Latent Tuberculosis (TB) Infection

Latent TB is an infection in which TB germs stay alive in the body without making you sick. CDC pages from 2025 call it inactive TB, and it causes no symptoms and no illness. It usually shows a positive skin or blood test with a normal chest X-ray¹. LTBI is the medical abbreviation for latent TB infection⁷. The germs are present in small numbers, alive but inactive¹.

The difference from active TB disease decides what you need next. The comparison of latent vs active tuberculosis sets the two side by side.

No, latent TB is not contagious. CDC stated in 2025 that people with inactive TB cannot spread TB germs to others, so family and coworkers are safe. The germs spread from active TB disease of the lungs or throat, and usually not from kidney or spine TB⁴. Contacts of someone with inactive TB need no TB test, unlike contacts of someone with active TB disease¹. The page asking is tuberculosis contagious explains which forms spread.

You get latent TB by breathing in TB germs released into the air by someone with active TB disease. TB is not spread by shaking hands, sharing food or drink, kissing or touching toilet seats. TB germs can stay in the air for several hours⁴. Spread is more likely indoors or in poorly ventilated spaces such as a closed vehicle⁴. Frequent travel to countries where TB is common raises the risk of infection⁵. These include parts of Asia, Africa and Latin America⁵. So does living now or in the past in a homeless shelter, prison or jail⁵. Working in a hospital, shelter, correctional facility or nursing home raises it too⁵. The page asking whether does tuberculosis spread through touch covers everyday contact.

No, latent TB causes no symptoms, because the germs are not multiplying. People with latent TB feel well, and only a test shows the infection. A cough of 3 weeks or longer, fever or weight loss means active TB needs to be ruled out⁸. CDC guidance from 2025 tells people treated for latent TB to seek care if symptoms of TB disease appear². The list of TB symptoms in adults shows what to watch for.

Latent TB is found with a TB skin test or a TB blood test. A positive test followed by a normal chest X-ray and no symptoms points to latent TB. Testing is aimed at people at higher risk, such as close contacts and people born where TB is common⁹. People with weak immune systems are included⁹. A positive test shows TB infection, and further tests are needed to tell inactive TB from active disease⁹. Lab tests such as a sputum smear or culture, if done, come back negative in inactive TB¹. The tuberculosis (TB) test guide explains both tests.

Latent TB is treated with one or two TB medicines taken for 3 to 9 months. CDC guidance from 2025 prefers three short regimens of 3 or 4 months based on rifampin or rifapentine.

The 6- and 9-month isoniazid regimens are used when a short regimen is not an option². They carry more risk of side effects and lower completion than the short regimens². 3HP is recommended from age 2, but not during pregnancy². The Priftin label gives it under direct observation, while CDC guidance from 2025 requires that only for twice-weekly regimens². 4R suits people who cannot take isoniazid or were exposed to isoniazid-resistant TB². Medicine is taken on your own or by directly observed therapy³. Under it, a health worker watches each dose in person or virtually³. A missed dose is skipped, the next scheduled dose is taken, and the provider is told³. A provider checks in at least monthly for side effects and signs of active TB². The weekly regimen pairs isoniazid with rifapentine (Priftin).

Minor side effects of latent TB treatment include skin rash, upset stomach and nausea, and people usually keep taking the medicine. Signs of liver injury, such as stomach pain, vomiting or yellow skin or eyes, mean calling your provider right away. Rifampin and rifapentine turn urine, saliva, tears, sweat and breast milk orange, which is harmless³. They can permanently stain soft contact lenses³. Isoniazid can cause tingling or numbness in the hands or feet, and a provider may add vitamin B6 to prevent it³. Flu-like and allergic reactions are the most common side effect of 3HP. Drinking alcohol during treatment can harm the liver³. Rifampin and rifapentine may make some hormonal birth control less reliable, so CDC guidance from 2025 advises a barrier method². Liver blood tests at the start are not routine but are advised for some people². They include people with liver disease, regular alcohol use, HIV, or pregnancy or the first 3 months after birth². Report these other signs at once³.

• Dark urine
• Loss of appetite
• Dizziness
• Easy bruising or bleeding
• Blurred or changed vision
• Ongoing tiredness, fever or belly pain

Isoniazid has its own list of isoniazid liver and nerve side effects.

Yes, latent TB should be treated to prevent active TB disease, CDC advised in 2025, and the treatment is 90% effective. It is not recommended for everyone with a positive test. Active TB is ruled out first, and people with risk factors come first. People with no known risk factor may be offered treatment after a positive blood test². A skin test of 15 mm or more counts too². Pregnant people can usually wait until 2 to 3 months after birth unless their risk is high³. About 80% of TB cases in the US come from latent TB that was never treated⁷. Treatment is one of the main ways how to prevent tuberculosis works.

Yes, latent TB can become active TB disease when the immune system can no longer hold the germs in check. Without treatment, about 1 in 10 people with latent TB get sick with active TB. It can happen weeks after infection or years later⁴. Risk is highest with a weak immune system, diabetes, cancer or HIV⁴. Children under 5 and people infected within the last 2 years are at higher risk too⁵. So are people with an organ transplant, severe kidney disease, silicosis, low body weight or injection drug use⁵. The page on active tuberculosis disease covers what happens next.

No, latent TB itself causes no illness, and the danger lies in its turning into active TB disease. CDC guidance from 2025 says active TB disease spreads to others and can be deadly. Treatment for latent TB is much easier than treatment for TB disease, because fewer germs are present³.

No, TB germs can live in the body for years, and treatment is the best way to keep them from causing disease. A 2018 BMJ analysis argues that some people clear the germs, yet their skin or blood test can stay positive. The same analysis finds that most TB cases occur within 18 to 24 months of infection.

These short answers cover cure, numbers, work, testing and paperwork.