Tuberculosis (TB) is a contagious airborne disease caused by Mycobacterium tuberculosis, a bacterium that grows and divides inside of cells.
There are two kinds of TB, latent and active.
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In most people, the immune system can contain the bacteria so that they do not replicate and cause disease. In this case, a person will have TB infection but not active disease.
Doctors refer to this as latent TB. A person may never experience symptoms and be unaware that they have the infection. There is also no risk of passing on a latent infection to another person. However, a person with latent TB still requires treatment. About 5% to 10% of infected people who do not receive treatment for latent TB infection will develop TB disease (active TB) at some time in their lives.
The CDC estimate that as many as 13 million people in the U.S. have latent TB.
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The body may be unable to contain TB bacteria. This is more common when the immune system is weakened due to illness or the use of certain medications. When this happens, the bacteria can replicate and cause symptoms, resulting in active TB. People with active TB can spread the infection.
The infection, which starts in the lungs, causes nodules known as tubercles, or Ghon focii, which are spots left by dead infected tissue. With time, the disease can spread to other areas of the lung and larger areas of lung tissue may die off, causing cavities. Bacteria can also spread to other organs, including the kidney, brain, and spine.
The signature symptom of active TB is a bad cough that produces blood-tinged phlegm and can last three or more weeks. Other symptoms include chest pain, fatigue, loss of appetite, weight loss, fever, chills, and night sweats. Symptoms typically worsen over time, but they can also spontaneously go away and return.
TB usually affects the lungs, though symptoms can develop in other parts of the body. This is more common in people with weakened immune systems. TB can also cause:
▪️persistently swollen lymph nodes, or “swollen glands”
▪️abdominal pain
▪️joint or bone pain
▪️confusion
▪️a persistent headache
▪️seizures
People should ask for a TB test if they:
▪️have spent time with a person who has or is at risk of TB
▪️have spent time in a country with high rates of TB
▪️work in an environment where TB may be present
Two tests can show whether TB bacteria are present:
▪️the TB skin test
▪️the TB blood test
However, these cannot indicate whether TB is active or latent. To test for active TB disease, the doctor may recommend a sputum test and a chest X-ray.
Everyone with TB needs treatment, regardless of whether the infection is active or latent.
The right type of antibiotic and length of treatment will depend on:
▪️the person’s age and overall health
▪️whether they have latent or active TB
▪️the location of the infection
▪️whether the strain of TB is drug-resistant
Treatment for latent TB can vary. It may involve taking an antibiotic once a week for 12 weeks or every day for 9 months.
Treatment for active TB may involve taking several drugs for 6–9 months. When a person has a drug-resistant strain of TB, the treatment will be more complex.
TB is not something that is typically vaccinated against in the United States and it can be fatal if left untreated.
TB has been around for tens of thousands of years. It was often called "consumption" because of the dramatic weight loss it can cause. Before the 1940s, when the antibiotic streptomycin became available, there wasn't much that could be done for the illness. Fresh air, good nutrition, and sunlight were thought to be helpful but didn't always work. In some cases, doctors attempted to remove a diseased lung. From the 17th through the 19th centuries, it is believed that one in five people died from tuberculosis.
It wasn't until 1882 that TB was identified. Robert Koch isolated and cultured Mycobacterium tuberculosis. He immediately began to work on a vaccine for treatment and prevention of tuberculosis.
Between 1904 and 1921 Albert Calmette and Camille Guérin worked on attenuated tuberculosis bacilli to test on humans. They used TB from cows to weaken the bacteria enough to place in humans in hopes of providing some immunity. Their preparation is called Bacillus Calmette-Guérin, or BCG in shorthand.
In 1928, the Health Committee of the League of Nations adopted BCG as a recommended tuberculosis vaccine. Between 1947 and 1951 a total of 8 million babies and nearly 14 million people were given the BCG vaccine in the International Tuberculosis Campaign. The project initially began in Europe in the aftermath of World War II. However, the program extended beyond Europe when UNICEF contributed $2 million to expand the program to other continents.
In 1974 WHO included BCG in the list of recommended vaccines for developing countries. In 1974 fewer than 5% of children worldwide were immunized by age 1 against diphtheria, polio, tuberculosis, pertussis, measles, and tetanus. The Expanded Programme on Immunization would help bring vaccination against these six diseases to many underserved areas.
Still a leading killer worldwide, tuberculosis is less prevalent in the United States than it used to be. According to the CDC, 9,029 new cases of TB were reported in the United States in 2018.
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