Is Tuberculosis Contagious?

Yes, tuberculosis is contagious when a person has active TB disease in the lungs or throat. That person can spread TB germs into the air, and people nearby can breathe them in. People with inactive TB, and most people with TB outside the lungs, cannot spread it¹. Lung TB is the most common form. CDC data from 2025 show 70.9% of US cases in 2024 were in the lungs only⁴.

Knowing who can spread TB is the first step in preventing it. The guide on how to prevent tuberculosis covers testing, treatment and fresh air.

Tuberculosis is transmitted through the air, not by touch. When a person with active lung TB coughs, speaks or sings, TB germs enter the air and can stay for hours. Spread is more likely indoors, in a closed car and wherever air circulates poorly¹. CDC clinical guidance from 2025 says the germs travel in droplet nuclei 1 to 5 microns across⁵. These are small enough to float in room air⁵. A bout of coughing or 5 minutes of normal speech releases many more germs, and a sneeze releases the most⁶. That is why the answer to whether is tuberculosis airborne is yes.

TB usually spreads to people who spend a lot of time close to a sick person. People with active TB most often spread it to people they see every day, such as family, friends and coworkers. Short contact outdoors carries less risk than hours in a shared indoor room¹. Exposure that leads to infection usually lasts days, months or even years, and only rarely is a few minutes indoors enough⁶. CDC clinical guidance from 2025 says drug-resistant TB is no more infectious than drug-susceptible TB⁵. Spread from children under 10 is unusual, CDC guidelines from 2005 note⁷. In a San Francisco high school outbreak reported in March 2026, 227 of 1,359 students and staff tested positive. Of those, 207 had inactive TB. Anyone exposed to tuberculosis in a shared room should ask the health department about testing.

TB does not spread through touch or shared objects. You cannot catch TB by shaking hands, sharing food or drinks, touching bed linens or toilet seats, sharing a toothbrush, or kissing. These five contacts are safe¹.

• Shaking hands
• Sharing food or drinks
• Touching bed linens or toilet seats
• Sharing a toothbrush
• Kissing

The page on whether TB can spread through touch or surfaces explains why.

Only active TB of the lungs or throat is usually contagious. TB in other parts of the body, such as the kidney or spine, usually is not, and inactive TB never is. Inactive TB still needs attention, because about 1 in 10 people with it later develop active TB without treatment³. CDC clinical guidance from 2025 names the exceptions for TB outside the lungs⁵. They are lung disease at the same time, disease in the mouth or larynx, and an open, draining abscess⁵. CDC data from 2025 show 11.8% of US cases in 2024 had TB in the lungs and elsewhere at once⁴. Treating latent tuberculosis (TB) infection stops it from becoming the contagious kind.

TB stays contagious until treatment stops the spread, and after a few weeks of medicine most people may no longer be infectious. Your health care provider decides when you can go back to work or school, using follow-up sputum tests or X-rays. In hospital, isolation for confirmed lung TB ends after effective treatment, clinical improvement and 3 negative sputum smears on separate days⁸. The CDC infection control guideline from 2005 adds at least 2 weeks of standard multidrug treatment⁷. Canadian national standards from 2025 judge the end of infectiousness by clinical, X-ray or lab improvement, not by time alone⁶. In California, a local health officer may order home isolation for a person with infectious TB. That state law has applied since 1996. Feeling better is not the same as being cured, so every dose is still taken. Rules for tuberculosis isolation at home and in hospital follow these steps.

Someone exposed to TB is not contagious right away, but turns contagious once active disease develops, usually in the lungs or throat. Without treatment, about 5% of infected people develop TB disease within 2 years, and another 5% do so later in life. TB tests usually turn positive 2 to 12 weeks after infection, CDC guidelines from 2005 say⁷. Health departments tracing contacts assume the infectious period began 3 months before diagnosis, per the same 2005 CDC guidelines⁷. The longer a person has symptoms before diagnosis, the greater the risk of spread⁶. The page on how long until tuberculosis symptoms appear covers the timeline.

No, tuberculosis is not passed down in genes; it is caught from germs in the air. It often appears in several family members because people spread it to those they see every day. Genes can change how likely an infected person is to get sick. An early study of 205 twin pairs found both twins had TB in 65% of identical and 25% of non-identical pairs. Most inherited risk is spread across many common gene variants, and no genetic risk score is validated (Int J Mol Sci, 2025). The page asking is tuberculosis genetic looks at that research.

Yes, some people with active TB disease have no clear symptoms and can still spread it. People with inactive TB also have no symptoms, but they cannot spread TB to anyone. WHO wrote in 2026 that TB symptoms may be mild for many months⁹. That makes it easy to spread TB without knowing it⁹. Around half of active TB found worldwide is subclinical, meaning it causes no clear symptoms (Emery, 2023). The same 2023 modelling study estimated that 68% of global TB spread comes from subclinical TB. Its range was wide, from 27% to 92%. Only active tuberculosis (TB) disease spreads, with or without symptoms.

Yes, reactivated TB is contagious when the germs that slept in the body cause active disease in the lungs or throat. More than 80% of active TB in the United States comes from inactive TB that was never treated. TB that returns after treatment is either a relapse of the same germs or a reinfection with a new strain. Genotyping tells the two apart. In low-incidence settings, relapse made up about 83% of recurrences (Vega, 2021). The page asking can you get tuberculosis twice explains both routes.

A person with TB is more contagious with a frequent or severe cough, lung cavities or many germs in the sputum. Effective treatment quickly cuts the cough and the number of germs in the sputum. Lung cavities on a chest X-ray usually mean a person is more infectious, CDC guidelines from 2005 say⁷. That is most true with a positive sputum smear⁷. Higher sputum smear grades carry the highest risk of spread⁶. The same standards name smoking and overcrowding as factors that raise the risk of spread⁶. The page on tuberculosis cavitation explains how cavities form.

These short answers cover history, other forms of TB, and a few unusual routes.