Measles explained

Measles is a highly infectious illness caused by the rubeola virus.

Also known as rubeola or morbilli, measles is an endemic disease, meaning it is continually present in a community, and many people develop resistance.

However, if measles enters an area where the people have never been exposed, the result can be devastating.

Vaccination prevents many cases of measles around the world. The World Health Organization estimate that 2.6 million people who have not had the vaccine die of measles every year.


Measles is caused by infection with the rubeola virus. The virus lives in the mucus of the nose and throat of an infected child or adult.

The disease is contagious for 4 days before the rash appears, and it continues to be contagious for about 4 to 5 days after.

Infection spreads through:

  • physical contact with an infected person
  • being near infected people if they cough or sneeze
  • touching a surface that has infected droplets of mucus and then putting fingers into the mouth, or rubbing the nose or eyes

The virus remains active on an object for 2 hours.

How does a measles infection develop?

As soon as the virus enters the body, it multiplies in the back of the throat, lungs, and the lymphatic system. It later infects and replicates in the urinary tract, eyes, blood vessels, and central nervous system.

The virus takes 1 to 3 weeks to establish itself, but symptoms appear between 9 and 11 days after initial infection.

Anyone who has never been infected or vaccinated is likely to become ill if they breathe in infected droplets or are in close physical contact with an infected person.

Approximately 90 percent of people who are not immune will develop measles if they share a house with an infected person.

Diagnosis and treatment

A doctor can normally diagnose measles by looking at the signs and symptoms. A blood test will confirm the presence of the rubeola virus.

In most countries, measles is a notifiable disease. The doctor has to notify the authorities of any suspected cases. If the patient is a child, the doctor will also notify the school.


Complications from measles are fairly common. Some can be serious.

People most at risk are patients with a weak immune system, such as those with HIV, AIDS, leukemia, or a vitamin deficiency, very young children, and adults over the age of 20 years.

Older people are more likely to have complications than healthy children over the age of 5 years.

Measles vaccination

In the United States, the measles, mumps, and rubella (MMR) vaccine is routinely given at 12 to 15 months of age, followed by a booster shot before entering school at the age of 4 to 6 years.

Newborns carry their mother’s immunity for a few months after birth if their mothers are immune, but sometimes the vaccine is recommended before the age of 12 months, and as early as 6 months.

This may happen if they are, or are likely to be, in an area where there is a serious outbreak.

The WHO estimate that measles vaccination programs led to a 79 percent drop in measles deaths globally, from 2000 to 2015, preventing around 20.3 million deaths.


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