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Measles is a viral respiratory illness characterized by high fever and generalized rash. Symptoms start ten to twelve days after airborne exposure and include fever, malaise, conjunctivitis, runny nose, and cough. About fourteen days after exposure, a maculopapular rash appears at the hairline, extends to the face and upper neck, and, over the next three days, spreads down the body to the hands and feet. Although measles is usually not severe in developed countries, it can lead to serious complications including diarrhea (8% of cases), ear infections (7%), pneumonia (6%), encephalitis (0.1%), subacute sclerosing panencephalitis (SSPE)(0.001%), and death (0.2%). Measles is much more serious in developing countries, causing about one million deaths annually during the 1990s. The case fatality rate can be as high as 25 percent, with deaths often caused by secondary infections such as diarrhea or pneumonia. Measles is also a common cause of blindness in the developing world.

Measles is one of the most contagious diseases in the world. The virus, a paramyxovirus containing a single strand of RNA, is normally spread through respiratory droplets and can be transmitted from four days before to four days after rash onset. Before vaccines were introduced, nearly everyone was infected by age ten to twelve years. Immunity is lifelong following infection.

A live attenuated vaccine was licensed in 1963, and further attenuated vaccines are now used around the world. The vaccine is about 95 percent effective in the United States when administered at the recommended age of twelve to fifteen months, and immunity is considered lifelong. It is usually given in conjunction with the mumps and rubella vaccines. Children in developing countries are vaccinated at nine months of age because of the higher risk of infection in infancy.

Routine treatment of measles includes supportive care such as oral rehydration therapy for diarrhea and respiratory care for patients with pneumonia. Antibiotics are used to treat secondary bacterial infections. Although antiviral medications have been used to treat complex measles infections, there are few studies to confirm their effectiveness. High-dose vitamin A therapy reduces mortality and prevents blindness and is recommended by the World Health Organization for children in developing countries.

Global measles eradication has been a goal since the development of an effective vaccine. Humans are the only reservoir for the measles virus, which can survive only hours in the environment. Endemic measles can be eliminated from large geographic areas using intensive vaccination programs, as seen in the United States in the late 1990s. However, measles is so infectious that immunization rates of at least 90 to 95 percent must be attained to interrupt transmission. In addition, the billions of doses required to achieve eradication highlight the need for injection safety and the potential development of needle-free vaccination methods. Finally, the HIV (human immunodeficiency virus) epidemic presents several barriers to measles eradication. HIV-infected persons have a lower response to measles vaccination, develop more severe cases of the disease, and, theoretically, may be infectious for longer periods of time. There is hope that these challenges will be surmounted and measles will be eradicated, following smallpox into the history books.

SONIA KLEMPERER-JOHNSON

MARK PAPANIA

(SEE ALSO: Communicable Disease Control; Disease Prevention; Eradication of Disease; Immunizations)