More than 400 people have been infected with mumps in Arkansas.

The enormous outbreak, reported on Friday, has sparked an urgent investigation to contain the spread.

Cities and towns across the state have recorded at least 427 recent cases.

Most of the patients are children, with more than 30 schools reporting numerous infections.

Mumps is a virus of the salivary gland. The infection is incurable and can lead to devastating illnesses in adults. Medics fear a new strain of the virus could be developing in Arkansas

WHAT IS MUMPS? Mumps is a virus of the salivary gland. It is spread through saliva, commonly on glasses, plates and cutlery. The infection is incurable and can lead to devastating health concerns in adults. Sufferers have lost their hearing, become infertile, and had swollen brains. SYMPTOMS? Some people do not experience any symptoms. Typically, symptoms include puffy cheeks, swollen glands, headaches, a fever, chills, fatigue, muscle aches, and a lack of appetite. Sufferers have described feeling pain in their stomach, neck, pelvis, and testicles. Advertisement

Any students yet to get the MMR (mumps, measles, rubella) vaccination have been ordered to stay at home for 26 days if they are near an outbreak zone.

Mumps is a virus of the salivary gland.

The infection is incurable and can lead to devastating health concerns in adults.

Sufferers have lost their hearing, become infertile, and had swollen brains.

Some people do not experience any symptoms.

Typically, symptoms include swollen glands, headaches, a fever, chills, fatigue, and a lack of appetite.

Sufferers have described feeling pain in their stomach, neck, pelvis, and testicles.

Since widespread implementation of the MMR jab, it is now barely reported.

As these maps (below) show, incidents of mumps are few and vaccinations rates are high.

A mumps infection can also travel to and infect other parts of the body.

When this occurs it often causes swelling and discomfort in the affected area.

One of those developments is orchitis, a swelling infections in the testicles which affects around 25% of post-pubescent males.

Roughly half the time it also causes the affected testicle to shrink in size.

Mumps can also lead to viral meningitis, acute pancreatitis, and oophoritis (swelling of one or both ovaries).

In very rare cases (around 0.1 per cent) mumps can cause encephalitis, a life-threatening inflammation of the brain.

Symptoms of encephalitis include flu-like symptoms, headache, confusion, dizziness, change in personality, change in behavior, drowsiness, disorientation, seizures, and loss of consciousness.

Anyone suffering these symptoms after contracting mumps should call 911 immediately. This condition requires emergency treatment in a hospital’s intensive care unit (ICU).