Mumps is caused by the mumps virus, a single-stranded RNA virus

The mumps virus is the pathogen that causes mumps infection. It belongs to a family of viruses called paramyxoviruses, which also includes measles and respiratory syncytial virus (RSV). The virus spreads from person to person through respiratory droplets — the tiny particles released when an infected person coughs, sneezes, or talks.

Once the mumps virus enters your body through your nose or mouth, it travels to your lymph nodes and salivary glands, where it multiplies. This is why mumps typically causes swelling and tenderness in the glands below your jaw and ears. The virus can also spread to other parts of your body, including the brain, pancreas, and reproductive organs.

Key Takeaways

  • The mumps virus is a paramyxovirus that spreads through respiratory droplets when infected people cough or sneeze.
  • The virus multiplies in your salivary glands and lymph nodes, causing the characteristic swelling below the jaw and ears.
  • A person with mumps is most contagious from two days before symptoms appear through five days after the swelling starts.
  • The MMR vaccine prevents mumps infection by training your immune system to recognize and fight the virus before it takes hold.

How the mumps virus spreads between people

The mumps virus travels through the air in respiratory droplets. When someone with mumps coughs or sneezes, they release tiny particles containing the virus into the air. If you breathe in these particles, the virus can infect your respiratory tract and begin to multiply.

You can also catch mumps by touching a contaminated surface and then touching your face, though this is less common than airborne transmission. The virus survives only briefly on surfaces, so direct contact with respiratory droplets is the main route of infection.

A person with mumps is most contagious from two days before their symptoms appear through five days after the swelling in their salivary glands begins. This means people can spread the virus without knowing they have it, since they may feel sick before the telltale swelling appears.

What happens when the mumps virus enters your body

When you inhale the mumps virus, it first infects the cells lining your respiratory tract. From there, it enters your bloodstream and travels to your salivary glands — the glands that produce saliva in your mouth. The virus multiplies rapidly in these glands, causing inflammation and the painful swelling you feel below your jaw and in front of your ears.

Your immune system recognizes the virus as a threat and mounts a response, which causes fever and body aches. In some cases, the virus spreads beyond the salivary glands to other organs. This can lead to complications such as meningitis (infection of the membranes around the brain and spinal cord), encephalitis (brain inflammation), or pancreatitis (pancreas inflammation).

Why the MMR vaccine stops the mumps virus

The MMR vaccine contains a weakened form of the mumps virus. When you receive the vaccine, your immune system learns to recognize the virus without causing a full infection. Your body produces antibodies — proteins that fight infection — that remember the mumps virus for years or decades.

If you are later exposed to the real mumps virus, your immune system can identify it immediately and destroy it before it multiplies enough to make you sick. This is why vaccinated people rarely develop mumps, and when they do, their symptoms are usually much milder than in unvaccinated people.

The MMR vaccine is given in two doses, typically at 12 to 15 months of age and again at 4 to 6 years old. Most people who receive both doses develop strong immunity to mumps.

The difference between mumps virus and other similar viruses

The mumps virus belongs to the paramyxovirus family, which includes several other viruses that cause respiratory illness. Measles virus, another paramyxovirus, also causes fever and a rash but spreads more easily and causes more severe complications. Respiratory syncytial virus (RSV) causes cold-like symptoms but does not typically cause salivary gland swelling.

The mumps virus is distinct because it has a strong affinity for salivary glands, meaning it preferentially infects and multiplies in those tissues. This is why salivary gland swelling is the hallmark sign of mumps and helps doctors tell it apart from other viral infections.

What happens after the mumps virus clears from your body

Once your immune system defeats the mumps virus, the infection ends. The virus does not remain dormant in your body the way some viruses do — it is eliminated completely. After recovery, your immune system retains a memory of the mumps virus, which provides lifelong immunity in most people.

This is why mumps was once a common childhood illness but is now rare in countries with high MMR vaccination rates. People who have had mumps naturally, or who have been vaccinated, are protected against future infection.

Frequently Asked Questions

Can you catch mumps more than once?

No. Once you have had mumps or been vaccinated against it, your immune system remembers the virus and protects you from future infection. Reinfection is extremely rare.

Is the mumps virus the same as the measles virus?

No. While both are paramyxoviruses and both are prevented by the MMR vaccine, they are different viruses that cause different symptoms. Measles causes a rash that spreads across the body, while mumps causes swelling in the salivary glands.

How long does the mumps virus stay in your body?

The active infection typically lasts one to two weeks. After that, your immune system has cleared the virus completely. You are no longer contagious after five days of swelling, even though you may still feel unwell.

Can adults catch the mumps virus?

Yes. Adults who were not vaccinated or who did not have mumps as a child can catch it. Mumps in adults tends to cause more severe symptoms and higher rates of complications than in children.

Does the mumps virus cause permanent damage?

Most people recover from mumps without lasting effects. However, mumps can cause permanent hearing loss in one or both ears, and in rare cases can lead to infertility in males if the virus infects the testicles. Vaccination prevents these complications.