What is rheumatic fever and how does it lead to heart damage?

Most people think rheumatic fever is something that only happens to children in low-income countries. I see patients every month in Bangkok who had it as a child, stopped their penicillin years ago, and have no idea what state their heart valves are in. I also see adults who have never been diagnosed but whose symptoms, once you ask the right questions, point straight to it. This article covers what you actually need to know: the warning signs, who is at risk, how it is diagnosed, and what treatment looks like in Bangkok.

Recognising the early warning signs: when a sore throat becomes serious

Most sore throats are viral and clear on their own. Strep throat, caused by group A streptococcus, is the exception that needs antibiotics. The two can be hard to tell apart. Strep throat usually causes a severe sore throat, fever, swollen neck glands, and white patches on the tonsils, without a cough. If that sounds like you, get tested rather than waiting it out.

What I tell patients is this: rheumatic fever does not develop during the sore throat itself. It develops two to four weeks later, once the immune response has been set in motion. By then, the throat is often completely fine. Patients rarely connect the two events. That is exactly where things go wrong.

For expats in Bangkok, the gap is practical. You self-treat a bad sore throat with paracetamol, it clears up, and six weeks later your joints are swollen and you have a fever. A strep infection that gets better on its own can still trigger rheumatic fever in susceptible people. A severe sore throat with fever is worth a same-day clinic visit, not self-management from the pharmacy.

Who is at risk? Age, geography, and rheumatic fever in Southeast Asia

Rheumatic fever is most common in children and teenagers between five and fifteen. Adults can develop it, but first attacks in adulthood are less common.

Where you grew up matters. Rheumatic fever is far more common across Southeast Asia, South Asia, sub-Saharan Africa, and parts of the Pacific than in Western Europe or North America. Thailand’s burden has decreased with better healthcare access, but it is not negligible. The Thai Ministry of Public Health has documented rheumatic heart disease as a meaningful cause of cardiac problems, particularly in areas with less consistent access to antibiotics. If you grew up in a region where strep throat was commonly left untreated, that background risk is clinically relevant now.

Not everyone with untreated strep throat develops rheumatic fever. There is a genetic element we do not fully understand. What is clear is that treating strep throat promptly with antibiotics is the most reliable way to prevent the first episode.

Acute rheumatic fever criteria: the Jones criteria explained

Rheumatic fever is not diagnosed with a single test. Doctors use a structured framework called the Jones criteria, last updated in 2015, which divides findings into major and minor categories. A diagnosis typically needs two major findings, or one major and two minor, plus evidence of a recent strep infection.

The major findings are the ones that matter most. Carditis, meaning heart inflammation, is the most serious. It can affect the outer lining, the muscle, or the valves. The 2015 update was significant because it added valve abnormalities detected on echocardiogram, even without an audible murmur. That matters because silent valve damage can still progress.

Arthritis is the most common major finding. In most patients, it moves between large joints in sequence rather than hitting several at once. In Southeast Asian populations, including Thailand, the criteria allow for a single joint or widespread joint pain to count, because presentations here can look different.

Sydenham chorea is an involuntary movement disorder caused by brain inflammation. It can appear months after the strep infection, sometimes as the only sign of rheumatic fever at that point. A skin rash with a spreading, ring-like border and small lumps over bony prominences are also major findings but appear less often.

Minor findings include fever, elevated inflammatory markers on blood tests, a high white cell count, and a prolonged PR interval on the ECG. These support the diagnosis but are not specific enough on their own.

Evidence of a recent strep infection is required, not optional. A throat swab, rapid strep test, or a blood test called the antistreptolysin O titre, or ASOT, can provide this. The ASOT stays elevated for weeks to months after infection, which makes it the most practically useful test when symptoms appear long after the throat has cleared.

Rheumatic fever in adults: a condition that does not only affect children

The assumption that rheumatic fever only affects children creates a real diagnostic blind spot. Adults with fever, migratory joint pain, and a recent sore throat sometimes wait weeks for a diagnosis because rheumatic fever is not the first thing anyone considers.

Adult presentations often lead with joint symptoms. The arthritis can be severe enough to be temporarily disabling, which tends to dominate the picture. Cardiac involvement, if present, may only show up on echocardiogram. Chorea is less common in adults but does occur.

Adults who had rheumatic fever as children are at much higher risk from any subsequent episode. Each recurrence can add more valve damage. If you stopped your penicillin years ago, perhaps after moving countries or losing contact with your original doctor, your prophylaxis status needs to be reviewed. An echocardiogram to check your current valve anatomy is the other immediate priority.

Diagnosing rheumatic fever in Bangkok: what to expect at your appointment

The first step is a detailed history. I ask about any recent sore throat, how severe it was, whether antibiotics were taken, and exactly when the joint or other symptoms started. Chest pain, palpitations, breathlessness, unusual movements, and any personal or family history of rheumatic fever or heart disease are all relevant.

Blood tests at the first visit include a full blood count, ESR, CRP, and ASOT. A throat swab is worth taking if there are any ongoing throat symptoms. An ECG is done to check the PR interval.

Echocardiography changes management when carditis is suspected. A physical exam alone can miss valve abnormalities that count as a major criterion under current guidelines and that directly affect how long prophylaxis should continue. In Bangkok’s private medical system, echocardiography is accessible and referral is straightforward.

At Doctor Bangkok, the initial assessment, blood tests, and ECG can all be done on the same day. If an echocardiogram is needed, referral is arranged directly. Patients who arrive with an existing rheumatic fever diagnosis are seen for prophylaxis review, cardiac history documentation, and ongoing care planning.

Rheumatic fever treatment: antibiotics, anti-inflammatory therapy, and follow-up

Treatment has three goals: clear the strep infection, reduce the acute inflammation, and prevent future strep infections from triggering another episode.

Acute rheumatic fever treatment protocol

Even if the throat looks normal, clearing the strep infection comes first. A ten-day course of oral amoxicillin or a single penicillin injection is standard. Group A streptococcus has not developed penicillin resistance, which is genuinely useful. For confirmed penicillin allergy, azithromycin or a cephalosporin may be used depending on the type of reaction.

For arthritis without heart involvement, aspirin or naproxen works well. A rapid, dramatic response to aspirin is something clinicians often notice in rheumatic fever, though it is not a formal criterion. When carditis is confirmed, corticosteroids are often added, particularly in moderate to severe cases. The evidence for corticosteroids improving long-term valve outcomes is rated as moderate, so they are used for significant cardiac involvement rather than routinely.

Physical rest during the acute phase matters, especially with active heart inflammation. How much rest is needed depends on the degree of cardiac involvement and whether inflammatory markers are settling.

Follow-up includes serial blood tests to guide treatment duration, repeat cardiac assessment, and planning for long-term prophylaxis. Arthritis typically resolves within weeks. Carditis can take longer to settle, and echocardiographic monitoring continues beyond the acute phase.

Rheumatic fever prophylaxis: preventing recurrence with long-term penicillin

Secondary prophylaxis is the most important part of long-term management. Every subsequent strep throat, left untreated, can trigger another episode and add more valve damage. Preventing recurrences is not a minor add-on. It is the central long-term intervention.

Benzathine penicillin G, given by intramuscular injection every three to four weeks, is the most reliable approach. Oral penicillin twice daily is an option for motivated patients, but consistent daily adherence over years is genuinely harder to sustain. The injectable form removes that variable and is preferred by WHO and American Heart Association guidelines for patients at meaningful risk.

How long prophylaxis continues depends on whether carditis occurred and whether it left lasting valve damage. The WHO recommends five years from the last episode, or until age twenty-one, whichever is longer, for patients without carditis. For carditis without residual valve disease, ten years or age twenty-one. For persistent valve damage, at least ten years or until age forty, with lifelong continuation considered when valve disease is haemodynamically significant.

For expats in Bangkok with a history of rheumatic fever, accessing regular penicillin injections through a private clinic is straightforward. The more common barrier is not the medication. It is not knowing whether carditis occurred, whether prophylaxis was ever completed, or what the current valve status looks like. A clinical review with echocardiography is the right starting point.

Penicillin allergy is worth reviewing critically. Many patients report an allergy based on a childhood rash that was more likely viral than a true drug reaction. Formal allergy assessment expands the prophylaxis options available and may be worth arranging when the reported allergy is the main barrier to optimal treatment. When a true allergy is confirmed, sulfadiazine or erythromycin are used as alternatives.