodes of difficult-to-control bleeding), or reactivation of an old tuberculosis infection can occur.

An extremely serious complication of measles infection is swelling of the brain. Called encephalitis, this condition can occur up to several weeks after the basic measles symptoms have resolved. About one out of every thousand patients develops this complication, and about 10 to 15 percent of these patients die. Symptoms include fever, headache , sleepiness, seizures, and coma. Long-term problems following recovery from measles encephalitis may include seizures and mental retardation .

A very rare complication of measles can occur up to ten years following the initial infection. Called subacute sclerosing panencephalitis, this is a slowly progressing, smoldering swelling and destruction of the entire brain. It is most common among people who had measles infection prior to the age of two years. Symptoms include changes in personality, decreased intelligence with accompanying school problems, decreased coordination, involuntary jerks and movements of the body. The disease progresses so that the individual becomes increasingly dependent, ultimately becoming bedridden and unaware of his or her surroundings. Blindness may develop, and the temperature may spike (rise rapidly) and fall unpredictably as the brain structures responsible for temperature regulation are affected. Death is inevitable.

Measles during pregnancy is a serious disease, leading to increased risk of a miscarriage or stillbirth. In addition, the mother's illness may progress to pneumonia.

Diagnosis

Measles infection is almost always diagnosed based on its characteristic symptoms, including Koplik's spots, and a rash which spreads from central body structures out towards the arms and legs. If there is any doubt as to the diagnosis, then a specimen of body fluids (mucus, urine) can be collected and combined with fluorescent-tagged measles virus antibodies. Antibodies are produced by the body's immune cells that can recognize and bind to markers (antigens) on the outside of specific organisms, in this case the measles virus. Once the fluorescent antibodies have attached themselves to the measles antigens in the specimen, the specimen can be viewed under a special microscope to verify the presence of measles virus.

Measles rash on a child's face.

(© CNRI/Photo Researchers, Inc.)

Treatment

As of 2004 there are no treatments available to stop measles infection. Treatment is primarily aimed at helping the patient to be as comfortable as possible and watching carefully so that antibiotics can be started promptly if a bacterial infection develops. Fever and discomfort can be treated with acetaminophen . Children with measles should never be given aspirin, as aspirin is correlated with the fatal disease Reye's syndrome . A cool-mist vaporizer may help decrease the cough. Patients should be given a lot of liquids to drink, in order to avoid dehydration from the fever.

Some studies have shown that children with measles encephalitis benefit from relatively large doses of vitamin A.

Prognosis

The prognosis for an otherwise healthy, well-nourished child who contracts measles is usually quite good. In developing countries, however, death rates may reach 15 to 25 percent. Adolescents and adults usually have a more difficult course. Women who contract the disease while pregnant may give birth to a baby with hearing impairment . Although only one in 1,000 patients with measles will develop encephalitis, 10 to 15 percent of those who do will die, and about another 25 percent will be left with permanent brain damage.

Prevention

Measles is a highly preventable infection. A very effective vaccine exists, made of live measles viruses that have been treated so that they cannot cause actual infection. The important markers on the viruses are intact, however, which causes an individual's immune system to react. Immune cells called antibodies are produced, which in the event of a future infection with measles virus quickly recognize the organism and kill it off. Measles vaccines are usually given to children at about 15 months of age; prior to that age, the baby's immune system is not mature enough to initiate a reaction strong enough to insure long-term protection from the virus. A repeat injection should be given at about ten or 11 years of age. Outbreaks on college campuses have occurred among students who were not immunized or who were incorrectly immunized.

Measles vaccine should not be given to pregnant women, however, in spite of the seriousness of gestational measles. The reason for not giving this particular vaccine during pregnancy is the risk of transmitting measles to the unborn child.

Parental concerns

New cases of measles began being reported in some countries—including Great Britain—in 2001 because of parents' fears about vaccine safety. The combined vaccine for measles, mumps , and rubella (MMR) was claimed to cause autism or bowel disorders in some children. However, the World Health Organization (WHO) position is there is no scientific merit to these claims. The United Nations expressed concern that unwarranted fear of the vaccine would begin spreading the disease in developing countries and ultimately in developed countries as well. Parents in Britain began demanding the measles vaccine as a separate dose, and scientists were exploring that option as an alternative to the combined MMR vaccine . Unfortunately, several children died during an outbreak of measles in Dublin because they had not received the vaccine. Child mortality due to measles is considered largely preventable, and making the MMR vaccine widely available in developing countries is part of WHO strategy to reduce child mortality by two-thirds by the year 2015.

Resources

BOOKS

Katz, Samuel L. "Measles (Rubeola)." In Principles and Practice of Pediatric Infectious Diseases , 2nd ed. Edited by Sarah S. Long et al. St. Louis, MO: Elsevier, 2003.

Maldonado, Yvonne. "Measles." In Nelson Textbook of Pediatrics. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2004.

PERIODICALS

Kerr, C. "Good response rate for MMRV vaccine." Lancet Infectious Disease 3 (December 2003): 748.

Stalkup, J. R. "A review of measles virus." Dermatology Clinics 20 (April 2002): 209–215.

ORGANIZATIONS

American Academy of Pediatrics (AAP). 141 Northwest Point Blvd., Elk Grove Village, IL 60007. Web site: http://www.aap.org.

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. Web site: http://www.cdc.gov.

Rosalyn Carson-DeWitt, MD Rebecca J. Frey, PhD