Many people with tuberculosis stay in the latent infection stage, but some develop the active disease. Both stages are treatable.

Tuberculosis (TB) is a bacterial infection that usually affects the lungs but can also attack other parts of the body. However, it can be fatal without correct treatment.

After the primary infection, most people enter an inactive infection stage where they experience no symptoms and cannot spread the disease. Others develop TB disease, or an active infection, which causes symptoms and can spread. Medication regimens can treat TB at both stages, although drug-resistant TB requires special approaches.

This article discusses the primary, latent, and active stages of TB and describes how the disease generally progresses.

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The bacterium Mycobacterium tuberculosis causes the TB infection.

Someone can contract TB when they breathe in the bacterium after a person with an active infection coughs, sneezes, sings, or speaks. However, according to the American Lung Association, TB does not spread easily.

The primary infection usually occurs in the middle part of the lungs. From there, the infection typically enters a latent, or inactive, stage but can sometimes quickly develop into active TB disease. Treatments are available for both stages.

Those with a higher risk of contracting a TB infection include anyone near someone with TB, such as:

  • people from regions or areas with high TB rates
  • people who work or live in hospitals, nursing homes, and other places that house people at high risk
  • friends and family of someone with a TB infection
  • people in groups with high TB transmission rates

A latent TB infection occurs when someone gets a TB infection, but their immune system makes it inactive and stops the bacterium from growing. People with a latent infection do not feel ill and cannot spread TB to others.

Many individuals with latent TB infection never develop TB disease, and the TB bacterium remains inactive for a lifetime. In others, especially those with weakened immune systems, the bacterium become active, multiply, and cause disease.

In this stage, blood or skin tests can indicate whether someone has TB.

While latent TB does not spread or cause symptoms, treatment is important for making sure it does not become active.

Treatment involves either 3–4 months or 6–9 months of one or more of the following medications:

  • Isoniazid
  • Rifampin
  • Rifapentine

Read more about latency TB.

An active TB infection, or TB disease, occurs when the TB bacterium grows and attacks the lungs or other parts of the body. This happens because the immune system cannot fight the bacterium effectively. TB disease causes symptoms and can spread to others.

For some people, an active TB infection can come from a latent infection that progresses. In other cases, TB disease can occur soon after exposure to the bacterium.

An active TB infection usually makes someone feel sick and can be fatal. Symptoms can include:

Treatment involves using one or multiple medications across several months. Some first-line medications include:

  • rifampin
  • pyrazinamide
  • ethambutol

In some cases, TB disease may be resistant to drugs or unresponsive to one or multiple medications. Treating drug-resistant TB disease can be complicated. It requires specialized approaches from a healthcare team, which take much longer to complete.

TB progresses differently for people. The primary infection usually becomes a latent TB infection first. In many cases, the latent infection never progresses, but for some people, TB may be latent for weeks, months, or years before becoming active.

An active TB infection occurs when someone’s immune system is not strong enough to fight the bacterium. Those at a higher risk of developing TB disease include anyone with weakened immune systems, including:

Tuberculosis is a disease that spreads when someone inhales the Mycobacterium tuberculosis bacterium from someone with an active infection.

The primary infection usually occurs in the center of the lungs. From there, the infection can enter a latent stage, or in fewer cases, become an active infection.

Latent TB causes no symptoms and cannot spread. Treatment involves a medication regimen. Some people will have a latent infection for weeks or years before it progresses into an active infection, but many will only stay in the latent stage.

An active TB infection, or TB disease, occurs when someone’s immune system cannot fight the bacterium effectively, and the bacterium attacks the body. TB disease can spread to others and can be fatal without treatment. Treatment involves a medication regimen over several months. In some cases, TB disease can be resistant to drugs and requires special treatment approaches.

TB can progress in different ways. While TB usually enters and stays in the latent infection stage, some people will eventually develop an active infection when their immune system weakens. Occasionally, some people develop an active TB infection right away.

Those with weakened immune systems face a higher risk of developing TB disease. This includes babies and young people, those with HIV, AIDS, or chronic conditions, people receiving chemotherapy or treatments for autoimmune disorders, and organ transplant recipients. Proper treatment can cure a TB infection.