Mumps is a viral infection of the salivary glands, especially the parotid glands that run along the angle of the jaw in front of and below each ear. Children between the ages of 5 and 10 are most likely to contract mumps. Being infected once gives you lifelong immunity.
Mumps is most common around the month of March. It usually appears in scattered individual cases, though there are occasional local epidemics among unvaccinated children. It's less infectious than chickenpox or measles. Unvaccinated adults who never had the disease are at much higher risk of complications than are children, but mumps rarely causes serious problems.
A vaccine for mumps dramatically reduced the incidence of the disease since its introduction in 1967. In the 1950s, Canada had about 30,000 cases a year. The advent of the vaccine cut that number in half. Today, the annual incidence is under 300 cases per year.
Mumps is caused by an organism called a paramyxovirus. It's transmitted via the mouth by tiny drops of saliva from talking, sneezing, sharing drinks, kissing, or coughing. The virus can land on an object that others then handle. Once it's on your hand, there's a good chance it will find its way into your mouth, especially if you're a young child.
Mumps is contagious for about a week before the glands swell, and about 9 days afterwards, so people can transmit it before they know they have it. This is common for most viral diseases.
Up to one-third of people infected feel no symptoms. Others have a low-grade fever, headache, weakness, fatigue, and loss of appetite starting 14 to 24 days after they are actually infected. About a day after the onset of fever, the parotid gland near the ear begins to swell and ache - this makes chewing and swallowing painful. The body's temperature rises to 39.5°C to 40°C (103°F to 104°F).
The swelling and tenderness worsens over the next 3 days and may extend forward of the jaw and, for some, down the neck, depending on whether other salivary glands are involved. In the majority of mumps cases, both the right and left parotid glands are swollen. The fever typically lasts only 1 to 3 days but can persist for a week. The swelling of the glands tends to resolve after about one week.
That's usually as far as it goes, even in adults. 1 in 5 adolescent or adult males, however, suffers orchitis, an infection and inflammation of the testicles. This can be very painful, but it almost never results in sterility. Women can get an infection in the ovaries, but it's mild and harmless.
1 in 30 people infected get pancreatitis (inflammation of the pancreas) with vomiting and stomachache that quickly clears up. A similar number develop hearing problems due to otitis media, which is also a temporary side effect of mumps.
Any viral disease carries some risk of severe complications like encephalitis (brain inflammation) or meningitis (inflammation of the membranes around the brain and spinal cord) during or after the initial infection. The risk of developing encephalitis with mumps is about 1 in 5,000, and for meningitis the risk is 1% to 10%. There is a very small risk of miscarriage in women who get infected while pregnant.