Latent Tuberculosis Infection vs. Active TB Disease: What’s the Difference?

Tuberculosis (TB) is unlike most bacterial infections in that it usually doesn’t cause symptoms immediately. Even when it starts to make you sick, symptoms come on very gradually and can often be confused with other conditions.

Most commonly, tuberculosis goes through three stages:

• Primary TB infection
• Latent TB infection
• Active TB disease

Millions of people carry latent TB bacteria but never develop active tuberculosis. In fact, it’s estimated that as many as 13 million people in the United States have a latent TB infection. (1,2,3)

About 30 percent of people who get exposed to Mycobacterium tuberculosis will develop latent TB, and if that’s left untreated, around 5 to 10 percent of those people could end up getting active tuberculosis disease at some point in their lifetime. The number is much higher for people infected with HIV. (3,4)

Tuberculosis is more likely to enter the active phase in people who have acquired the infection recently (in the past two years). It’s also more likely to be active among those whose immune systems are weakened.

In some literature, latent tuberculosis may also be referred to as “tuberculosis infection,” while active tuberculosis is also known as “tuberculosis disease,” as noted in a 2021 journal article.

Primary or Initial Tuberculosis Infection

Infection with M. tuberculosis begins when a person breathes in airborne bacteria.

This is more likely to happen if a person is in close contact with one or more people infected with active TB who are coughing or sneezing.

In many people, any inhaled bacteria are killed immediately by the immune system. In others, the TB bacteria are surrounded by macrophages, a type of white blood cell, and enter a dormant state. This is called latent infection, and this stage can last for years or even for life. But in certain populations, including infants, the elderly, those with recently acquired TB infection, and people with weakened immune systems, symptoms of active tuberculosis may start within weeks of primary infection. (2)

What It Means to Have a Latent TB Infection

While a person with latent TB has no symptoms and is not infectious, a tuberculin skin test or blood test for TB — called the interferon-gamma release assay, or IGRA — will be positive, showing that the person has not only been exposed to tuberculosis but has a latent (or “occult”) infection with the bacteria that causes tuberculosis. (2,5)

“You have a ticking bomb waiting for your immune system to get weak,” says Hayan Yacoub, MD, internal medicine practitioner at Austin Regional Clinic in Texas. Latent TB can also complicate treatment for potential health issues that happen later in life, he says. That’s why it’s important to identify and treat latent TB.

If a latent infection is discovered, treatment is recommended in certain individuals at high risk to prevent that person from developing active disease and to prevent the further spread of tuberculosis.

People at high risk of TB infection (such as those who work in hospitals) may be screened, sometimes annually, for latent infection.

Who Should Get Tested for Latent Tuberculosis?

In the United States, there isn’t a need to test everyone for latent TB because it’s unlikely most people will come in contact with someone who has the active disease.

“The average person doesn’t get exposed to TB,” says Lee Reichman, MD, MPH, the founding executive director at the Rutgers Global Tuberculosis Institute in Newark, New Jersey. “For example, if you work in publishing and just go to work and go home, we don’t test you because [exposure] is unlikely.”

Screening for latent TB is done based on your risk factors. The following populations should generally be screened: (6,7)

• People who have recently come to the United States from a country with a high rate of tuberculosis
• People whose work or living arrangement puts them in contact with people who have active tuberculosis
• People who struggle with injected drug use
• Children under age 4 or children and adolescents exposed to adults in high-risk categories
• People with other diseases that increase the risk of developing active TB once infected, such as insulin-requiring diabetes, end-stage renal disease, prior gastrectomy, or HIV infection
• People who are taking drugs that block tumor necrosis factor alpha (TNF-alpha), such as infliximab (Remicade), adalimumab (Humira), or etanercept (Enbrel), as well as those taking steroid medications at higher doses or over a longer period of time

People who plan to start chemotherapy for cancer or an immunosuppressive drug — to treat an autoimmune condition, for example — should also be screened for latent tuberculosis.

The risk of a latent TB infection becoming active is much higher in people infected with HIV than those without HIV. (8)

What Does Treatment for Latent TB Involve?

Treatment for latent TB involves less medication and a shorter regimen than treatment of active TB, says Alexea M. Gaffney-Adams, MD, an internist with subspecialty training in infectious disease at Stony Brook Medicine in Stony Brook, New York.

The CDC and the National Tuberculosis Controllers Association (NTCA) now recommend a short-course of a rifamycin (Aemcolo)-based three- or four-month latent TB infection treatment. The previous recommendation was a six- or nine-month isoniazid (Nydrazid) single-drug therapy. Some of the regimens your infectious disease doctor may recommend are:

• Three months of once-weekly isoniazid plus rifapentine (Priftin), called 3HP
• Four months of daily rifampin (Rifadin), called 4R
• Three months of daily isoniazid plus rifampin, called 3HR (5,9)

What It Means to Have Active Tuberculosis Disease

In active tuberculosis, the bacteria multiply in the body, causing noticeable symptoms. This is also when the disease can spread to others. The difference between active and latent TB is the amount of organisms in the body, according to Dr. Reichman.

The most common kind of tuberculosis, pulmonary tuberculosis, typically causes the following symptoms: (5,10)

• Breathing difficulty
• Chest pain
• Coughing, sometimes with phlegm
• Fatigue
• Fever
• Night sweats
• Weakness
• Weight loss
• Wheezing

In addition to the lungs, tuberculosis can affect other parts of the body, including the lymph nodes, other internal organs, bones and joints, or the brain. This form of the disease, called extrapulmonary tuberculosis, also causes fatigue, fever, night sweats, weakness, and weight loss, and it may also cause other symptoms depending on what body parts are affected.

Active TB is curable, but the disease can be deadly if left untreated. About 45 percent of people not infected with HIV, and almost all HIV-positive people, will die from TB without proper treatment. (11)

Tuberculosis is spread through the air, which means you can only get it by breathing contaminated air. If someone who is actively sick talks, coughs, sneezes, or speaks, they can spread TB. People with active TB can infect 10 to 15 other people they come into regular close contact with in the course of a year. (11)

The reality is that if someone does have active TB, they’re breathing bacteria out into the air, and anyone can pick them up, says Dr. Gaffney-Adams. “You’re most likely to spread it to your household, but it can definitely spread elsewhere.”

Who Should Get Tested for Active TB Disease?

If you find out you’ve been exposed to someone with TB, you need to be screened, says Gaffney-Adams. If a first screening was negative, she recommends going in for testing again, especially if you experience any respiratory symptoms.

Screening is recommended for anyone with the following symptoms of active TB: (7)

• Coughing that lasts for three weeks or longer
• Weight loss that can’t be explained
• Coughing up blood
• Chest pain
• Loss of appetite
• Night sweats
• Fever
• Fatigue

According to Gaffney-Adams, who has treated several cases of both latent and active TB, night sweats is a very common symptom in active TB disease. It’s usually pretty dramatic, she says, like sweating so heavily that a person needs to get up and change sheets and clothes.

What Does Treatment for Active TB Involve?

The treatment for any type of active tuberculosis is long-term administration of antibiotics.

Because there are so many drug-resistant strains of TB, people with active disease must take more than one antibiotic to ensure that all of the bacteria are killed. In addition, because tuberculosis bacteria grow slowly, it’s necessary to take the antibiotics for four to nine months typically. (5,12)

The two most common regimens for active TB disease, where TB is not drug resistant, are:

• The four-month TB treatment regimen, which consists of a high-dose daily rifapentine (Priftin) with moxifloxacin (Avelox), isoniazid (Nydrazid), and pyrazinamide
• The six- to nine-month RIPE TB treatment regimens, which consist of rifampin (Rifadin), isoniazid (Nydrazid), pyrazinamide, and ethambutol (Myambutol)

One major concern in the treatment of active TB is making sure people continue to take the medication even after symptoms have gone away. People typically need to take medication for many months, so they often get tired of it and forget, says Robert Amler, MD, dean and professor of public health at New York Medical College in Valhalla, New York.

Stopping the drugs early can cause the TB bacteria to return, and that bacteria may not respond to drugs that worked the first time. This is called drug-resistant TB, and it’s much harder to treat.

To make sure people with active TB finish the full medication schedule, directly observed therapy, or DOT, is used. In DOT, a trained healthcare worker provides each dose of medication, watches the patient swallow it, and documents that the medication has been taken.

Resources We Love

Centers for Disease Control and Prevention
World Health Organization
American Lung Association