Prior to the COVID-19 pandemic, tuberculosis (TB) killed more people in the world than any single infectious disease. In 2021, SARS-CoV-2, which causes COVID-19, surpassed TB. However, it is anticipated that as we move away from the pandemic, newer data will return the deadliest infection title to TB. Each year, about 10 million people around the world are infected with TB and about 1.2 million die. This statistic becomes even more heartbreaking when you realize that TB is both preventable and curable. 

Cases of TB occur in the U.S. each year, but most are diagnosed in people not born in the U.S. Annual cases have been going up since 2021, increasing from about 7,900 cases in 2021 to about 10,350 cases in 2024. The number of deaths each year has been between 500 and 600.

The TB vaccine is rarely used in the U.S. In most other countries, the vaccine for tuberculosis, known as the BCG vaccine, is used more commonly because of the frequency of disease.

The disease

What is tuberculosis?

Tuberculosis (TB) is caused by a bacterium, known as Mycobacterium tuberculosis. The infection primarily attacks the lungs. The bacteria are so destructive that infected people commonly cough up mucus and blood. Children less than 5 years of age can have a severe, often fatal, form of TB, called "miliary" TB. Miliary TB results when the bacteria spread to many parts of the body, including the lining of the brain (meninges).

TB is highly contagious. The bacteria spreads through coughing, sneezing, talking and singing. Many people who are infected don't get sick right away. Instead, the bacteria live without reproducing or causing symptoms for years, even decades. When someone has the inactive bacteria in their body, they have “latent TB.” If the bacteria reactivate, the person will develop lung disease and the characteristic cough associated with TB. This is called “active TB.”

What are the symptoms of TB?

People with latent TB do not usually have symptoms unless the bacteria reactivate to cause active TB.

Active TB causes different symptoms depending on the area of the body where the infection is occurring. In most people the infection occurs in their lungs, causing:

• Coughing that lasts for weeks and contains blood or mucus
• Chest pain
• Weakness and fatigue
• Loss of appetite and weight loss
• Chills, fever or night sweats

Notably, children tend to have less severe symptoms, such as a cough that does not produce blood or mucus.

Other parts of the body that can be affected include:

• Lymph nodes, causing hard, painless red- or purple-colored sores under the skin
• Kidneys, causing blood in urine
• Lining of the brain, causing inflammation (meningitis), headache or confusion
• Spine, causing back pain
• Voice box or larynx, causing hoarseness

Who is at risk for TB?

Anyone can be infected with the bacteria that cause TB, but those at increased risk for an infection include:

• People born in a country with large numbers of infected people
• People in congregate living facilities, including homeless shelters and prisons
• People living with an infected person who cannot be treated with antibiotics or who is infected with antibiotic resistant types of TB

People with latent TB, meaning the Mycobacterium tuberculosis bacteria are living in their body but not reproducing, are at the greatest risk for active TB. It is estimated that about 2 billion people around the world have latent TB infections. In the U.S., the estimate is about 13 million people. 

Within this group of people living with the bacteria, some are more likely to develop active disease, including:

• People recently infected with the bacteria
• People with weakened immune systems from treatments or conditions, such as HIV, diabetes and cancer

How is TB diagnosed?

People can be tested for TB in two ways:

• TB skin test — A small amount of material is put under a person’s skin, and they return to the healthcare provider in two to three days to have the area evaluated for a reaction. This test is sometimes called a “purified protein derivative,” or PPD test.
• TB blood test — A small blood sample is drawn from the person. The blood is mixed with a small amount of TB proteins at the lab to see how immune system cells in the blood respond. 

If a person was vaccinated against TB, the blood test is the recommended choice because the skin test is more likely to result in a false positive. While most people in the U.S. do not get vaccinated against TB, many people in other countries do.

If a person’s TB test is positive, they will be recommended to get a chest X-ray to determine if their lungs show evidence of an active TB infection. 

How is TB treated?

About 5 or 10 of every 100 people living with latent TB will go on to develop active TB during their life if they are not treated. But not all people are recommended for treatment. Usually those at highest risk for development of active disease are treated with a series of antibiotics. This decision is usually made in concert with public health officials or healthcare providers with experience treating TB because the treatment is long (months), requires several different medications, and often results in side effects. Concerns about antibiotic resistance, which is when the bacteria change so they are no longer stopped by the antibiotic treatment, are also a factor.

People with active TB are treated with antibiotics. They usually take multiple medications for a period of four to six months or longer. If people with active TB do not follow the instructions for these medications, they may get sick again, and the bacteria may become resistant to treatment.  

Is TB increasing in the U.S.?

Cases of TB started to increase in the U.S. in the 1980s when the HIV epidemic began because people with HIV have weakened immune systems. As we got better at treating HIV, cases of TB started to slowly decline, beginning around 1993. A larger decrease was observed during the COVID-19 pandemic, likely due to decreased interactions among people. But since 2021, cases have been increasing each year.