Latent tuberculosis infection
What is Latent tuberculosis infection?
Latent tuberculosis infection, or LTBI, means you carry tuberculosis bacteria in your body but they are dormant. The bacteria are alive but not active. Your immune system keeps them under control.
People with latent TB feel completely healthy and have no symptoms. They cannot spread the bacteria to others. This makes LTBI very different from active TB disease, where bacteria multiply and cause illness.
About one quarter of the world's population has latent TB infection. Most people with LTBI will never develop active TB disease. However, the bacteria can wake up later in life if your immune system becomes weak. This is why testing and treatment matter, especially for people at higher risk.
Symptoms
Most people with latent tuberculosis infection have no symptoms at all. This is what makes it latent, or hidden.
- No cough or breathing problems
- No fever or night sweats
- No weight loss or fatigue
- Normal chest X-ray results
- No signs of illness or infection
You feel completely normal with LTBI. Symptoms only appear if the infection progresses to active TB disease. At that point, bacteria become active and begin causing damage to the lungs or other organs.
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Causes and risk factors
Latent TB infection happens when you breathe in tuberculosis bacteria from someone with active TB disease. The bacteria enter your lungs when an infected person coughs, sneezes, speaks, or sings. Your immune system then walls off the bacteria, keeping them dormant instead of letting them multiply.
Risk factors include close contact with someone who has active TB, living in or traveling to countries where TB is common, working in healthcare settings, living in crowded conditions, and having a weakened immune system. People who recently moved from high-TB countries, those with HIV, diabetes, or kidney disease, and individuals taking immune-suppressing medications face higher risk of progression to active disease. Age matters too, as young children and older adults are more vulnerable.
How it's diagnosed
Latent TB infection is diagnosed through blood tests or skin tests. The QuantiFERON-TB Gold Plus blood test measures your immune response to TB bacteria. A positive result means you have been exposed to TB and likely have a latent infection. This test requires only one visit and is not affected by prior TB vaccination.
The tuberculin skin test, or TST, is another option where a small amount of testing fluid is injected under the skin. You return in 48 to 72 hours for a reading. After a positive blood or skin test, your doctor will order a chest X-ray to rule out active TB disease. Talk to a healthcare provider about specialized TB testing to determine if you have been exposed to tuberculosis bacteria.
Treatment options
- Preventive antibiotic therapy to kill dormant bacteria and prevent active disease
- Isoniazid taken daily for six to nine months
- Rifampin taken daily for four months
- Combination therapy with isoniazid and rifapentine taken weekly for three months
- Regular monitoring by a healthcare provider during treatment
- Avoiding alcohol to protect your liver while on medication
- Eating a balanced diet rich in protein, fruits, and vegetables
- Getting enough sleep to support immune function
- Managing underlying conditions like diabetes or HIV
Frequently asked questions
Latent TB means you carry dormant bacteria that cause no symptoms and cannot spread to others. Active TB disease means bacteria are multiplying, making you sick with symptoms like cough and fever. People with active TB can spread the infection to others through the air.
Yes, but it only happens in about 5 to 10 percent of people with latent TB. Most cases of progression occur within the first two years after infection. People with weakened immune systems face much higher risk of the bacteria waking up and becoming active.
Two main tests detect latent TB. The QuantiFERON-TB Gold Plus blood test measures immune response to TB bacteria with one visit. The tuberculin skin test requires an injection and a return visit 48 to 72 hours later to check for a reaction.
Testing is recommended for people who have been in close contact with someone with active TB. Those who live in or travel to countries with high TB rates should also get tested. Healthcare workers, people with HIV or diabetes, and anyone taking immune-suppressing medications benefit from screening.
Treatment is often recommended even without symptoms because it prevents progression to active disease. People at high risk of progression, like those with HIV or recent infection, should definitely consider treatment. Your doctor will weigh your risk factors to help you decide.
Treatment length depends on the medication regimen your doctor prescribes. Common options include daily isoniazid for six to nine months or daily rifampin for four months. A shorter option combines isoniazid and rifapentine taken weekly for just three months.
No, you cannot spread latent TB infection to anyone. The bacteria are dormant and not multiplying in your body. Only people with active TB disease can spread the infection through coughing, sneezing, or talking.
Most people with untreated latent TB never develop active disease. However, 5 to 10 percent will progress to active TB at some point in their lives. The risk increases significantly if your immune system becomes weakened by illness, age, or medication.
Some people experience mild side effects like upset stomach or loss of appetite. Rarely, TB medications can affect liver function, so your doctor will monitor you during treatment. Avoiding alcohol helps protect your liver while taking these medications.
It is possible to get re-infected if exposed to TB bacteria again after treatment. This is more common in areas where TB is widespread. However, completing treatment significantly reduces your risk of developing active TB disease even if you are exposed again.