Measles is a respiratory disease caused by a virus. The disease and the virus that causes it share the same name. The disease is also called rubeola. This virus normally grows in the cells that line the back of the throat and lungs.
The virus is an enveloped virus (100–200 nm in diameter), with a core of single-stranded RNA. Two membrane envelope proteins are important in pathogenesis. They are the F (fusion) protein, which is responsible for fusion of virus and host cell membranes, viral penetration, and hemolysis, and the H (hemagglutinin) protein, which is responsible for adsorption of virus to cells. There is only one antigenic type of measles virus. The virus is rapidly inactivated by heat, light, acidic pH, ether, and trypsin. It has a short survival time (less than 2 hours) in the air or on objects and surfaces.
It 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 US 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 20 million cases and 164,000 deaths each year. More than half of the deaths occur in India.
People who do not have immunity to it (not vaccinated or who never had it before) are at an increased risk of being infected when exposed to a person with it.
The symptoms of measles generally begin about 7-14 days after a person is infected, and include: blotchy rash, fever, cough, runny nose, red, watery eyes (conjunctivitis), feeling run down, achy (malaise), tiny white spots with bluish-white centers found inside the mouth (Koplik’s spots). A typical case begins with mild to moderate fever, cough, runny nose, red eyes, and sore throat. Two or three days after symptoms begin, Koplik’s spots may appear inside the mouth. Three to five days after the start of symptoms, a red or reddish-brown rash appears. The rash usually begins on a person’s face at the hairline and spreads downward to the neck, trunk, arms, legs, and feet. When the rash appears, a person’s fever may spike to more than 104 degrees Fahrenheit. After a few days, the fever subsides and the rash fades.
About one out of 10 children with it also gets an ear infection, and up to one out of 20 gets pneumonia. About one out of 1,000 gets encephalitis, and one or two out of 1,000 die. While it is almost gone from the United States, it still kills nearly 200,000 people each year around the world. It can also make a pregnant woman have a miscarriage or give birth prematurely.
The virus is highly contagious and can be spread to others from four days before to four days after the rash appears. It 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.
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. Measles is a disease of humans; the virus is not spread by any other animal species.
Measles can be prevented by the combination MMR (measles, mumps, and rubella) vaccine. In the decade before the vaccination program began, an estimated 3–4 million people in the United States were infected each year, of whom 400–500 died, 48,000 were hospitalized, and another 1,000 developed chronic disability from measles encephalitis. Widespread use of the vaccine has led to a greater than 99% reduction in cases in the United States compared with the pre-vaccine era, and in 2009, only 71 cases were reported in the United States. However, it is still common in other countries. The virus is highly contagious and can spread rapidly in areas where vaccination is not widespread. It is estimated that in 2008 there were 164,000 virus related deaths worldwide—that equals about 450 deaths every day or about 18 deaths every hour.
Each year, on average, 60 people in the United States are reported to have measles. But, in 2011, the number of reported cases was higher than usual—222 people had the disease. Nearly 40% of these people got measles in other countries, including countries in Europe and Asia. They brought the disease to the United States and spread it to others. This caused 17 measles outbreaks in various U.S. communities.
The virus was declared eliminated from the United States in 2000. So, the disease no longer spreads year round in this country. But, the disease is still common throughout the world, including some countries in Europe, Asia, the Pacific, and Africa. Anyone who is not protected against measles is at risk of getting infected when they travel internationally. They can bring it to the United States and infect others. Unvaccinated people put themselves and others at risk for measles and its serious complications.
The virus can live on infected surfaces, in the air, or on objects 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.
Environmental surfaces should be properly cleaned using a disinfectant that is effective against enveloped viruses.