The Link Between Rheumatic Fever and Heart Disease

Rheumatic fever is one of the clearest examples in medicine of an ordinary infection triggering lasting damage to the heart. A strep throat that goes untreated or inadequately treated can set off an immune reaction that attacks heart valve tissue, and repeated episodes can scar those valves badly enough to cause lifelong heart disease. Globally, an estimated 33 million people live with rheumatic heart disease, and the condition remains a leading cause of cardiovascular death in young adults across much of the developing world.

How a Throat Infection Reaches the Heart

The chain of events begins with group A streptococcus, the bacterium behind common strep throat and some skin infections.¹ In most people, the immune system clears the infection and moves on. In a small percentage, though, the body’s immune response goes awry. Certain proteins on the surface of group A strep, particularly the M protein, share structural features with proteins found in human heart tissue. The immune system, primed to destroy the bacterium, begins attacking heart cells that look similar. Researchers call this phenomenon molecular mimicry, and it is central to how rheumatic fever damages the heart.²

Work with T-cell clones taken directly from inflamed heart tissue has confirmed this crossover. Immune cells isolated from the hearts of patients with rheumatic heart disease recognized both streptococcal M protein fragments and human heart proteins simultaneously.³ In other words, the immune cells could not tell the difference between the invading bacterium and the patient’s own heart. Once these self-reactive immune cells take up residence in heart valve tissue, they release inflammatory signals that tilt the local immune environment toward chronic damage, driving progressive and sometimes permanent valve injury.⁴

Why the Mitral Valve Takes the Worst Hit

Rheumatic heart disease overwhelmingly targets the mitral valve, the structure that controls blood flow between the left atrium and left ventricle. In a necropsy study of over 500 patients with severe chronic valve disease, the hallmark lesions of rheumatic inflammation were found almost exclusively in patients whose mitral valves were affected, sometimes along with other valves but rarely without it.⁵ The characteristic signs of active rheumatic inflammation include inflammatory cell clusters called Aschoff bodies and distinctive modified cells called Anitschkow cells, both of which pathologists recognize as markers of rheumatic valve damage.⁶

What makes rheumatic heart disease particularly insidious is that valve damage keeps progressing even after the acute inflammation dies down. The initial immune attack triggers scarring and fibrotic thickening of the valve leaflets. Those thickened, stiffened leaflets distort blood flow, and the resulting turbulence puts further mechanical stress on the valve. That stress, in turn, activates more scarring.⁷ It becomes a self-perpetuating cycle: inflammation begets structural change, structural change begets abnormal blood flow, and abnormal blood flow begets more structural change.⁸ Each recurrence of acute rheumatic fever accelerates the process, which is why prevention of repeat episodes is so critical.

Not Just Throat Infections

For decades, the standard teaching was that only strep throat could trigger rheumatic fever. Skin infections were considered bystanders. That picture has shifted. Research in New Zealand, a country with stubbornly high rheumatic fever rates among Māori and Pacific Peoples, found that skin infections caused by group A strep were independently associated with acute rheumatic fever, with a risk roughly comparable to that of throat infections.⁹ Strain-typing studies in the same population found a high proportion of strep strains traditionally associated with skin disease, further supporting the idea that pyoderma plays a role in triggering rheumatic fever.¹⁰

This matters because prevention strategies have historically focused on identifying and treating strep throat. If skin infections are also a trigger, then programs that screen only for sore throats will miss some of the children at risk. Only a relatively small number of strep strains appear capable of inducing rheumatic fever, and which strains predominate varies between high-income and low-income countries.¹¹

Who Gets Rheumatic Heart Disease and Why

The global burden is starkly uneven. A landmark study published in the New England Journal of Medicine estimated roughly 33 million cases of rheumatic heart disease worldwide as of 2015, with the highest rates in Oceania, South Asia, and central sub-Saharan Africa. Although age-adjusted mortality fell by about 48% between 1990 and 2015, that progress was concentrated in wealthier regions.¹² More recent modeling suggests that without intervention, some regions in sub-Saharan Africa and Southeast Asia will see worsening outcomes through at least 2041.¹³

Poverty is the dominant thread connecting the populations most affected. Household crowding is consistently one of the strongest risk factors, because it creates ideal conditions for strep to spread person to person.¹⁴ A case-control study from New Zealand found that crowding nearly quadrupled the odds of acute rheumatic fever, and barriers to primary health care doubled them.¹⁵ In Uganda, overcrowding and distance from the nearest health center interacted so that the farther a family lived from a clinic, the more dangerous crowding became.¹⁶ The decline of rheumatic fever in wealthy nations during the twentieth century had as much to do with improved housing, nutrition, and sanitation as it did with the arrival of penicillin.¹⁷

Genetic Susceptibility

Not everyone who gets strep throat develops rheumatic fever, and only some people with rheumatic fever go on to have heart damage. Part of that variability is genetic. Research since the 1980s has pointed to the human leukocyte antigen (HLA) region on chromosome 6, a stretch of DNA that helps the immune system distinguish self from non-self. Specific variants in the HLA-DQA1 and HLA-DQB1 genes, along with genes in the immunoglobulin heavy chain region on chromosome 14, have been linked to susceptibility.¹⁸

A genome-wide study comparing South Asian and European patients identified a novel susceptibility signal in a different part of the HLA complex, the class III region. This association was strong and replicated in both ethnic groups, suggesting a shared genetic vulnerability that partly explains why earlier studies focusing on other HLA regions produced inconsistent results.¹⁹ Separately, certain HLA-B alleles have been found at higher frequencies among patients with rheumatic heart disease compared to controls.²⁰ None of these genetic variants alone cause the disease; they appear to modulate how vigorously the immune system reacts to strep, and environmental factors like poverty and crowding amplify or dampen that risk.

How Rheumatic Fever and Heart Damage Are Diagnosed

Acute rheumatic fever has been diagnosed using a clinical framework called the Jones criteria since the 1940s, but the most recent revision in 2015 made significant changes. For the first time, the criteria distinguished between low-risk and moderate-to-high-risk populations, using different diagnostic thresholds for each. In communities where rheumatic fever is common, the bar for diagnosis was deliberately set lower to catch more cases.²¹

The biggest practical change was the inclusion of subclinical carditis, heart inflammation detected by echocardiography but not apparent on physical exam, as a major diagnostic criterion.²² This was overdue. Earlier research had warned that relying on older World Health Organization echocardiographic criteria could miss up to three quarters of children with subclinical rheumatic heart disease.²³ In high-prevalence regions, echocardiography is now recommended for all suspected cases, because catching early valve changes before symptoms appear gives patients the best chance of preventing progression.

Screening programs using portable echocardiography have expanded in recent years, but distinguishing early rheumatic valve damage from the trivial valve leakage that healthy children sometimes have remains a real challenge. A study of healthy students found that small amounts of valve regurgitation fall within normal range, meaning that screening criteria need to be specific enough to avoid overdiagnosis while sensitive enough to catch genuine disease.²⁴

Prevention at Two Levels

Preventing rheumatic heart disease works on two fronts. The first, called primary prevention, is simply treating strep throat with antibiotics before rheumatic fever can develop.²⁵ A meta-analysis of trials found that antibiotic treatment of strep pharyngitis reduced the risk of developing rheumatic fever by about 70% overall, and penicillin specifically cut the risk by 80%.²⁶ This sounds straightforward, but it requires that strep throat is recognized and treated promptly, which depends on access to health care that many at-risk populations lack.

The second front, secondary prevention, targets people who have already had one episode of rheumatic fever or who already have early heart damage. Regular injections of long-acting penicillin, typically every four weeks for years, prevent recurrent strep infections and therefore prevent the repeated bouts of immune activation that progressively destroy valves. This approach reduces recurrences by roughly 87 to 96%.²⁷ A large randomized trial in Australia and New Zealand demonstrated just how much this matters at the earliest stage of disease: among children with latent rheumatic heart disease, those receiving penicillin prophylaxis showed echocardiographic progression in less than 1% of cases over two years, compared with about 8% of those receiving no prophylaxis.²⁸

Despite the clear evidence, adherence to secondary prophylaxis is notoriously poor. Fear of injection pain, feeling well between doses, forgetting scheduled appointments, and a lack of understanding of the disease process all contribute.²⁹ A monthly intramuscular injection for potentially a decade or more is a heavy ask, especially for children and adolescents. Ironically, patients with milder disease are often the worst adherers, because they feel healthy and see no immediate reason to keep coming back for painful shots.

When Valves Need Surgery

When valve damage progresses far enough, surgery becomes the only option. For patients with mitral stenosis, where the valve narrows and restricts blood flow, a procedure called percutaneous balloon valvuloplasty can widen the opening without open-heart surgery. For patients with severe mitral regurgitation, where the valve leaks backward, the choice is between repairing the native valve and replacing it entirely.³⁰

Valve repair, when feasible, has clear advantages. A pooled analysis of studies comparing the two approaches in rheumatic patients found that those who had valve repair had better long-term survival and fewer valve-related complications overall. The tradeoff is a higher rate of reoperation, because repaired rheumatic valves can deteriorate again over time.³¹ The harsh reality is that valve repair requires specialized surgical expertise that is scarce in exactly the regions where rheumatic heart disease is most common. Many patients in sub-Saharan Africa and South Asia who need surgery simply do not have access to it.

Rheumatic Heart Disease During Pregnancy

Pregnancy puts extra demands on the heart, and for women with rheumatic valve damage, those demands can be dangerous. A systematic review of studies from sub-Saharan Africa found that heart failure developed in at least 13% and up to 36% of pregnant women with rheumatic heart disease. Preterm delivery was the most common obstetric complication, occurring in anywhere from 5 to 35% of pregnancies. Cardiac deaths were reported in the majority of the studies reviewed, and very few of the women received any valve intervention during or before pregnancy.³² In settings where pre-pregnancy counseling and cardiac monitoring are available, outcomes are better, but many women in endemic areas are not diagnosed until they become symptomatic during pregnancy.

Atrial Fibrillation and Stroke Risk

As rheumatic valve damage worsens, the left atrium often enlarges, which predisposes to atrial fibrillation. Patients with rheumatic heart disease and atrial fibrillation have long been assumed to face an especially high stroke risk, and anticoagulation with drugs like warfarin is routinely recommended.³³ Interestingly, though, a large global registry study of over 15,000 patients with atrial fibrillation found that those who had rheumatic heart disease were actually younger, more likely to be female, and had lower conventional stroke-risk scores than non-rheumatic patients. In that dataset, mitral stenosis itself was not independently associated with higher stroke risk once other factors were accounted for.³⁴ This does not mean anticoagulation is unnecessary for these patients, but it does suggest that the conventional wisdom about rheumatic mitral stenosis carrying an inherently extreme stroke risk may be more nuanced than once thought. Ongoing trials are testing whether newer anticoagulants perform better than warfarin in this population.

The Economics of Prevention

Rheumatic heart disease is one of those conditions where an ounce of prevention is genuinely worth a pound of cure, and the numbers bear that out. An analysis of a prevention program in Cuba that focused on identifying and treating strep throat in children found that the program averted over 230 cases of acute rheumatic fever and over 100 cases of rheumatic heart disease in a cohort of roughly 274,000 at-risk children. The total medical costs averted exceeded $7.8 million, dwarfing the program’s investment of about $203,000. In every simulation the researchers ran, the prevention program saved both money and lives compared to doing nothing.³⁵ The challenge is not the math. It is building and sustaining health systems in low-resource settings where crowding, poverty, and limited infrastructure conspire to keep strep circulating and children undiagnosed.

Vaccine Prospects

The ultimate solution would be a vaccine against group A strep, which would prevent rheumatic fever at the source. Several vaccine candidates exist, some based on the M protein itself and others on conserved antigens shared across strep strains. Combination vaccines containing multiple protective antigens have shown promise in animal models, and a few have entered early-stage human trials.³⁶ Progress has been slow, though. The same molecular mimicry that makes rheumatic fever possible in the first place creates a safety concern for any vaccine built around strep surface proteins: researchers need to be confident that a vaccine will not accidentally trigger the autoimmune response it is meant to prevent. Regulatory caution around this risk, combined with limited commercial incentive (the burden falls overwhelmingly on poor populations), has kept development timelines long. No licensed vaccine exists yet, and one is unlikely to reach widespread use for at least another decade.