Tuberculosis (TB): symptoms, testing and treatment, a review

Tuberculosis, or TB, is an infection that mainly affects the lungs. It is a serious illness, but it can be treated, and finishing the full course of treatment is the key. India has the largest number of TB cases in the world, so knowing the signs matters. This article uses information from the World Health Organization (WHO), the NHS and the US CDC.

1. Introduction

TB is caused by bacteria, most often one called Mycobacterium tuberculosis ^[3]. It usually affects the lungs but can also affect other parts of the body such as the kidneys, brain, spine and skin ^{[1, 2]}. WHO says TB is preventable and treatable, and that in 2024 it was the world's leading cause of death from a single infectious agent, killing about 1.23 million people ^[1].

India accounted for about a quarter of all new TB cases worldwide in 2024, more than any other country ^[1].

2. How TB spreads

TB spreads through the air. When a person with active TB disease in the lungs or throat coughs, sneezes, speaks or sings, they release droplets that contain the bacteria. Other people can breathe these in ^{[1, 3]}. The CDC says the droplets can stay in the air for hours, and spread is more likely in closed, poorly ventilated spaces ^[3]. The NHS notes that infection usually needs regular, prolonged contact with the droplets ^[2].

It is important to know the difference between two conditions ^{[1, 2, 3]}:

• Latent TB infection. The bacteria are in the body but are inactive. The person feels well, has no symptoms and cannot pass TB on. WHO says about 5 to 10 percent of infected people go on to develop active disease at some point ^[1].
• Active TB disease. The bacteria multiply and cause illness. The person can spread TB to others, and without treatment it can be fatal.

3. Signs and symptoms

Symptoms often develop slowly and may be mild for months, so people can pass TB on without knowing it ^[1]. Signs of lung TB include ^{[1, 2, 3]}:

• A cough that lasts three weeks or longer, sometimes with phlegm or blood
• Chest pain
• Fever, chills or night sweats
• Constant tiredness and weakness
• Loss of appetite and weight loss

Children may fail to gain weight or grow as expected ^[2]. When TB spreads beyond the lungs, symptoms depend on the part affected. They can include swollen glands, swollen joints, belly pain, headaches, vomiting, confusion and rashes ^[2].

4. Who is at higher risk

Anyone can get TB, but risk is higher for ^{[2, 3]}:

• People in close, long contact with someone who has active TB, such as household members
• People who live or work where TB is common, including health workers and people in crowded settings such as shelters or prisons
• People with a weak immune system, for example from HIV, diabetes, cancer treatment or certain medicines
• Children under five
• People who smoke, drink heavily or use drugs
• People who had TB before that was not fully treated

5. Diagnosis and tests

WHO recommends rapid tests as the first step for anyone with signs of TB. These include molecular tests that give accurate first results within about 48 hours of collecting a sample ^[1]. Doctors may also use chest imaging such as an X-ray, tests on coughed-up phlegm, and sometimes a biopsy of affected tissue ^[2].

For people without symptoms who may have been exposed, there are two main tests ^{[2, 3]}:

• A skin test (the Mantoux test), in which a small amount of testing material is injected under the skin and the reaction is checked after two to three days ^[3]. The CDC says the BCG vaccine can cause a false positive result.
• A blood test (IGRA), which measures the body's immune response to TB bacteria and is preferred for people who have had the BCG vaccine.

The CDC explains that other tests, such as a chest X-ray and a phlegm test, are needed to find out whether a person has inactive (latent) TB or active TB disease ^[3].

6. Treatment

Treatment is with a combination of antibiotics. The NHS says active TB is usually treated for at least six months, and latent TB for three to six months ^[2]. Your doctor decides the exact plan, and in some cases other medicines are added ^[2].

The most important rule is to take every dose for the full length of time, even after you feel better. WHO warns that stopping early or without medical advice is dangerous, because it can allow the bacteria to become resistant to the medicines ^{[1, 2]}.

Drug-resistant TB develops when TB medicines are misused, for example through incorrect prescriptions, poor-quality medicines or stopping too soon. It is still treatable, but it needs different medicines that cost more and cause more side effects. WHO now favours shorter, all-oral regimens for eligible patients ^[1].

7. Prevention and special groups

• See a doctor early for a long-lasting cough, fever or weight loss. Early treatment limits spread ^[1].
• Protect others. People with active TB should cover the mouth and nose when coughing, wear a mask and dispose of phlegm and tissues safely. Special measures such as well-ventilated spaces also help reduce spread in healthcare facilities and other institutions ^[1].
• Screening and preventive treatment. People living with HIV and close contacts of someone with TB should be checked. If preventive treatment is prescribed, complete the full course ^[1].
• BCG vaccine. It is given to infants or young children in some countries, including those where TB is common. It helps prevent severe forms of TB in children but is not used everywhere ^{[1, 3]}.

Infants and young children have a higher chance of developing active disease after infection ^[1]. People living with HIV or diabetes are at higher risk of TB disease, and WHO advises screening for people with HIV ^{[1, 2]}.

8. When to see a doctor

See a doctor if you have a cough lasting more than three weeks, unexplained constant tiredness, a fever or night sweats that will not go away, poor appetite, unexplained weight loss, or close contact with someone who has TB symptoms ^[2]. Get urgent medical advice if you cough up blood ^[2].

Get emergency help for a stiff neck with severe headache, pain from bright light, a seizure, sudden confusion or weakness in part of the body, because these can be signs that TB has reached the brain ^[2].

In an emergency, call your local emergency number (112 in India, 911 in the United States).

9. Conclusion

TB is an airborne infection that mostly affects the lungs. It is serious, but it is treatable when found early and when the full course of treatment is completed. Anyone with a cough lasting three weeks or more, fever, night sweats or weight loss should see a doctor without delay.