According to the Centers for Disease Control and Prevention (CDC), one fourth of the world’s population carry the bacteria that cause tuberculosis. Of these, 10.4 million will become sick with the disease each year, and 1.8 million will die. This makes tuberculosis the most deadly infectious disease on the planet.
In this article, we’re going to uncover what causes tuberculosis as well as its symptoms, treatment, and ways you can help protect yourself and others from contracting this potentially life-threatening illness.
What Causes Tuberculosis?
Tuberculosis, or TB, is caused by the bacterium Mycobacterium tuberculosis. The disease is transmitted from person to person when an infected individual coughs, speaks, sings, sneezes, laughs, or spits. All of these activities release microscopic droplets into the air that can be inhaled by another person. However, tuberculosis is difficult to catch, and most people contract it from someone they’re in close contact with, such as a housemate or coworker. In addition, people who’ve been on TB medication for at least 2 weeks are no longer able to transmit the disease.
Types of Tuberculosis
As mentioned at the beginning of this article, approximately two billion people are infected with the bacteria that cause tuberculosis, but the vast majority never show any signs of infection. This is because most people’s immune systems are able to prevent the bacteria from causing sickness. For this reason, tuberculosis can be categorized as either latent or active.
In the case of a latent tuberculosis infection, a person is infected with the bacteria, but the bacteria remain inactive and cause no symptoms. This type of TB also isn’t contagious. But latent TB can become active, so treatment is important to protect the individual and to help prevent the infection from spreading to others.
By contrast, active tuberculosis is just as it sounds—active. However, unlike most types of infection, active TB disease may strike a few weeks to years after an individual becomes infected with Mycobacterium tuberculosis.
Risk Factors for Tuberculosis
While anyone can get tuberculosis, some groups have a higher risk of contracting the disease than others. Factors that increase your risk of developing TB include:
- Weakened immune system: Conditions such as human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), diabetes, certain cancers, and malnutrition; medications like chemotherapy and immunosuppressants; and extreme youth or age increase your risk of developing TB.
- Travel history: People who travel to or emigrate from parts of the world with higher rates of TB or drug-resistant TB, including Latin America, the Caribbean, Africa, Asia, Eastern Europe, and Russia, have a greater risk of developing TB.
- Substance abuse: People who smoke tobacco or use intravenous drugs or excessive alcohol have a higher risk of TB.
- Work history: People who work in homeless shelters, correctional facilities, or nursing homes or other health care facilities have a greater risk of developing TB.
- Home situation: People who live with someone who’s infected with TB have a higher chance of developing TB themselves.
While tuberculosis is less common in the United States—with a total of only 9,105 TB cases reported in 2017—according to the World Health Organization (WHO), the number of tuberculosis infections has been rising in many countries since the 1980s due in part to the emergence of HIV. This is because HIV suppresses the immune system, which causes the body to become less able to fight off the TB infection.
In fact, tuberculosis is the leading cause of death among people with HIV, and those with HIV are 26 times more likely to develop active TB disease than those without HIV.
Symptoms of Tuberculosis
Although the bacteria that cause tuberculosis generally grow in the lungs and lead to pulmonary tuberculosis when active, they can spread to other parts of the body as well, including the kidneys, spine, and even brain. Therefore, symptoms may vary; however, symptoms of active TB generally include:
- Cough lasting 3 weeks or more
- Coughing up blood or sputum
- Chest pain
- Pain with breathing or coughing
- Loss of appetite
- Weight loss
- Night sweats
If you’re experiencing worrisome symptoms or think you or a loved one may have been exposed to tuberculosis, it’s important to undergo TB testing as soon as possible. Your health care provider will speak with you about your medical history, examine your lungs while you breathe, and check your lymph nodes for signs of swelling.
If your health care provider suspects tuberculosis, they may then choose to perform either a skin test or blood test. The TB skin test, also known as the Mantoux or purified protein derivative (PPD) tuberculin skin test, involves injecting a small amount of tuberculin PPD just beneath the skin of the inner forearm.
Within 48 to 72 hours, a health care worker trained in evaluating the results of the TB skin test will check your arm for swelling at the injection site. If a hard, raised area is present, it will be measured to determine whether TB infection is likely. Depending on various additional factors, TB is considered likely if the raised area measures between 5 and 15 millimeters.
Because the TB skin test sometimes returns with false results, especially in people who have conditions such as AIDS or have received the bacillus Calmette-Guerin (BCG) vaccine—which is rarely used in the United States—your health care provider may decide to perform a blood test to confirm the results of the skin test or rule out latent or active tuberculosis.
In addition, people with positive skin tests will likely receive a chest X-ray or computed tomography (CT) scan to evaluate the lungs for signs of TB. If imaging shows signs of infection, a sputum sample may also be taken to look for evidence of Mycobacterium tuberculosis.
Tuberculosis Treatment and Prevention
In contrast to most infections, treatment of tuberculosis is extensive. In fact, active TB infections can take 6 to 9 months to successfully treat, and drug-resistant strains of the disease may take 20 to 30 months. The exact length of TB treatment and medications administered will depend on your age, overall health, infection location, and whether the tuberculosis is resistant to certain medications.
Moreover, people with active forms of TB will require treatment with several medications, while people with latent TB infections may need only one or two different drugs. The most common TB drugs used are:
Unfortunately, drug-resistant strains of tuberculosis have been on the rise since the first TB medications were created, and this has helped keep TB a worldwide threat.
Multidrug-resistant tuberculosis (MDR-TB) is resistant to both isoniazid (INH) and rifampin, and a form of tuberculosis known as extensively drug-resistant TB (XDR-TB)—which is a rare type of MDR-TB—is resistant to INH, rifampin, fluoroquinolones, and at least one of the three medications used as second-line treatment (amikacin, kanamycin, capreomycin).
As stated earlier, after approximately two weeks of treatment, people with tuberculosis are no longer capable of infecting others. However, it’s crucial that anyone being treated for TB complete their course of therapy as directed. Otherwise, the TB bacteria may begin to mutate into more resistant and dangerous strains.
While treating tuberculosis is a lengthy and somewhat complicated process, your health care provider can help you find the tools and support services you need to get through it, so be sure to speak with them about any questions or concerns you may have. And if you experience any side effects from the medications used to treat your TB—including nausea, loss of appetite, jaundice, dark urine, or fever without any obvious cause—you should speak with your doctor as soon as possible to address potential liver toxicity.