Measles: Causes, symptoms
What Is Measles?
Measles is a highly contagious and potentially serious respiratory illness caused by a virus.
The virus causes a number of , most notably:
- High fever
- Runny nose
- Red, watery eyes
- White spots in the mouth
It can also lead to life-threatening complications, including pneumonia, diarrhea, and encephalitis (brain inflammation).
Measles is also known as rubeola, which is not the same thing as rubella (sometimes called German measles or three-day measles).
Rubella is a different virus-borne illness that causes similar symptoms, including a red rash.
Measles was once common in the United States — in the decade before 1963, an estimated 3 to 4 million people were infected with measles and 400 to 500 people died from the disease each year, according to the Centers for Disease Control and Prevention (CDC).
Developed in 1963, the measles vaccine greatly reduced infection rates. The vaccine is combined with mumps and rubella vaccines to form a combination vaccine called MMR.
The measles vaccine can also be combined with the mumps, rubella, and varicella (chickenpox) vaccines to form MMRV.
Measles was declared "eliminated" from the United States in 2000, meaning that there was an absence of continuous disease transmission for a whole year and the disease is no longer native to the country.
However, that's not to say people don't ever get measles: Outbreaks of measles can still happen.
From 2000 to 2013, between 37 and 220 cases of measles were reported in the United States. Most of those cases originated outside the country, according to the CDC.
In 2015, more than 150 people in the United States reportedly got the disease, mostly from a measles outbreak at the Disneyland amusement park in Anaheim, California.
Worldwide, measles is still one of the leading causes of childhood death, according to the World Health Organization (WHO).
In 2013, 145,700 people died from the illness — and most of them were children under 5 years old.
This rate is down from the estimated 544,200 people who died from measles in 2000 and the 2.6 million people who died each year before 1980, when vaccination became more widespread.
Cause of Measles
Measles is caused by the measles virus, which is a member of the genus Morbillivirus in the virus family Paramyxoviridae.
The Morbillivirus genus also includes various other viruses, including canine distemper virus, which causes distemper in dogs and some other animals.
When measles virus enters the body, it initially infects macrophages (a type of white blood cell) in the air sacs in the lungs and dendritic cells (another type of immune system cell) in the bronchial airways, according to 2012 report in the journal Current Opinion in Virology.
From there, the virus infects and rapidly replicates in local bronchial tissue associated with the lymphatic system — part of the circulatory and immune systems that's responsible for making and transporting lymph, a clear fluid containing infection-fighting white blood cells — and the lymph nodes that surround the bronchi and trachea.
Measles virus spreads to other organs and parts of the body through infected lymphocytes (a subtype of white blood cells, which includes T cells and B cells) that travel through the lymphatic system.
Specifically, the virus infects epithelial cells, a type of tightly packed, protective cell that lines or covers the inner cavities and outside surface of the body — this includes the mucus-secreting cells of the nose and throat, which helps the virus spread to other people (through coughing and sneezing).
Spread of Measles
Humans, not other animals, transmit measles virus. You are at risk of getting measles if you are not vaccinated, were vaccinated but didn't develop immunity to the virus, or travel in undeveloped countries with low rates of measles vaccinations, according to WHO.
Measles is most often spread through coughing and sneezing, and can survive on a surface or in an airspace where an infected person coughed or sneezed for up to two hours, according to the CDC.
You can get measles if you breathe in contaminated air or touch your eyes, nose, or mouth after touching an infected surface. You can pass on the virus to someone else four days before and after a rash appears.
Measles is highly contagious — so much so that 90 percent of people who are close to an infected person and not immune to the virus will catch it, according to the CDC.
Video: Difference Between Measles and Rubella
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