The measles is an upper respiratory viral infection that can be a relatively mild disease for many people, but about 20 percent of those infected with the virus can experience complications that require hospitalization, according to Amesh Adalja, MD, assistant professor and senior scholar who specializes in emerging infectious disease at the Johns Hopkins Center for Health Security in Baltimore. "It was a very common disease in the United States until a highly effective vaccine was introduced in the early 1960s," he says.

Causes and Risk Factors of Measles

Measles is caused by a virus in the paramyxovirus family and is typically transmitted through direct contact and air, according to the World Health Organization (WHO).
When measles virus enters the body, it initially infects immune cells known as macrophages and dendritic cells. The infected cells replicate and move to the lymph nodes, where they transfer the virus to lymphocytes (types of white blood cells) known as B and T cells, per an August 2016 review in Viruses.

Those infected cells move throughout the body and release virus particles into the blood. The spleen, lymph nodes, liver, thymus, skin, and lungs can all become infected with the virus.

The infection of the lungs causes the coughing and sneezing, which is the main way that measles is spread. The virus 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.
Only humans (not animals) transmit the 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 the WHO.

Duration of Measles

The first indication of the disease is usually a high fever, which typically starts about 10 to 12 days after exposure to the virus.The fever usually lasts four to seven days; other symptoms, such as a runny nose, cough, red and watery eyes, and small white spots inside the cheeks, can develop during this stage.

After this period, a rash (usually on the face and upper neck) appears. Over about a three-day period it spreads all over the body, eventually reaching the hands and feet. The rash typically lasts five to six days until it fades.

Complications of Measles

About 1 out of 5 unvaccinated people in the United States who gets measles is hospitalized, according to the CDC.Complications can happen to anyone, but certain groups are at a higher risk including:
  • Children younger than 5
  • Adults older than 20
  • Pregnant women
  • People who have compromised immune systems, for example those with leukemia or HIV infection
Pneumonia According to the CDC, about 1 out of every 20 children with measles gets pneumonia, which is infection of the lungs. It’s the most common cause of death from measles in children.
More on Complications

Is It a Cold, the Flu, or Pneumonia?

Brain Infection Also called encephalitis, this infection results in swelling of the brain. This happens in about 1 out every 1,000 children who get the measles, and it can lead to hearing loss or permanent intellectual disability, according to the CDC.

Ear Infection Approximately 10 percent of children who get the measles also get an ear infection, which can result in permanent hearing loss, according to the CDC.

Subacute Sclerosing Panencephalitis (SSPE) This fatal disease of the central nervous system is a very rare complication that results from a measles infection. It generally happens 7 to 10 years after a person has the measles infection. This disease is rarely reported in the United States.

COVID-19 and Measles

One of the tragedies of the COVID-19 pandemic, says Adalja, is that measles vaccination efforts around the world are faltering. "Even in the United States, we saw measles vaccination rates go down during the height of the pandemic, in the spring when there were stay-at-home orders and nonemergency care was suspended," he says. Measles remains a threat, and the more people that get the measles vaccine, the quicker we can eradicate this virus from the planet, he adds.

Resources We Love

Centers for Disease Control and Prevention (CDC)

The CDC website provides comprehensive, up-to-date information about infectious diseases, such as measles, found in the United States and around the world.

This website, from the American Academy of Family Physicians, offers education and medical advice on a variety of conditions, including measles.


MedlinePlus is a service of the National Library of Medicine, the world’s largest medical library, which is part of the National Institute of Health (NIH). The agency provides health and wellness information in both English and Spanish.

Additional reporting by Joseph Bennington-Castro.

Editorial Sources and Fact-Checking

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