Tuberculosis: Causes, Symptoms, Testing, and Treatment

About a quarter of the world’s population is estimated to carry tuberculosis bacteria, making it one of the most widespread infections on the planet. In the United States, where TB rates had declined for decades, the CDC has reported a renewed rise in recent years: provisional 2024 data showed more than 10,000 reported cases – the highest annual number in over a decade (since around 2013) – after an earlier increase in 2023. Globally, tuberculosis is again the leading cause of death from a single infectious agent; the World Health Organization estimates roughly 10.7 million people fell ill with TB and about 1.25 million died from it in 2024. Understanding how TB spreads, the critical difference between latent and active disease, and why completing treatment is non-negotiable can protect both individual and public health. For context on infectious and chronic conditions, see our medical conditions guide.

What Is Tuberculosis?

Tuberculosis is caused by Mycobacterium tuberculosis, a slow-growing bacterium that primarily targets the lungs but can affect virtually any organ – including the kidneys, spine, brain, and lymph nodes. TB spreads through the air when a person with active pulmonary tuberculosis coughs, sneezes, speaks, or sings, releasing tiny droplet nuclei that can remain suspended in the air for hours.

What makes TB unusual among infections is its ability to exist in two distinct states within the body. In latent TB infection (sometimes now called simply TB infection), the immune system contains the bacteria and prevents active disease. The person is infected but not sick and cannot spread TB to others. In active TB disease, the bacteria overcome immune defenses, multiply, and cause symptoms. Only active TB of the lungs or larynx is contagious.

According to the World Health Organization, roughly 5 to 10 percent of people with latent infection will develop active TB at some point in their lives, with the highest risk in the first two years after infection. Certain conditions dramatically increase this progression risk – HIV co-infection, for example, raises it to several percent per year rather than per lifetime, and other forms of immune suppression (such as TNF-inhibitor drugs, organ transplantation, or dialysis) also raise the risk.

How Tuberculosis Spreads

TB transmission generally requires prolonged, close contact with someone who has active pulmonary or laryngeal tuberculosis. Brief, casual encounters – passing someone in a grocery store, for example – rarely result in transmission. The CDC identifies household members, close friends and coworkers, and people who share enclosed, poorly ventilated spaces as those at greatest risk of exposure.

Several environmental factors influence transmission. Poorly ventilated, crowded indoor settings – including correctional facilities, homeless shelters, nursing homes, and dormitories – facilitate spread. TB bacteria are inactivated by ultraviolet light, so outdoor transmission is extremely rare. The infectiousness of a person with active TB depends on the bacterial burden in their sputum, the frequency and force of their cough, and the duration of contact before treatment begins.

TB cannot be spread by shaking hands, sharing food or drinks, touching surfaces, or kissing. It is not transmitted by blood or through sexual contact. Once a person with active TB has been on effective therapy for a few weeks and is showing clinical improvement (and, ideally, has converted their sputum smears to negative), they are generally considered much less infectious, though the exact timeline is determined case by case with public-health guidance.

Latent TB Infection vs. Active TB Disease

Distinguishing latent TB infection from active TB disease is fundamental to TB management. A person with latent TB has no symptoms, a normal chest X-ray, and negative sputum studies. They feel completely healthy and pose no transmission risk. Their only evidence of infection is a positive TB skin test or blood test showing immune sensitization to M. tuberculosis.

Active TB disease produces symptoms that depend on the site of infection. Pulmonary TB – the most common form – causes a persistent cough lasting three weeks or longer, sputum that is sometimes blood-tinged, chest pain, unintentional weight loss, loss of appetite, fever, night sweats, and fatigue. According to the National Heart, Lung, and Blood Institute, extrapulmonary TB can cause symptoms specific to the affected organ: back pain and stiffness with spinal TB, headache and altered consciousness with TB meningitis, or painless lymph-node swelling with lymph-node TB.

The distinction matters enormously for treatment. Latent TB is treated with shorter, simpler regimens to prevent progression to active disease. Active TB requires a longer, multi-drug regimen to cure the infection and prevent drug resistance. Treating latent TB is a critical public-health strategy – shrinking the reservoir of latently infected individuals who might later develop active disease reduces future transmission, which is central to U.S. TB elimination efforts.

Testing for Tuberculosis

Two types of tests detect TB infection: the tuberculin skin test (TST, also called the Mantoux test or PPD) and interferon-gamma release assays (IGRAs). Neither test alone can distinguish latent infection from active disease – additional evaluation is needed for that determination.

The TST involves injecting a small amount of purified protein derivative (PPD) under the skin of the forearm and reading the result 48 to 72 hours later. A raised, hardened area (induration) at the injection site is measured in millimeters. The threshold for a positive result varies by risk: 5 mm or more for the highest-risk groups (HIV-positive, recent TB contacts, people who are significantly immunosuppressed), 10 mm or more for moderate-risk groups (health-care workers, people from high-prevalence countries, residents of congregate settings), and 15 mm or more for people with no known risk factors.

IGRAs – such as the QuantiFERON-TB Gold Plus and T-SPOT.TB tests – are blood tests that measure the immune system’s response to TB-specific antigens. According to the CDC, IGRAs offer several advantages: they require only a single visit, are not affected by prior BCG vaccination (which can cause false-positive skin tests), and have higher specificity. They are the preferred test for people who have received BCG vaccine, those unlikely to return for a skin-test reading, and many routine adult screening scenarios in the United States.

When TB infection is detected, a chest X-ray is the next step to evaluate for active pulmonary disease. If the chest X-ray is abnormal or the patient is symptomatic, sputum samples are collected for acid-fast bacilli (AFB) smear and culture. Sputum culture remains the gold standard for confirming active TB and testing for drug susceptibility. Molecular (nucleic acid amplification) tests, such as the GeneXpert MTB/RIF assay, can detect M. tuberculosis DNA and rifampin resistance within hours, allowing faster diagnosis and appropriate isolation.

Treatment of Latent TB Infection

Treating latent TB prevents the roughly 5 to 10 percent lifetime risk of progression to active disease. The CDC and the National Tuberculosis Coalition of America now prefer shorter, rifamycin-based regimens: three months of once-weekly isoniazid plus rifapentine (the “3HP” regimen), four months of daily rifampin (4R), or three months of daily isoniazid plus rifampin (3HR). These have largely replaced the older nine-month daily isoniazid course because they have better completion rates and comparable effectiveness.

The 3HP regimen is notable for its convenience – only 12 doses taken once weekly, which may be given as self-administered therapy or through directly observed therapy (DOT), where a health-care worker confirms each dose. Completion rates for these short-course regimens are substantially higher than for the traditional nine-month isoniazid course, and higher completion means better protection.

Side effects of latent-TB treatment are generally manageable but must be monitored by a clinician. Isoniazid can cause liver inflammation (hepatotoxicity) and peripheral neuropathy (usually prevented by supplementing with vitamin B6). Rifampin and rifapentine can cause harmless orange discoloration of urine and other body fluids, important drug interactions (particularly with oral contraceptives, warfarin, and HIV medications), and, rarely, flu-like hypersensitivity reactions. Because specific drugs, doses, and monitoring depend on your health, age, and other medications, a latent-TB regimen must be prescribed and supervised by a clinician – it should never be self-directed.

Treatment of Active TB Disease

Active TB treatment follows a standardized protocol designed to cure the infection and prevent drug resistance. The long-standing regimen for drug-susceptible pulmonary TB has an intensive phase and a continuation phase. The intensive phase includes four drugs – isoniazid, rifampin, pyrazinamide, and ethambutol (collectively “RIPE” therapy) – followed by a continuation phase of isoniazid and rifampin, for a total of about six months in uncomplicated cases. For some patients, a newer four-month regimen using rifapentine and moxifloxacin is now an option. Treatment always involves several drugs taken together for months; there is no safe short cut, and no one should attempt to self-treat or set their own doses.

According to the American Thoracic Society, treatment must be completed in its entirety – stopping early or missing doses is the primary driver of treatment failure and drug-resistant TB. Directly observed therapy (DOT), in which a health-care worker watches the patient swallow every dose, is a standard of care in the United States and is critical for ensuring adherence. Video DOT (vDOT), where patients record themselves taking medication on a smartphone, is now widely accepted as an alternative.

Extrapulmonary TB may require longer treatment – TB meningitis, for example, is typically treated for 9 to 12 months, with corticosteroids added for TB meningitis and TB pericarditis to reduce inflammation-related complications. Drug-resistant TB – including multidrug-resistant TB (MDR-TB, resistant to at least isoniazid and rifampin) and extensively drug-resistant TB (XDR-TB) – requires specialized treatment with second-line drugs for many months. These regimens are more complex, more toxic, and historically less effective than standard therapy, which is exactly why completing first-line treatment correctly is so important.

Drug-Resistant Tuberculosis

Drug-resistant TB emerges when bacteria mutate and survive exposure to anti-TB medications – primarily because of incomplete treatment, incorrect prescribing, poor drug quality, or missed doses. The WHO’s Global Tuberculosis Report estimates roughly 400,000 new cases of multidrug-resistant or rifampin-resistant TB occur worldwide each year, of which only a fraction are diagnosed and successfully treated.

In the United States, MDR-TB is relatively uncommon – on the order of 100 cases per year – but it requires referral to specialized treatment centers. Care for drug-resistant TB has advanced significantly: the WHO now recommends a mostly oral, six-month BPaLM regimen (bedaquiline, pretomanid, linezolid, and moxifloxacin) for many people with MDR/rifampin-resistant TB, based on trials such as TB-PRACTECAL that showed high cure rates. This is a major improvement over the older, longer, injection-based regimens that could last a year and a half or more.

Preventing drug resistance depends on treating every TB case with the correct regimen for the correct duration under appropriate supervision. This is a public-health imperative, not just an individual treatment concern. Understanding the economic burden of drug-resistant infections reinforces why adherence and proper treatment protocols matter so much.

Prevention Strategies

The BCG (Bacille Calmette-Guerin) vaccine is widely used in countries with high TB burden and is part of routine childhood immunization in many of them. However, BCG is not routinely recommended in the United States because of the relatively low risk of exposure here, the vaccine’s variable effectiveness against adult pulmonary TB, and its interference with skin-test interpretation. BCG is most valuable for preventing severe forms of childhood TB, including TB meningitis.

In the United States, TB prevention relies on targeted testing and treatment of latent TB infection in higher-risk populations, rapid identification and treatment of active cases, contact investigation (identifying and testing people exposed to a known case), infection-control measures in health-care and congregate settings, and screening of people arriving from high-prevalence countries.

Health-care workers, people born in or who frequently travel to TB-endemic countries, residents and employees of congregate settings, people with HIV or other immune-compromising conditions, and close contacts of someone with active TB should be prioritized for testing. Environmental controls – adequate ventilation, HEPA filtration, and ultraviolet germicidal irradiation – reduce airborne transmission risk in health-care and institutional settings.

Frequently Asked Questions

Can tuberculosis be cured?

Yes. Drug-susceptible TB is curable with a standard multi-drug regimen, and success rates are high when treatment is completed properly. Even drug-resistant TB can now be cured in most cases with newer regimens such as BPaLM, though treatment is longer and more complex. The critical factor is completing the entire course – stopping early risks treatment failure, relapse, and the development of drug resistance.

How do I know if I have latent TB?

Latent TB has no symptoms. The only way to know is through testing – either a tuberculin skin test (TST) or an interferon-gamma release assay (IGRA) blood test. If you are in a higher-risk group – born in a TB-endemic country, had close contact with someone with active TB, are living with HIV, are a health-care worker, or live or work in a congregate setting – you should be tested. A positive test followed by a normal chest X-ray and no symptoms indicates latent infection, which can be treated to prevent future disease.

Is TB still a problem in the United States?

Yes. While U.S. TB incidence is far lower than in many other countries, TB has not been eliminated – and the numbers have been moving in the wrong direction. Provisional 2024 data showed more than 10,000 reported cases, the highest number in over a decade, and millions of Americans are estimated to have latent TB infection. TB disproportionately affects people born outside the U.S., some racial and ethnic minority groups, people experiencing homelessness, and people with HIV. Public-health experts attribute part of the recent rise to catch-up after pandemic-era disruptions in screening and to global travel and migration patterns.

What happens if I stop taking TB medication early?

Stopping TB treatment early is dangerous for both you and the public. The bacteria that survive partial treatment may be the ones with natural resistance to the drugs used, leading to drug-resistant TB. That means your TB could relapse with bacteria that are harder, longer, and more expensive to treat. You also risk remaining infectious or becoming infectious again, potentially spreading resistant TB to others. Always complete your full course of treatment, even after you feel better, and talk to your care team about any side effects rather than stopping on your own.

Can I be around my family if I have active TB?

During the initial weeks of treatment, precautions are necessary – especially around household members who are young children, elderly, or immunocompromised. You should stay home, cover your mouth and nose when coughing, ventilate your living space, and wear a mask around others as advised. After a few weeks of effective treatment with documented clinical improvement and, ideally, negative sputum smears, your doctor and the health department can assess whether you are no longer infectious. Close contacts should be tested for TB infection regardless.

What to Do If You’re Concerned About TB

If you believe you may have been exposed to tuberculosis – through contact with a known case, travel to a high-burden country, or work in a high-risk setting – get tested. Testing is widely available through primary-care physicians, local health departments, and community health centers, and many health departments offer free or low-cost TB testing and treatment.

If you have been diagnosed with latent TB, take treatment seriously. The newer short-course regimens are far more manageable than the old nine-month protocols, and completing one essentially eliminates your future risk of developing active disease – one of the most effective preventive health measures available.

If you have been diagnosed with active TB, follow your treatment plan meticulously. Work with your health department, participate in DOT or vDOT as recommended, report side effects promptly so they can be managed, and complete every dose. TB treatment is one of the genuine success stories of modern medicine – but only when the full course is finished. Your cooperation protects your own health and the health of everyone around you.

Sources

• Centers for Disease Control and Prevention (CDC) – Tuberculosis (TB): About, Testing and Diagnosis, Treatment, and U.S. surveillance data (provisional 2024 figures)
• World Health Organization (WHO) – Tuberculosis fact sheet and Global Tuberculosis Report (2024/2025 estimates)
• National Heart, Lung, and Blood Institute (NHLBI) – Tuberculosis
• American Thoracic Society / CDC / IDSA – Treatment of Drug-Susceptible and Drug-Resistant Tuberculosis clinical guidelines
• MedlinePlus (U.S. National Library of Medicine) – Tuberculosis