Rheumatic fever is a serious complication that can develop following an untreated throat infection (by a type of bacteria called group A streptococcus).
Symptoms usually last around four weeks, but can sometimes persist for several months.
Rheumatic fever is rare in the UK.
The symptoms of rheumatic fever aren't caused by the bacteria itself, but the immune system's response to it.
When your body senses the streptococcal infection, it sends antibodies (infection-fighting molecules) to fight it. However, the antibodies sometimes attack the tissues of parts of the body, such as the joints or heart instead. If the antibodies attack your heart, they can cause your heart valves to swell, which can lead to scarring of the valve "doors" (called leaflets or cusps).
Read more about the causes of rheumatic fever.
There's currently no cure for rheumatic fever. Treatment involves relieving the symptoms with medication and trying to prevent permanent damage to the body, particularly the heart.
Once a person has had an attack of rheumatic fever, it's very common for them to have future attacks. This can be prevented by taking a long-term course of antibiotics.
Read more about treating rheumatic fever.
Rheumatic fever can cause permanent damage to the valves of the heart, which is known as rheumatic heart disease.
Read more about the complications of rheumatic fever.
Rheumatic fever is very common in poorer parts of the world, such as Africa, the Middle East and South America, where there's over-crowding, poor sanitation and limited access to medical treatment. It's estimated that just under half a million new cases of rheumatic fever occur worldwide each year.
The condition is now very rare in the UK as a result of higher standards of living and medical care. It's estimated that less than 1 in 100,000 people in the UK develop rheumatic fever.
Most cases of rheumatic fever first develop in children between the ages of five and 15. It's less likely to affect younger adults, and it's very rare for it to develop in adults who are 35 years of age or over. Both sexes are equally affected.
The outlook for people with rheumatic fever depends on whether they've sustained significant heart damage.
If the heart is damaged, it's unlikely to fully recover. In such cases, the symptoms of rheumatic heart disease, such as shortness of breath and constant tiredness, will continue.
If the heart is undamaged, long-term use of antibiotics should prevent rheumatic fever occurring again, which should hopefully prevent the heart becoming damaged.
Deaths associated with rheumatic heart disease are very rare in the UK and the rest of the developed world.