What Is Tuberculosis? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Tuberculosis, or TB, is an infectious disease caused by the bacteria Mycobacterium tuberculosis. The bacteria spreads through the air from person to person and mainly attacks the lungs, but it can affect other areas of the body, according to the American Lung Association. (1)

The disease has been around for most of human history, becoming particularly deadly at times. In fact, researchers can trace tuberculosis back to early Egypt, more than 5,000 years ago. There is also mention of TB in the biblical books of Deuteronomy and Leviticus under the Hebrew word schachepheth, and Hippocrates describes it in his writings as "phthisis." (2,3)

It’s possible that M. tuberculosis could have killed more people than any other microorganism. Tuberculosis was an epidemic in industrialized Europe and North America during the 18th and 19th centuries. During those times it was known as "consumption." (2)

The development in the 1940s of streptomycin, the first antibiotic to effectively cure TB, dramatically lowered the number of cases of tuberculosis seen in developed countries, including the United States. (2,3)

The majority of people exposed to the bacteria don’t experience tuberculosis symptoms right away. Instead, the infection may go through three stages:

• Primary TB Infection This is when the bacteria first enters your body. In many people this causes no symptoms, but others may experience fever or pulmonary symptoms. Most people with a healthy immune system will not develop any symptoms of infection, but in some people the bacteria may grow and develop into an active disease. Most primary TB infections are asymptomatic and followed by a latent TB infection, according to the Centers for Disease Control and Prevention (CDC). (4)
• Latent TB Infection The bacteria is in your body and can be found through tests, but is not active. During this stage you don’t experience symptoms and can’t spread the disease to others, notes MedlinePlus. (5)
• Active Disease The TB bacteria are active and multiplying. You’ll feel sick and will be contagious. It’s important to seek immediate treatment to avoid complications and infecting others. (5)

The vast majority of people don’t have a problem because the organism enters their body and is then handled by their immune system, says Robert Amler, MD, dean of the School of Health Sciences and Practice and vice president for government affairs at New York Medical College in Valhalla, New York.

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 as a result of malnutrition, old age, infection with HIV, immunosuppressant drugs, or among people who are on dialysis. (1,5,6)

TB can also be caused by the bacteria Mycobacterium bovis, which lives in animals and can be transmitted to children who drink unpasteurized milk from infected cows. In the United States, cattle are tested for tuberculosis, and most milk is pasteurized, notes the CDC. (7)

Many people with TB won’t know they have it unless they get tested because there won’t be any symptoms from latent TB. About one-quarter of the world's population has latent TB, according to the World Health Organization (WHO). (8) That’s why it’s important to get screenings if you believe you’ve been exposed to TB.

Once TB becomes active, you’ll begin to notice symptoms. But symptoms may not show up in full force right away. The first thing you may notice is a bad cough that doesn’t go away, or chest pain. These symptoms are easy to dismiss or mistake for another condition, so it’s important to see your doctor if you were diagnosed with latent TB before or have recently been exposed to someone with active TB. (1,5,8)

The symptoms of active tuberculosis include: (5,6,9)

• A general sense of being unwell
• Coughing
• Coughing up blood or phlegm
• Chest pain
• Trouble breathing
• Loss of weight and appetite
• Night sweats
• Intermittent fever
• Generalized body aches
• Fatigue

Learn More About Signs and Symptoms of Tuberculosis

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. (1,4)

The bacteria do not live on surfaces, so you can’t get TB by:

• Shaking hands
• Using a toilet
• Sharing drinking glasses or eating utensils
• Touching other surfaces

People with a weakened immune system have the highest risk of getting infected with TB. (10) “We particularly worry about people with HIV or AIDs because their immune system can be overwhelmed by TB,” says Dr. Amler.

Risk factors for TB include:

• Poverty
• HIV infection
• Homelessness
• Being in jail or prison (where close contact can spread infection)
• Substance abuse
• Taking medication that weakens the immune system
• Kidney disease and diabetes
• Organ transplants
• Working in healthcare
• Exposure to air pollution
• Cancer
• Smoking tobacco
• Pregnancy
• Age, specifically babies, young children, and elderly people

When active tuberculosis is diagnosed in the United States, it's often in a person who has emigrated from or traveled to a country with a much higher rate of TB.

People with a normal, healthy immune system probably don’t have to be worried much about tuberculosis because catching TB is relatively hard, according to Lee Reichman, MD, professor of medicine and epidemiology and executive director emeritus of the Rutgers Global Tuberculosis Institute in Newark, New Jersey. “There’s a higher chance of catching parasites in Africa than TB,” according to Dr. Reichman. It’s also unlikely you’ll be close enough to inhale the air of someone with TB during travel, he says.

Learn More About Risk Factors for Tuberculosis

Diagnosing tuberculosis can be a complex process. Doctors will first consider a person’s history and the likelihood they were exposed to someone with active disease. Then a series of screenings and tuberculosis tests may be needed in order to confirm TB and decide on a course of treatment.

Since latent TB has no symptoms and fewer bacteria are present, it can only be found through a couple screening tests.

The first test used to find TB is called the tuberculin skin test, also known as the Mantoux test or PPD (purified protein derivative). A solution made from TB bacteria is injected in the top layer of skin on the forearm. The person will then return in 48 or 72 hours to have the injection site examined. If there is a red, raised bump larger than 5 to 15 millimeters, a TB infection could be present. But this test isn’t a perfect science. Sometimes results can be wrong, showing false positives or false negatives. (5,11)

A blood test can provide more conclusive results. The interferon gamma release assay (IGRA) test measures the body's immune response to the presence of M. tuberculosis. The test is done in a lab after a blood sample is drawn.

If initial screenings come back positive, further testing is needed to diagnose active TB. Additional lab tests can determine which strain of TB bacteria a person has and which antibiotics are most effective. Imaging gives more information on where the disease is located and how it’s affecting the body.

Diagnostic tests used for active TB include: (5,11)

• Sputum Samples Sputum is the mucus that comes up when you cough. Samples of sputum can be directly examined in a lab for M. tuberculosis.
• Molecular Tests These can be used to detect the bacteria's genetic material and help identify which antibiotics will work best.
• Biopsy A biopsy of the lungs, lymph nodes, or other tissues may be cultured to grow the bacteria and make it easier to see under a microscope.

Imaging tests used for active TB include:

• X-Rays Chest X-rays may be done to look for signs of TB in the lungs.
• Computerized Tomography (CT) Scans CT scans may be used to look for TB in the spine or to get better views of the lungs if X-ray images are unclear.
• Magnetic Resonance Imaging (MRI) An MRI of the spine or brain may be done if doctors think the tuberculosis infection has spread to those areas.
• Bone Scans These can be used to tell the difference between cancerous lesions and those caused by TB.

Learn More About Diagnosing Tuberculosis

While the disease is still a cause of death in many parts of the world, TB is almost always able to be treated and cured in the United States. But it requires careful adherence to the instructions on how to take medication, in order to eliminate all the bacteria and avoid developing drug resistance, according to the CDC. (12)

TB bacteria takes a long time to be killed off, so treatment can last for six months or longer. People with latent TB will probably only need to take one or two drugs, while those with active TB may need a combination of three to four.

Per the CDC, the most commonly used drugs are: (13)

• Rifapentine
• Moxifloxacin
• Isoniazid
• Pyrazinamide
• Rifampin
• Myambutol (ethambutol)

Remembering to take medicine for such a long period of time can be challenging. One of the biggest worries during TB treatment is people stopping their medication before all the bacteria dies. The leftover bacteria can continue to grow and become resistant to antibiotics. This makes the disease much more dangerous and harder to treat. (12)

Active TB is contagious, making it a public health concern. For that reason, directly observed therapy (DOT) is used to make sure a person is taking their medicine. DOT means a trained healthcare worker provides each dose of medication, watches the patient swallow it, and documents that the medication has been taken.

The Department of Health will be involved until the end of DOT for active TB, according to Alexea M. Gaffney-Adams, MD, an internist with a subspecialty in infectious disease at Stony Brook Medicine in Stony Brook, New York. “It’s a huge public health risk for someone with active TB to be out in the community not taking medication.”

Learn More About Treatment for TB

A person can have latent TB for years, without having symptoms or becoming sick. But if the bacteria is detected, a course of treatment over three to four months is recommended by the CDC. (14)

Treatment for active TB disease can take six to nine months. It's vital that people with TB disease complete their full course of medication exactly as prescribed. Otherwise, the disease can return and be more resistant to treatment. (13)

Prevention of Tuberculosis

Keeping your immune system healthy and avoiding exposure to someone with active TB is the best way to prevent a TB infection.

Identifying and treating cases of latent TB, before the disease can become active, is also important, particularly in high-risk populations.

To prevent the transmission of tuberculosis in healthcare settings, the CDC’s guidelines recommend that all healthcare personnel be screened for tuberculosis when they’re hired. (15)

Other steps toward preventing the spread of TB include:

• Improving ventilation in indoor spaces so there are fewer bacteria in the air
• Using germicidal UV lamps to kill airborne bacteria in buildings where there are people at high risk of TB
• Using directly observed therapy (DOT), in which people taking medication for TB are monitored by their healthcare providers, to raise the likelihood of successful treatment

Learn More About Preventing Tuberculosis

If left untreated TB can affect other parts of the body, beyond the lungs. Back pain, joint damage, and liver or kidney problems, can result, as can swelling of the membranes around your brain. Ultimately, untreated TB can be fatal, notes Mayo Clinic. (16)

While most people are able to tolerate the drugs well during treatment, TB medication can lead to some complications, as well. It can be hard on the liver. Doctors will monitor your liver function on regular checkups to make sure you’re not in danger of complications. (5,6,12)

The following symptoms are considered serious side effects and should be reported to your doctor: (5,6,12)

• Loss of appetite
• Nausea or vomiting
• Yellowing of skin or eyes (a sign of liver damage)
• Fever that lasts longer than three days
• Fatigue
• Dark-colored urine
• Pain the in the abdominal area
• Tingling in the fingers or toes
• Feeling itchy with no known cause
• Rash on the skin
• Dizziness
• Muscle weakness or aching joints
• Changes in vision
• Changes in hearing, like hearing loss or ringing in the ears

Improving your diet, drinking plenty of water, and getting regular exercise can also help your body recover and avoid adding extra strain on the liver.

Learn More About Living With TB and Avoiding Complications

Even though you may not hear much about tuberculosis, it’s still a common disease affecting many people around the world. About one-quarter of the world’s population is infected with TB, and most cases occur in Southeast Asia, Africa, and the Western Pacific region. In 2021, an estimated 10.6 million people got sick from the disease and 1.6 million died. (8)

These eight countries made up two-thirds of new TB cases in 2020: (8)

• India
  
• Indonesia
• China
• Philippines
• Pakistan
• Nigeria
• Bangladesh
  
• Democratic Republic of the Congo

Worldwide, tuberculosis is the 13th leading cause of death and it is a leading cause of death for people with an HIV infection. According to the WHO, about 187,000 HIV-positive people died from TB in 2021. (8)

Although the rate of TB in the United States is much lower today, it’s still a concern. According to the CDC, up to 13 million people in the United States may have a latent TB infection. (17) Without treatment, about 1 in 10 of those people will become sick with TB disease in the future.

The latest data from the CDC shows that a total of 7,174 TB cases were reported in the United States in 2020. (18)

As mentioned above, certain health conditions increase the risk for TB. They include:

• HIV
• Inflammatory bowel disease (IBD)
• Diabetes

People living with HIV are up to 18 times more likely to develop TB than people without HIV, notes the WHO. (8)

The risk of TB is 2 to 3 times greater in people with diabetes, according to the WHO. (19)

There's also a risk involved with taking certain biologic drugs used to treat autoimmune inflammatory diseases, such as Crohn's disease (an inflammatory bowel disease) or rheumatoid arthritis. Biologic medication that suppresses the immune system can increase the possibility of activating latent TB, according to UpToDate. (20) So it's important to get tested for TB before you start taking these drugs.

Favorite Orgs for Essential Tuberculosis Info

The Centers for Disease Control and Prevention (CDC)

The CDC has a comprehensive site on tuberculosis, including everything from basic info about TB, to how TB affects certain populations, to the latest data and stats and research efforts.

World Health Organization (WHO)

The WHO offers an international perspective on tuberculosis, with data about the disease and the toll it takes worldwide. The WHO is also active in initiatives to end TB.

Mayo Clinic

Mayo Clinic provides an up-to-date review of the symptoms, causes, diagnosis, and treatment of TB, as well as info on which doctors treat the disease.

Favorite Orgs for TB Education

Curry International Tuberculosis Center

Located at the University of California in San Francisco, the Curry International Tuberculosis Center has been working to control and eliminate TB in the United States and around the world since 1994. They provide educational resources to the general public and in-depth materials for healthcare professionals as well as those working with at-risk populations.

American Lung Association

For clear, patient-centered information about TB, visit the American Lung Association which has a page on questions to ask your doctor if you're concerned about TB.

Additional reporting by Ingrid Strauch.