Cat-scratch disease is an infection that usually starts after a scratch or bite from a kitten or cat. Early symptoms of cat-scratch disease often include a small bump at the scratch site and tender, swollen lymph nodes near it, with mild fever or fatigue. Most people with cat-scratch disease get better on their own over a few weeks to a few months, and serious complications are uncommon. Children and teens are affected most often, but adults can get it too. Treatment is usually supportive, and some people with cat-scratch disease may receive antibiotics if symptoms are more severe or prolonged.
Overview
Cat-scratch diseaseSymptoms
Cat-scratch disease often starts with a small bump or blister where a scratch or bite happened. Within 1–3 weeks, nearby lymph nodes swell and feel tender, with fever, fatigue, and headache. Some develop eye redness or, rarely, more serious problems.
Outlook and prognosis
Most people with cat-scratch disease recover fully within weeks to a few months, especially with rest and, when needed, antibiotics. Swollen nodes can stay tender or slightly enlarged for a while but usually settle. Severe complications are uncommon and are monitored closely.
Causes and risk factors
Cat-scratch disease is caused by Bartonella henselae from cats, via scratches, bites, or flea-contaminated claws. Risk rises with kittens, rough play, flea infestations, outdoor cats, and broken skin; children and immunocompromised people are vulnerable. No genetic risk is known.
Genetic influences
Genetics plays a minimal role in cat-scratch disease, which is caused by a bacterial infection. Most risk depends on exposure to infected cats and breaks in the skin. Rare genetic immune differences may influence severity or recovery, but aren’t the primary driver.
Diagnosis
Diagnosis of Cat-scratch disease is mainly based on cat exposure and typical swollen lymph nodes near a scratch. Blood tests (Bartonella serology) or PCR from a lymph node can confirm and rule out mimics. Imaging is reserved for complications.
Treatment and drugs
Treatment for cat-scratch disease focuses on easing symptoms and helping swollen lymph nodes heal. Many people recover with rest, pain relief, and warm compresses; doctors may add azithromycin or similar antibiotics for prolonged lymph node swelling or severe infection. Those with weakened immunity often need antibiotic therapy and close follow-up.
Symptoms
Cat-scratch disease often starts with a small bump or blister where the skin was scratched, followed days later by a tender, swollen lymph node nearby. Symptoms vary from person to person and can change over time. Early symptoms of cat-scratch disease may also include a low fever, tiredness, and headache, and most people improve within a few weeks. People with weaker immune systems may have stronger or longer-lasting symptoms.
A small, red bump or fluid-filled blister can form where the scratch or bite happened. It may be tender and can crust over as it heals.
One or more lymph nodes close to the scratch become swollen and sore. Under the arm, neck, or jaw are common spots. This is a hallmark of cat-scratch disease.
A mild fever may develop alongside swollen glands. It often comes and goes for several days. Fever is common with cat-scratch disease.
Many feel unusually tired or low on energy. Rest can help, but fatigue may last for days to weeks.
How people usually first notice Cat-scratch disease?
Many people first notice cat-scratch disease a week or two after a playful scratch or bite from a kitten or cat, when a small bump or blister develops at the scratch site that doesn’t heal as quickly as expected. Soon after, one or more nearby lymph nodes—often in the armpit, elbow crease, or neck—become swollen, tender, and sometimes warm, and some people feel tired, get a mild fever, or have a headache. For most, these first signs of cat-scratch disease follow a clear timeline: recent cat contact, a local skin change, then swollen nodes on the same side of the body.
Types of Cat-scratch disease
Cat-scratch disease is an infection that often starts after a scratch or bite from a kitten or cat and can affect people differently in day-to-day life. Some mostly notice a sore bump and a tender, swollen lymph node near the scratch, while others feel more run-down with fever and fatigue. Less commonly, it can involve the eye or the nervous system, which may change how symptoms show up and how it’s treated. Symptoms don’t always look the same for everyone.
Typical lymph node form
This common type causes a small skin bump at the scratch site followed by painful, swollen lymph nodes nearby. Fever, tiredness, and headache can develop over days to weeks.
Eye involvement
When the bacteria reach the eye, people may develop red, irritated eyes and blurry vision. Light sensitivity or floaters can appear, and one eye is usually affected.
Nervous system involvement
A rare variant inflames the brain or nerves and can cause severe headache, confusion, or seizures. Recovery usually occurs, but it may take weeks and needs urgent medical care.
Bone or liver/spleen involvement
In some cases, deeper infections affect bones or cause tender belly pain from inflamed liver or spleen. Fevers can be higher, and imaging tests often help confirm the diagnosis.
Skin-only presentation
A few people mainly have a small, nonhealing bump or blister at the scratch site with minimal lymph node swelling. It can be itchy or mildly sore but often clears on its own.
Immunocompromised presentation
People with weakened immune systems can develop widespread or more severe disease. Clinicians often describe them in these categories: skin, eye, organ, or nervous system involvement, which guides treatment.
What genetics can tell you about symptoms
Some people with cat-scratch disease who carry variants in immune genes like HLA or IL-10 may have stronger swelling of lymph nodes, fever, or fatigue because their immune response runs “hotter.” Rare changes in genes affecting blood vessels can raise the chance of eye or neurologic complications.
Causes and risk factors
Cat-scratch disease is caused by a type of bacteria called Bartonella henselae that spreads from cats to people. It usually spreads through a scratch or bite, or when cat saliva touches broken skin or the eye. Risk factors for cat-scratch disease include close contact with kittens, rough play that leads to scratches, and exposure to flea-infested cats, especially in warm climates. People with weakened immunity, like after an organ transplant or with HIV, face higher risk of severe illness, while genetics has no clear role. Some risks are modifiable (things you can change), and others are non-modifiable (things you can’t).
Environmental and biological risk factors
Cat-scratch disease happens after bacteria carried by cats get into the body, usually through a scratch or bite. Doctors often group risks into internal (biological) and external (environmental). Here are the main environmental and biological factors that can raise the chance of cat-scratch disease. Knowing these can help you respond promptly if early symptoms of cat-scratch disease appear.
Bacteria in cat saliva and under the claws can enter through broken skin. Deeper or multiple scratches can raise the chance of cat-scratch disease. Even small nicks can be a route in.
Kittens are more likely than adult cats to carry the bacteria. Frequent play with young cats increases exposure. This can raise the risk of cat-scratch disease.
Fleas spread the bacteria between cats, and flea dirt can contaminate claws. Being around flea-infested cats increases the chance of exposure. Homes or shelters with flea problems carry higher risk.
Cat saliva or contaminated fingers that touch the eye can introduce the bacteria. This can lead to swollen lymph nodes near the ear and eye. Eye contact with contaminated material can be a route of infection.
Genetic risk factors
Cat-scratch disease does not have a genetic cause. Most people’s genes do not change their chance of getting infected, but inherited immune problems can influence how severe it becomes. Some risk factors are inherited through our genes. Genes themselves do not change the early symptoms of cat-scratch disease, but they may shape the body’s response.
No clear inheritance: Cat-scratch disease does not follow a family inheritance pattern. It is not passed from parent to child through DNA. Family history alone does not raise genetic risk.
Inherited immune conditions: People born with certain immune system disorders face a higher chance of severe or unusual cat-scratch disease. These rare conditions reduce the body’s ability to control the bacteria. Carrying a genetic change doesn’t guarantee the condition will appear.
No single risk gene: Research has not identified a consistent gene tied to cat-scratch disease. Some studies suggest immune response genes could affect susceptibility, but results are not consistent. There is no routine genetic marker used in care.
Ancestry not determinant: Cat-scratch disease occurs across all ancestries, with no proven genetic risk linked to ethnicity. Published data have not shown reliable differences by heritage.
Genetic testing role: Testing is not needed for typical cat-scratch disease. It may be considered only when a doctor suspects an inherited immune problem because of recurrent, severe, or unusual infections.
Lifestyle risk factors
Cat-scratch disease is usually acquired through everyday interactions with cats, especially kittens. The main lifestyle risk factors for Cat-scratch disease relate to how you play with, care for, and clean up after cats. Adjusting these habits can lower your chance of scratches or saliva exposure and reduce infection risk.
Wrestling or letting cats bite and scratch increases skin breaks where bacteria can enter. Using toys and keeping hands away from claws and teeth lowers risk.
Kittens carry Bartonella more often and scratch unpredictably. Gentle, supervised handling reduces sudden scratches.
Touching eyes or skin after cat contact can transfer bacteria. Washing hands or using sanitizer after play or litter box duties reduces spread.
Not immediately washing scratches or bites lets bacteria persist in the skin. Rinsing with soap and water and applying antiseptic lowers infection chances.
Risk prevention
Simple habits around cats can lower the chance of getting cat-scratch disease. Prevention is about lowering risk, not eliminating it completely. There’s no vaccine, so everyday steps, flea control, and quick care for scratches matter most. If you live with a medical condition that weakens immunity, extra caution is especially important.
Avoid rough play, especially with kittens, to prevent scratches. Fewer scratches mean a lower risk of cat-scratch disease. Teach children to stroke, not wrestle.
Keep your cat’s nails short to reduce deep scratches. Ask a vet or groomer if trimming at home is hard. This lowers the chance that a scratch leads to cat-scratch disease.
Wash any bite or scratch right away with soap and water. Use an antiseptic, then keep it clean and dry. Don’t let a cat lick your open skin.
Use vet-recommended flea prevention on your cat and treat the home environment if needed. Controlling fleas lowers how often cats carry the germ that causes cat-scratch disease. Check regularly and keep treatments up to date.
Transmission
Cat-scratch disease is usually passed to people through a scratch or bite from a cat—often a playful kitten—and sometimes when cat saliva gets into broken skin or the eye. The bacteria are carried by cats and can be on their claws if contaminated by flea droppings, so fleas spread the germ between cats, and a cat can then pass it to humans. You don’t catch cat-scratch disease from casual contact, and it doesn’t spread from person to person. In simple terms, how cat-scratch disease spreads is through direct contact that breaks the skin, so avoiding rough play and keeping claws trimmed and fleas controlled lowers the risk. It isn’t considered highly contagious, but people with weakened immune systems should be extra careful because even a small scratch can lead to infection.
When to test your genes
Cat-scratch disease is an acquired infection, so genetic testing isn’t routinely helpful. Consider testing only if you have unusual, severe, or recurrent symptoms suggesting an underlying immune or inherited susceptibility, or if multiple close relatives have similar infections. Talk with your clinician; targeted immune or genetic tests may guide personalized care.
Diagnosis
Swollen, tender lymph nodes near a recent cat scratch or bite can be puzzling, especially when the scratch has healed. Doctors usually begin by asking about contact with cats (especially kittens) and examining the skin and nearby lymph nodes for patterns that fit Cat-scratch disease. Lab tests help confirm what the exam suggests and rule out look-alike infections. If you’re wondering about the diagnosis of Cat-scratch disease, most people are diagnosed based on history, exam findings, and targeted tests when needed.
Clinicians ask about recent scratches or bites, cat exposure, and a small bump at the injury site. They check for one-sided swollen lymph nodes near the scratch and mild fever or fatigue. This pattern often points toward Cat-scratch disease.
A blood test looks for antibodies to Bartonella henselae. A positive result supports Cat-scratch disease, especially when timing and symptoms fit. Early tests can be negative, so repeat testing may be considered if suspicion remains.
Molecular tests can look for Bartonella DNA in a lymph node sample or tissue. PCR is often used when the diagnosis is unclear or complications are present. A positive result can help confirm Cat-scratch disease.
An ultrasound can show if a lymph node has fluid that suggests pus. This helps guide drainage and can ease pain. It also supports the overall picture when evaluating Cat-scratch disease.
Stages of Cat-scratch disease
Cat-scratch disease does not have defined progression stages. It usually begins with a small bump or blister where the scratch happened, then nearby lymph nodes become swollen and tender, and most people get better over a few weeks without moving through set phases; rarer eye, liver, or nerve problems are complications, not stages. Doctors often diagnose it by your story of cat exposure and an exam, looking for early symptoms of cat-scratch disease such as a tender lymph node and mild fever; blood tests or imaging may be used if the picture isn’t clear. Different tests may be suggested to help confirm the infection or rule out other causes when symptoms don’t follow the typical pattern.
Outlook and prognosis
Fevers and tender lymph nodes usually fade within a few weeks to a few months for most people with cat-scratch disease, and energy gradually returns to normal. Many people find that symptoms settle without specific treatment, though a short course of antibiotics is sometimes used to speed recovery or prevent complications. People with very weak immune systems—such as those on chemotherapy, high-dose steroids, or with advanced HIV—face a higher risk of more serious infection spreading to the liver, spleen, eye, or nervous system, so doctors monitor them closely.
Looking at the long-term picture can be helpful. In otherwise healthy children and adults, lasting problems are uncommon, and once the infection clears, it usually does not come back. Rare complications include bone or joint infection, eye inflammation that can affect vision, and, very rarely, brain or spinal cord involvement; these call for prompt care but are treatable in many cases. Death from cat-scratch disease is extremely rare and is typically linked to severe immune compromise or delayed treatment of widespread infection.
Understanding the prognosis can guide planning and day-to-day choices during recovery. If early symptoms of cat-scratch disease like a blister at the scratch site, fever, or a painful swollen node are getting worse after a week or two, or new symptoms appear, it’s worth checking in with a clinician. With ongoing care, many people maintain normal routines, returning to school or work as fatigue lifts and tenderness eases. Talk with your doctor about what your personal outlook might look like, especially if you have a condition or medication that affects your immune system.
Long-term effects
For most people, cat-scratch disease clears on its own, but a small number have effects that linger or show up later. You might notice swollen lymph nodes or tiredness that lasts longer than expected, sometimes for months. Long-term effects vary widely, and most are uncommon but worth knowing about. While early symptoms of cat-scratch disease often fade in a few weeks, rare complications can involve the eyes, brain, liver, spleen, or bones.
Swelling near the original scratch can last for weeks to months. Nodes may stay firm or tender even after other symptoms fade. Some develop draining or slow-to-heal lumps.
Low energy can linger after the fever and soreness are gone. Many describe feeling run-down for several weeks. This usually improves gradually over time.
If the infection affects the eye, vision can blur or dim for a time. Most people recover well, but a small number have lasting blind spots or mild vision changes.
Rarely, brain irritation can cause headaches, confusion, or seizures during the illness. Most recover fully, though a few may have lingering attention or memory issues.
How is it to live with Cat-scratch disease?
Living with cat-scratch disease is usually a short, uncomfortable detour rather than a long road; most people feel tired and sore where the scratch or bite happened, and nearby lymph nodes can swell and ache for weeks. Daily life may slow down with low-grade fevers, fatigue, and tenderness that make lifting, turning the neck, or workouts uncomfortable, though over-the-counter pain relief and rest often help. For people around you, the main effect is practical—someone may need to help with chores or pet care temporarily—but routine contact is safe because it doesn’t spread person to person. Pet owners often feel a mix of worry and guilt; simple steps like gentle play, nail trimming, flea control, and handwashing let you stay close to your cat while you heal and prevent future scratches.
Treatment and drugs
Cat-scratch disease treatment focuses on easing symptoms and helping your body clear the infection, which for many people happens on its own over a few weeks. Mild cases often need only supportive care like rest, fluids, and over-the-counter pain or fever reducers, while more bothersome symptoms or large, tender lymph nodes may be treated with a short course of antibiotics such as azithromycin to speed recovery. Doctors sometimes drain very swollen lymph nodes to relieve pressure and pain, but this is decided case by case. People with weakened immune systems, severe eye or nerve involvement, or infection that spreads beyond the lymph nodes usually need prescription antibiotics for longer and closer follow-up. Your doctor can help weigh the pros and cons of each option.
Non-drug treatment
Many people with Cat-scratch disease recover with time and simple self-care, but the swollen lymph nodes and fatigue can make daily tasks uncomfortable. Non-drug treatments often lay the foundation for comfort and recovery while your immune system does the heavy lifting. Paying attention to early symptoms of Cat-scratch disease—like a tender lump near a recent scratch, mild fever, or feeling run down—can help you act early with supportive steps. Prevention at home, plus practical comfort measures, usually go a long way.
Wash any scratch or bite right away with soap and running water. Rinse well, pat dry, and keep it clean to lower the chance of skin infection.
Apply a warm, damp cloth to tender lymph nodes for 10–15 minutes several times a day. This can ease soreness and may help swelling settle without squeezing the area.
Prioritize sleep and light activity while fever or tiredness linger. Adequate fluids support your body’s recovery and help prevent dehydration.
Avoid heavy lifting or sports that strain areas with swollen nodes, like the armpit or groin. Gradually return to normal routines as pain and energy improve.
Your genes may have an impact on how drugs work for you
Some antibiotics used for cat-scratch disease work differently from person to person because our genes affect how fast we process and clear medicines. Pharmacogenetic testing, when available, can guide dosing or drug choice to improve effectiveness and reduce side effects.
Pharmacological treatments
Most people with Cat-scratch disease get better on their own, but antibiotics can shorten how long swollen lymph nodes last and may lower the chance of complications. Doctors often start with azithromycin, and choose other options if the illness is severe or affects the eyes, liver, or nervous system. First-line medications are those doctors usually try first, based on safety and how well they work. Antibiotics may be offered even when early symptoms of Cat-scratch disease seem mild, especially if swelling is painful or slow to improve.
Often the first choice to speed recovery and shrink tender lymph nodes in Cat-scratch disease. Usually well tolerated and safe for many, including during pregnancy. It is taken for a short course.
Used when Cat-scratch disease involves the eye (neuroretinitis) or nervous system, sometimes for a longer course. Doctors may pair it with another antibiotic in severe cases. It can increase sun sensitivity and isn’t ideal during pregnancy.
Commonly combined with doxycycline for complicated Cat-scratch disease (such as eye, liver, or neurologic involvement). It has many drug interactions, so your care team will review other medicines carefully. Urine and tears can turn orange while taking it.
An alternative if macrolides or tetracyclines aren’t suitable, and it’s often used in children. It can cause rash in people with sulfa allergy. Staying well hydrated may help reduce kidney-related side effects.
Genetic influences
For most people, genes have little influence on who gets cat-scratch disease; close contact with an infected cat is the main driver. It’s natural to ask whether family history plays a role. When more than one person in a home develops cat-scratch disease, it’s almost always due to shared exposure—like the same playful kitten—rather than shared DNA. That said, differences in the immune system can affect how the illness plays out; rare inherited immune conditions, or medicines that weaken immunity, can make symptoms more severe or longer-lasting. There’s no routine genetic testing or specific gene to check, and genetic risk for cat-scratch disease is considered low. If a known inherited immune disorder runs in your family, ask your doctor about extra care around scratches and bites.
Is Cat-scratch disease genetic?
Genetics plays a minimal role in cat-scratch disease, which is caused by a bacterial infection. Most risk depends on exposure to infected cats and breaks in the skin. Rare genetic immune differences may influence severity or recovery, but aren’t the primary driver.
Pharmacogenetics—how genetics influence drug effects
When treatment is needed for cat-scratch disease, doctors usually choose antibiotics, and a few inherited traits can shape safety and drug choice. For example, people with a genetic condition called G6PD deficiency have a higher risk of red blood cell breakdown with certain sulfonamide antibiotics such as trimethoprim–sulfamethoxazole, so other options may be preferred or extra monitoring used. Macrolide medicines like azithromycin can affect heart rhythm, and those with an inherited long QT syndrome may face extra risk of dangerous rhythm changes, so clinicians pay close attention to your personal and family history and any other medicines that can affect heart rhythm. Most other commonly used choices, such as doxycycline or rifampin for more complex infections, don’t have routine, proven pharmacogenetic guidance; selection is based on the site and severity of infection, immune status, allergies, pregnancy, and potential drug interactions. Genetics is only one factor in how you respond to antibiotics. Because cat-scratch disease often improves on its own, genetic testing is rarely necessary, but sharing any past medication reactions can help your clinician tailor antibiotics used for cat-scratch disease to you.
Interactions with other conditions
Cat-scratch disease can behave very differently if another health condition is in the mix. A condition may “exacerbate” (make worse) symptoms of another, and this is most clear in people with weakened immune systems from HIV, organ transplants, cancer treatment, or long-term steroids; in these settings, the infection can become more severe and spread beyond the lymph nodes to the skin, liver, spleen, or eyes. People with existing heart valve problems or artificial valves are also at higher risk for a serious complication called infective endocarditis, where the heart valves become infected and cause prolonged fever, fatigue, and weight loss. Swollen lymph nodes from cat-scratch disease can look similar to illnesses like lymphoma or tuberculosis, so doctors sometimes run extra tests to sort out the cause. Because exposure to cats can also bring other infections such as toxoplasmosis, overlapping fever and tender lymph nodes can make the picture confusing, and your clinician may check for more than one infection at once. If early symptoms of cat-scratch disease show up while you’re already being treated for another illness, tell your care team promptly so they can coordinate testing and antibiotics.
How genes can cause diseases
Humans have more than 20,000 genes, each carrying out one or a few specific functions in the body. One gene instructs the body to digest lactose from milk, another tells the body how to build strong bones and another prevents the body's cells from beginning to multiply uncontrollably and developing into cancer. As all of these genes combined are the building instructions for our body, a defect in one of these genes can have severe health consequences.
Through decades of genetic research, we know the genetic code of any healthy/functional human gene. We have also identified that in certain positions on a gene, some individuals may have a different genetic letter from the one you have. We call these hotspots "Genetic Variations" or "Variants" in short. In many cases, studies have been able to show that having the genetic letter "G" in the position makes you healthy, but having the letter "A" in the same position disrupts the gene function and causes a disease. Genopedia allows you to view these variants in genes and summarizes all that we know from scientific research, which genetic letters (Genotype) have good or bad consequences on your health or on your traits.
History
Throughout history, people have described sudden fevers and tender swellings after minor scrapes or animal scratches. In many households, it was a playful kitten’s nip followed by a sore spot under the arm a week later. Doctors noted the pattern long before they knew the cause: a small bump at the scratch site, then a swollen lymph node, usually near the scratch, and a short-lived fever.
First described in the medical literature as a cluster of swollen lymph nodes following cat scratches, the condition drew interest in the early 1900s. For decades, it was defined by symptoms and the clear link to cats, but not by a known germ. Skin tests and biopsy findings helped clinicians recognize cat-scratch disease more reliably, and case reports showed it was usually mild in children and teens, though adults could have it too.
As medical science evolved, researchers used improved microscopes and new lab techniques to hunt for the culprit. In the late 20th century, the bacterium Bartonella henselae was identified as the main cause, carried by fleas that live on cats. This discovery connected everyday events—kittens, flea bites, playful scratches—to a specific organism, and it explained why cat-scratch disease often shows up after contact with young cats.
Over time, descriptions became more complete. Most people with cat-scratch disease recover without lasting problems, but doctors also documented less common patterns: eye inflammation, nervous system symptoms, or widespread illness in people with weakened immune systems. These reports broadened the medical picture while confirming that the typical illness remains self-limited.
In recent decades, knowledge has built on a long tradition of observation. Blood tests and imaging improved diagnosis, and antibiotics were studied for more severe cases. Public health guidance emphasized simple prevention—flea control for pets and careful cleaning of scratches—reflecting what families had long noticed helped.
Understanding the history of cat-scratch disease shows how careful observation, then lab discovery, shaped today’s approach. What began as a recognizable story in clinics and homes is now a well-defined infection with a known cause, clear risk factors, and practical steps to reduce the chance of getting sick. Knowing the condition’s history also reassures many living with cat-scratch disease that the usual course is mild and temporary, even as medicine remains ready for the uncommon, more serious forms.