Endocarditis: The Heart Valve Infection Behind the Fever That Will Not Quit
Last updated September 4, 2026.
Endocarditis is an infection of the heart's inner lining, almost always involving a valve, and it is the diagnosis behind a specific, missable story: weeks of low fever, bone-deep exhaustion, night sweats, and vague decline in someone with a valve problem, a prosthetic valve or device, a history of the infection, or injecting-drug exposure. It is uncommon and serious: the infection grows as vegetations that damage the valve and can seed strokes and other emboli. It is also very treatable when found: weeks of targeted intravenous antibiotics, and surgery for the valves that need it. The danger is the weeks spent being called a virus.
The story it tells
The classic presentation is nonspecific on purpose: persistent or recurring fever, exhaustion out of proportion, drenching night sweats, aching, poor appetite, and sometimes new shortness of breath or a new heart murmur. The telltale extras appear in some: tiny painless spots, small painful nodules on the fingers or toes, splinter lines under the nails, and, in the embolic complications, sudden neurologic or limb symptoms. The risk factors concentrate the suspicion: known valve disease including bicuspid aortic valves, prosthetic valves and pacemakers, previous endocarditis, congenital heart disease, injecting drug use, recent invasive dental or surgical work, and long-term catheters.
Weeks of fever, night sweats, and exhaustion in someone with a valve condition is endocarditis until blood cultures say otherwise. Cultures before antibiotics; echo after.
Start a free AI doctor consult →The diagnosis that should not wait
The test sequence is fixed because it works: blood cultures, several sets drawn before any antibiotic, find the organism in the large majority; an echocardiogram, often the transesophageal kind, sees the vegetation and the valve damage. Every day of untreated growth is more valve destruction, which is why weeks of unexplained fever in a person with a valve history is a cultures-first situation, and why starting blind antibiotics before the cultures are drawn is the error that muddies the diagnosis. Treatment is then four to six weeks of intravenous antibiotics matched to the organism, with heart surgery for the valves that are failing, leaking badly, or throwing emboli.
Prevention, for the people who need it
For the highest-risk group, prosthetic valves, previous endocarditis, certain congenital and transplant-valve situations, prevention has a name and a routine: antibiotic prophylaxis before specific dental procedures, meticulous dental and skin hygiene as the daily work, and no injecting-drug exposure. For everyone else, the prevention is the unremarkable kind: teeth kept healthy, skin infections treated, and the knowledge, if you carry a valve condition, that a fever lasting more than a few days is not yours to wait out.
- Weeks of fever, exhaustion, and night sweats plus a valve history is the pattern. Bicuspid valve, prosthetic valve, device, previous endocarditis, or injecting exposure: any of them with a persistent fever earns blood cultures now.
- Cultures before antibiotics. The blood cultures drawn before the first antibiotic dose find the organism; blind antibiotics first can erase the evidence and delay the diagnosis by weeks.
- Prophylaxis is for a defined high-risk group. Prosthetic valves, previous endocarditis, certain congenital and transplant valves: antibiotic cover before specific dental procedures, plus teeth and skin kept healthy as the daily work.
If you are weighing the risks and benefits of any medicine mentioned here, our overview of how medicines are tested and monitored for safety explains what those conversations are built on.
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Common questions
What is endocarditis?
Infection of the heart's inner lining, almost always a valve, where bacteria grow as vegetations that damage the valve and can seed emboli to the brain and limbs. It is uncommon, serious, and very treatable when found: weeks of targeted intravenous antibiotics, and surgery for the valves that need it.
What are the symptoms?
Persistent or recurring fever, exhaustion out of proportion, drenching night sweats, aching, and poor appetite, sometimes with new breathlessness or a new murmur. The extras in some: tiny painless spots, painful nodules on fingers or toes, splinter lines under the nails, and sudden neurologic or limb symptoms from emboli.
Who is at risk?
People with known valve disease including bicuspid aortic valves, prosthetic valves, pacemakers and devices, previous endocarditis, certain congenital heart disease, injecting drug use, recent invasive dental or surgical work, and long-term catheters.
How is it diagnosed?
Blood cultures, several sets drawn before any antibiotic, find the organism in the large majority, and an echocardiogram, often transesophageal, sees the vegetation and valve damage. Starting blind antibiotics before the cultures is the error that delays the diagnosis.
What is the treatment?
Four to six weeks of intravenous antibiotics matched to the cultured organism, with heart surgery for valves that are failing, leaking badly, uncontrolled, or throwing emboli. Outcomes are best when treatment starts before the valve is destroyed, which is the argument for early testing.
Can endocarditis be prevented?
For the highest-risk group, prosthetic valves, previous endocarditis, certain congenital and transplant-valve situations: antibiotic prophylaxis before specific dental procedures, meticulous dental and skin hygiene, and no injecting-drug exposure. For everyone with a valve condition: a fever lasting more than a few days is not yours to wait out.