Measles is an infectious illness caused by a virus. Prior to the development of the measles vaccine, approximately 450,000 cases and 450 deaths due to measles were reported each year in the United States. Widespread measles vaccination has decreased these numbers by more than 99 percent. Measles is still a very common illness worldwide.
Measles is also known as rubeola.
The
cause of measles is an infection with the
measles virus. The measles virus is a single-stranded RNA virus, from the family
Paramyxovirus, of the genus
Morbillivirus. The measles virus only infects humans.
Measles is a highly contagious illness. It is spread by coughing and sneezing. If one person has measles, 90 percent of his or her susceptible close contacts will also become infected with the measles virus.
Incubation Period for Measles
When a person becomes infected with the measles virus, the virus begins to multiply within the cells that line the back of the throat and the lungs. After 8 to 12 days, on average, early
measles symptoms can begin. This period between the measles transmission and the start of measles symptoms is called the
measles incubation period.
Contagious Period for Measles
A person is not contagious during the
measles incubation period. A person is mildly contagious when he or she first experiences
measles symptoms. A person is most contagious about 4 days before the onset of the measles rash. Some risk of
measles transmission lasts until about 4 days after the rash starts.
Measles symptoms occur several days before the measles rash begins. These can include:
- High fever (up to 105°F or 40.6°C)
- Hacking cough
- Muscle and body aches
- Irritability
- Red, watery eyes (pinkeye)
- Runny nose
- Tiredness
- Swelling of the eyelids
- Small red lesions with blue-white centers (known as Koplik's spots) appearing on the inside of the mouth.
The early measles symptoms usually disappear 1-2 days after the rash appears, although the cough may continue until all measles symptoms are gone. The measles rash is a red, blotchy rash that usually appears about 14 days after exposure to the virus, and lasts 5 to 6 days
(see Pictures of Measles).
In order to make a measles diagnosis, the doctor will ask a number of questions (medical history) and perform a physical exam to look for signs or symptoms of measles.
Diagnosing measles can often be done just based on a person's symptoms and the findings of the physical exam. If the doctor is unsure, he or she may order a blood test to look for antibodies to the
measles virus, or a throat culture to look for the virus itself.
Several other medical conditions can have signs or symptoms that are similar to measles. The doctor will consider these conditions before diagnosing measles. Some of these conditions include:
- German measles (rubella)
- Syphilis (a sexually transmitted disease)
- Scarlet fever
- Mononucleosis (mono)
- Toxoplasmosis (infection in tissue)
- Reaction to medications
- Kawasaki syndrome (disease in the membrane of the upper respiratory tract).
There is currently no proven treatment that can kill the
measles virus; therefore, treatment for measles focuses on providing relief of
measles symptoms as the body fights the measles virus. This is called supportive care.
The majority of people with measles recover; however, 6 to 20 percent of the people who get the disease will develop a measles complication. Some measles complications can be very dangerous.
Measles causes
ear infections in nearly 1 out of every 10 children who get it. As many as 1 out of 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 leave your child deaf or mentally retarded.)
For every 1,000 children who get measles, 1 or 2 will die from it. Measles can also cause a pregnant woman to have a miscarriage, give birth prematurely, or have a low-birthweight baby.
Prior to 1963, almost everyone got measles; it was an expected life event. Each year in the United States, there were approximately 3 to 4 million cases, and an average of 450 deaths. Epidemic cycles occurred every 2 to 3 years. More than half the population had measles by the time they were 6 years old, and 90 percent had the disease by the time they were 15 years old.
However, after the measles vaccine became available, the number of measles cases dropped by 99 percent, and the epidemic cycles diminished drastically. Therefore, the best
prevention of measles is the measles vaccine.
References to measles can be found as far back as the 7th century A.D. In fact, the disease was described by Rhazes (Persian philosopher and physician) in the 10th century A.D. as "more dreaded than
smallpox." But all that changed in 1963, when the measles vaccine was first licensed in the United States.
Because of widespread vaccination, measles is rare in the United States. We still see measles among visitors to the United States and among U.S. travelers returning from other countries. When the virus is brought into the United States, it sometimes causes outbreaks; however, because most people in the United States have been vaccinated, these outbreaks are usually small. Today, about one quarter of measles cases occur in adults, and nearly half occur in unvaccinated children, mostly minorities.
Measles is still a very common illness worldwide.
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