Measles is highly contagious and can be spread to others from four days before to four days after the rash appears. Measles is so contagious that if one person has it, 90% of the people close to that person who are not immune will also become infected with the measles virus.

The virus lives in the mucus in the nose and throat of the infected person. When that person sneezes or coughs, droplets spray into the air. The droplets can get into other people's noses or throats when they breathe or put their fingers in their mouth or nose after touching an infected surface. The virus can live on infected surfaces for up to 2 hours and spreads so easily that people who are not immune will probably get it when they come close to someone who is infected.

Measles is a disease of humans; measles virus is not spread by any other animal species.

While measles is almost gone from the United States, it still kills nearly 200,000 people each year around the world.

About 30% of measles cases develop one or more complications, including:

• Pneumonia, which is the complication that is most often the cause of death in young children.
• Ear infections occur in about 1 in 10 measles cases and permanent loss of hearing can result.
• Diarrhea is reported in about 8% of cases.

These complications are more common among children under 5 years of age and adults over 20 years old.

Even in previously healthy children, measles can be a serious illness requiring hospitalization. As many as 1 out of every 20 children with measles gets pneumonia, and about 1 child in every 1,000 who get measles will develop encephalitis. (This is an inflammation of the brain that can lead to convulsions, and can leave the child deaf or mentally retarded.) For every 1,000 children who get measles, 1 or 2 will die from it. Measles also can make a pregnant woman have a miscarriage, give birth prematurely, or have a low-birth-weight baby.

Other rash-causing diseases often confused with measles include roseola (roseola infantum) and rubella (German measles).

SSPE (Subacute Sclerosing Panencephalitis)

SSPE is a very rare, but fatal degenerative disease of the central nervous system that results from a measles virus infection acquired earlier in life. Analysis of data from an outbreak of measles in the United States during 1989-1991 suggests a rate of 4-11 cases of SSPE per 100,000 cases of measles. A risk factor for developing this disease is measles infection at an early age. Studies in the United Kingdom indicate that 18 out of every 100,000 people who get measles when they are less than a year old will develop SSPE. This is compared to 1.1 per 100,000 in those infected after 5 years of age. On average, the symptoms of SSPE begin 7 to 10 years after measles infection, but they can appear anytime from 1 month to 27 years after infection.

 Signs of SSPE

The first signs of SSPE may be changes in personality, a gradual onset of mental deterioration and myoclonia (muscle spasms or jerks). The diagnosis of SSPE is based on signs and symptoms and on test results, such as typical changes observed in electroencephalographs, an elevated anti-measles antibody (IgG) in the serum and cerebrospinal fluid, and typical histologic findings in brain biopsy tissue.

SSPE progresses in stages, which can vary from person to person. In some cases, the cognitive decline may continue for years before progression to more severe neuromuscular disorders are observed, and thus the diagnosis may be delayed or missed. There are reports of remission and some treatments are available; however, the average survival is one to two years.

Genetic Analysis

All of the genetic analyses of viral material derived from brain tissue of SSPE patients have revealed sequences of wild-type measles virus, never vaccine virus. There is no evidence that measles vaccine can cause SSPE. Cases of SSPE in patients who have a history of measles vaccination but no knowledge of having had measles either had an undiagnosed rash illness or possibly a mild measles infection early in life due to the presence of maternal antibody. Therefore, physicians should consider SSPE in the differential diagnosis of encephalitis even when the patient does not have a history of measles.

Measles Incidence

Measles is very rare in countries and regions of the world that are able to keep vaccination coverage high. In North and South America, Finland, and some other areas, endemic measles transmission is considered to have been interrupted through vaccination. There are still sporadic cases of measles in the United States because visitors from other countries or U.S. citizens traveling abroad can become infected before or during travel and spread the infection to unvaccinated or unprotected persons.

Worldwide, there are estimated to be 10 million cases and 197,000 deaths each year. More than half of the deaths occur in India. For more information on measles in the United States and worldwide, visit the Global Elimination page.

Measles History

One of the earliest written descriptions of measles as a disease was provided by an Arab physician in the 9th century who described differences between measles and smallpox in his medical notes.

A Scottish physician, Francis Home, demonstrated in 1757 that measles was caused by an infectious agent present in the blood of patients. In 1954 the virus that causes measles was isolated in Boston, Massachusetts, by John F. Enders and Thomas C. Peebles. Before measles vaccine, nearly all children got measles by the time they were 15 years of age. Each year in the United States about 450 people died because of measles, 48,000 were hospitalized, 7,000 had seizures, and about 1,000 suffered permanent brain damage or deafness. Today there are only about 50 cases a year reported in the United States, and most of these originate outside the country.