The Evidence on Tuberculosis Basics, Without the Hype

Key takeaways

• How it spreads: through the air when someone with TB disease of the lungs or throat coughs, speaks or sings
• Latent TB infection: no symptoms and not contagious, but can become TB disease later
• Most useful single change: Ask your doctor about TB testing if you were born in or lived in a country where TB is common, live or work in a shelter or correctional facility, or have been near someone with TB disease.
• Commonest mistake: Stopping treatment early, which can lead to drug-resistant TB.
• See a doctor if any of the signs under "When to speak to a doctor" below apply to you.

What it is

A bacterial infection that usually affects the lungs and can stay inactive in the body (latent TB infection) or cause illness (TB disease). It sits within Infectious Diseases. What follows are the published numbers, not the ones that get passed around.

The numbers, in one place

What helps

What follows is the practical part: the things guidance actually asks of you.

• Ask your doctor about TB testing if you were born in or lived in a country where TB is common, live or work in a shelter or correctional facility, or have been near someone with TB disease
• Tell your doctor if you have HIV, diabetes, or take medicines that weaken the immune system, since these raise the risk of TB disease
• Take every dose of TB treatment; ask about directly observed therapy or video check-ins if that helps
• Follow your health department's advice about staying home while contagious

What to avoid

What to steer clear of, and why it catches people out.

• Stopping treatment early, which can lead to drug-resistant TB
• Assuming a positive test always means you can spread TB; latent infection is not contagious
• Ignoring a long-lasting cough because it is not painful

In depth

Tuberculosis is caused by Mycobacterium tuberculosis, a slow-growing bacterium with a thick, waxy outer coat that helps it survive inside the body. When someone breathes in TB bacteria, immune cells surround them in the lungs and wall them off in small clusters. The bacteria can stay alive but inactive inside these clusters for years. This is latent TB infection: the person feels well, has a normal chest X-ray in most cases, and cannot spread TB.

If the immune system can no longer keep the bacteria contained, they begin to multiply and cause TB disease. The risk is highest in the first couple of years after infection and whenever the immune system is weakened, for example by HIV, diabetes, some cancer treatments or medicines that suppress the immune system. TB disease most often affects the lungs but can involve the lymph nodes, spine, kidneys, brain and other organs.

TB is curable, but treatment takes months because the bacteria divide slowly and some can lie dormant inside tissues where drugs reach less easily. Using several drugs together and completing the full course kills the bacteria and prevents drug resistance. Public health departments play a central role in TB care in the US, providing testing, treatment support and contact tracing, often at no cost to the patient.

Signs and symptoms

• A cough lasting 3 weeks or longer, which may bring up mucus
• Coughing up blood or blood-streaked mucus
• Chest pain, especially when breathing or coughing
• Fever, chills and drenching night sweats
• Weight loss and loss of appetite
• Ongoing weakness or tiredness
• Symptoms depending on the organ affected, such as back pain or swollen glands in the neck

Causes and risk factors

• Close, prolonged contact with someone who has TB disease of the lungs or throat
• Being born in or having lived in a country where TB is common
• Living or working in shelters, correctional facilities or long-term care facilities
• HIV infection, which greatly raises the chance of latent TB becoming active
• Diabetes, kidney failure, silicosis, heavy alcohol use, smoking or drug use
• Medicines that weaken the immune system, including some used for rheumatoid arthritis and after organ transplants

How it is checked

Testing for TB infection uses either a blood test called an interferon-gamma release assay (IGRA) or a TB skin test, which is read 2 to 3 days after a small injection under the skin. Neither test can tell latent infection from TB disease. A positive result leads to a symptom review, an exam and a chest X-ray to look for signs of active disease.

If TB disease is suspected, you will usually be asked to cough up sputum samples, often on several days. These are examined under a microscope, tested with rapid molecular methods that can also detect some drug resistance, and grown in culture, which can take several weeks but gives the most complete information about which drugs will work. Other samples or scans may be needed for TB outside the lungs.

Treatment and support options

Treating latent TB infection

Treating latent infection greatly lowers the chance of developing TB disease later. CDC prefers shorter regimens based on rifamycin drugs, such as 3 months of a once-weekly combination or 3 to 4 months of daily pills, when they suit you. Longer regimens are used when needed. Your doctor will check for drug interactions, including with hormonal birth control and HIV medicines.

Treating TB disease

TB disease is treated with a combination of several drugs, usually for at least 4 to 6 months and sometimes longer, depending on the regimen and how the infection responds. Most people stop being contagious within weeks of starting effective treatment, but continuing to the end is what prevents the infection from coming back.

Directly observed therapy

Health departments often offer directly observed therapy, in which a health worker watches you take each dose, either in person or by video on a phone. It can feel intrusive at first, but many people find it makes it easier to stay on track, and it gives a regular chance to report side effects and get support.

Drug-resistant TB

Some TB strains are resistant to one or more of the main drugs. Drug-resistant TB needs different combinations, chosen based on lab testing, and is managed by TB specialists working with the health department. Treatment has improved in recent years, with newer all-oral regimens that are shorter than older approaches.

Prevention

• Get tested if you have risk factors, as USPSTF recommends for adults at increased risk
• Complete treatment for latent TB infection if it is found
• Get tested promptly if you have been in close contact with someone with TB disease
• Improve ventilation and natural light in shared living spaces
• Ask about TB testing before starting medicines that weaken the immune system

Day to day

Months of treatment take commitment. Pill organizers, phone reminders and taking doses at the same time every day all help. Report side effects early rather than skipping doses: nausea, loss of appetite, yellowing skin or eyes, dark urine, numbness or tingling, rash or changes in vision can all be signs your doctor needs to adjust treatment. Some TB drugs turn urine, sweat and tears orange, which is harmless.

If you have TB disease of the lungs, you may need to stay home from work, school and public places until your health department says you are no longer contagious, usually after some weeks of effective treatment and improving test results. Health workers will also talk with you about close contacts who should be tested. Your information is kept confidential, and many health departments can help with practical needs during this time.

For specific groups

People with HIV

HIV is one of the strongest risk factors for latent TB turning into TB disease. Everyone with HIV should be tested for TB infection, and TB and HIV treatment are coordinated carefully because several drugs interact.

Young children

Children under 5 are more likely to develop TB disease quickly after infection and to develop severe forms such as TB meningitis. Children exposed to someone with TB disease need prompt testing and may be started on medicine even before results are final.

Pregnancy

TB disease can and should be treated during pregnancy, because untreated TB poses a greater risk to both parent and baby than standard treatment. Decisions about treating latent infection during pregnancy depend on individual risk and are made with your provider.

People born outside the US

Most TB cases in the US now occur in people born in countries where TB is common, often from an infection picked up years earlier. Testing and treating latent infection is one of the most effective ways to prevent future illness.

Questions to ask your doctor

• Based on my history, should I be tested for TB infection?
• Does my positive test mean latent infection or TB disease?
• Which treatment regimen is best for me, and how long will it last?
• Do my other medicines, including birth control, interact with TB drugs?
• What side effects should make me call you right away?
• When will I no longer be contagious?

More questions, answered

Can I spread latent TB infection?

No. People with latent TB infection have no symptoms and cannot pass TB to others. Only people with TB disease of the lungs or throat can spread it, and they usually stop being contagious within weeks of starting effective treatment.

Why should I treat latent TB if I feel fine?

Latent infection can become TB disease months or years later, especially if your immune system weakens. Treating it now is shorter and simpler than treating TB disease later, and it protects the people around you as well.

Will the BCG vaccine affect my TB test?

BCG, a TB vaccine given in many countries, can cause a positive TB skin test. The TB blood test is not affected by BCG, so it is usually the preferred test for people who received it. A positive blood test should not be dismissed as a BCG effect.

Is TB still a problem in the US?

TB is much less common in the US than in many other countries, but cases are reported in every state each year, and most come from latent infections that become active. Testing and treating people at higher risk is a key part of prevention.

Can I drink alcohol during treatment?

Several TB medicines can strain the liver, and alcohol adds to that risk. Your doctor will usually advise avoiding or limiting alcohol during treatment and may check your liver with blood tests.

What happens if I miss doses or stop early?

Missing doses gives surviving bacteria a chance to grow back and become resistant to the drugs, making TB harder and longer to treat. If you miss doses, tell your care team right away rather than doubling up; they will tell you how to continue.

Related topics

• The Evidence on Antibiotics, Without the Hype (Immunity)
• Persistent Cough: What the Evidence Actually Says (Respiratory Health)
• Shingles Vaccination: What the Evidence Actually Says (Vaccinations)
• Hepatitis B and C: What the Evidence Actually Says (Liver Health)

Where to go next

• Tuberculosis Basics: The Practical To-Do List
• What People Get Wrong About Tuberculosis Basics
• Tuberculosis Basics — the reference entry
• Infectious Diseases: The Complete Guide
• RSV (Respiratory Syncytial Virus): Sorting the Evidence From the Noise
• COVID-19: What the Evidence Actually Says

When to speak to a doctor

See your doctor for a cough lasting 3 weeks or more, coughing up blood, chest pain, night sweats, fever or unexplained weight loss. Call 911 for coughing up large amounts of blood or severe trouble breathing.

Where this comes from

• CDC — About Tuberculosis
• US Preventive Services Task Force — Latent Tuberculosis Infection in Adults: Screening

How this page was put together

Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarized or generalized beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.

Medical disclaimer

This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.