Mumps is caused by the mumps virus.
When you get mumps, the virus moves from your respiratory tract (nose, mouth and throat) into your parotid glands. It is here that it begins to reproduce and this causes the glands to swell.
It can spread to other parts of your body such as your brain and pancreas. It can also spread to testicles in boys and men and ovaries in girls and women.
How mumps is spread
An infected person can spread the virus by coughing or sneezing. This releases tiny droplets of contaminated saliva. These droplets can be breathed in by another person.
An infected person may also spread mumps by touching their nose or mouth. They may then transfer the virus onto an object. If someone else touches the object shortly afterwards, they can transfer the virus into their respiratory tract.
People with mumps are usually most infectious from a few days before their parotid glands swell until a few days afterwards. You should avoid work or school for 5 days after your symptoms first develop if you're diagnosed with mumps.
Mumps can also be passed on by people who are infected with the virus but do not have any obvious symptoms.