Tuberculosis (TB): Causes, Symptoms, Diagnosis and Treatment

Key takeaways:

• Tuberculosis (TB) is a bacterial infection that usually affects the lungs, kidneys, spine, and brain. When someone with active TB coughs, speaks or sings, people nearby may breathe in the germs and become infected.
• There are three stages of tuberculosis: primary, latent, and active. Anyone with a latent TB infection will not experience the symptoms of TB and cannot spread the germs to others. If the immune system is too weak to stop the TB germs from multiplying, the disease becomes active, and in the active stage, it can be fatal without treatment.
• Babies, children, and older adults are at higher risk of developing tuberculosis. But with the right treatment, it can be cured. Treating the disease and preventing its spread to other people is necessary.

There are different possible reasons why a person would persistently cough up blood droplets, alongside other symptoms like weight loss. One such reason is a bacterial infection called tuberculosis (TB). TB is contagious and spreads through the air when an infected person coughs, sneezes, spits, or talks.

Tuberculosis is a known disease worldwide. About 25% of the global population has been infected by Mycobacterium tuberculosis, the bacteria that causes TB. However, more than 80% of TB cases and deaths are in low and middle-income countries.

In 2023, about 87% of new tuberculosis cases occurred in countries like Bangladesh, China, the Democratic Republic of the Congo, India, Indonesia, Nigeria, Pakistan, and the Philippines.

What is tuberculosis?

Tuberculosis (TB) is an infection usually contracted by inhaling tiny droplets of Mycobacterium tuberculosis bacteria from the coughs or sneezes of someone with an active infection. TB spreads, especially when the infected person’s immune system cannot effectively fight the bacterium. 

Most people infected with the TB bacteria don't have symptoms yet. However, symptoms usually include cough (sometimes blood-tinged), night sweats, fever, and weight loss. In some cases, TB can resist drugs and requires special treatment with multiple antibiotics.

Who is affected by tuberculosis?

More than 30 million deaths have been attributed to TB since the World Health Organization (WHO) called it a global emergency in 1993.

Anyone can contract tuberculosis, but the following people are at a higher risk of developing it: , ,

• People with medical conditions like diabetes (high blood sugar)
• People with weakened  immune systems, such as those with unmanaged HIV or AIDS, older adults, and babies
• People who are malnourished
• Individuals who excessively consume alcohol, tobacco, or tobacco products
• People assigned male at birth

TB can be fatal, but it can be avoided with proper care and immunization. Treatment is also available to cure it. This means death from tuberculosis is preventable.

The stages of tuberculosis

Being infected with TB bacteria and having active tuberculosis disease are two different cases.

This could be differentiated based on the stage of TB development, which are:

• Primary infection (exposure)
• Latent TB infection (inactive TB)
• Active TB (TB disease)

Primary infection (exposure)

Primary TB infection occurs when a person has been exposed to or in contact with another person with TB. The individual will have a negative skin test, a normal chest X-ray, and no disease symptoms. After this stage, the infection can either enter a latent stage or become active.

Latent tuberculosis infection (inactive TB)

The latent TB infection stage happens when a person has TB bacteria but no disease symptoms. The infected person's immune system fights off the TB germs, and the TB stays inactive. 

The person may have a positive skin or blood test for TB but a normal chest X-ray. They will also have no sign of active infection in other body parts. Usually, there are no symptoms, but treatment, which typically involves a medication regimen, will still be required. 

This latent TB stage may last weeks or years before progressing into an active infection, or it may remain as a latent infection.

Active tuberculosis (TB disease)

In the case of active TB, the person has signs and symptoms of an active TB infection. The person could have a positive or negative skin or blood test for TB and a positive chest X-ray, sputum culture, lung biopsy, or other findings showing an active infection.

While TB usually enters and stays in the latent infection stage, some people develop an active infection when their immune systems weaken. 

Occasionally, other people may develop an active TB infection right away. As this happens, the bacteria may replicate and cause symptoms, resulting in active TB.  Without medical intervention, TB becomes active in 5–10%of people with the infection.

What causes tuberculosis?

Tuberculosis (TB) is caused by a bacterium (germ) called Mycobacterium tuberculosis.  When someone nearby inhales the expelled droplets, which contain TB bacteria, he or she becomes infected. 

The TB germ may settle in the lungs and grow or move through the blood to other body parts, such as the kidneys, spine, and brain. TB disease advances when the bacteria affect different organs and spreads easily to others without their knowledge, as its symptoms may be mild for an extended time. 

Symptoms of tuberculosis

Generally, the symptoms of active tuberculosis disease depend on the body parts affected; for instance:

• TB disease of the lungs can cause a range of symptoms, including chest pain, breathlessness, and severe coughing.
• TB disease of the kidney may lead to traces of blood in the urine.
• TB disease of the lymph nodes may cause red swelling under the skin.
• TB disease of the spine can cause back pain.
• TB disease of the brain (meningitis TB) may cause headaches or confusion.
• TB disease of the larynx may cause hoarseness.

However, the following are the most common symptoms of active TB, though, each person may experience such symptoms differently:

• Cough that lasts 3 weeks or longer  (prolonged / persistent cough). 
• Coughing up blood or sputum 
• Chest pain
• Weakness/fatigue
• Loss of appetite
• Unexplained weight loss
• Poor growth in children
• Intermittent low-grade fever 
• Bone pain
• Chills or night sweats.

How tuberculosis spreads

TB germs can stay in the air for several hours, depending on the environment. If an individual breathes in these germs, he or she becomes infected. 

TB bacteria spreads more in enclosed areas and places with poor ventilation (such as closed vehicles) than outdoors. Usually, one would have to spend longer periods in close contact with an infected person to catch the infection. 

TB can spread from one person to another when a person with active TB disease:

• sneezes

• coughs

• talks

• shouts

• sings

• spits

• blows out air

When another person inhales the particles, the bacteria may enter their lungs or other body parts. TB in the kidneys, spine, or brain is generally not transmissible to others. It is typically only infectious if it is in the throat or lungs.

People with active TB can transmit the infection. However, most individuals with the disease can no longer transmit the bacteria after receiving appropriate treatment for at least 2 weeks.

It is important to note that TB germs are not spread by:

• Shaking hands with someone
• Sharing or eating food together
• Touching toilet seats
• Sharing comb with someone
• Kissing.

How doctors diagnose tuberculosis

Doctors typically ask questions about an individual’s symptoms and medical history to diagnose tuberculosis. This aims to determine if the person might have been exposed. The next steps include:

Physical examination

A physical examination (check) may be performed. This involves listening to the lungs using a stethoscope and checking for swelling in the lymph nodes (the neck).

Investigation (tests)

If TB is suspected, doctors will often order for TB tests, especially:

• If the person has spent time with someone who has TB 
• Has spent time in a country with high rates of TB  
• Worked in an environment where TB may be present.

Usually, two tests can show whether TB bacteria are present. They are: 

• TB skin test (Mantoux test): The skin test is carried out by injecting a small amount of tuberculin (a fluid substance) into the skin of the arm. This liquid will cause a small reaction on the skin if the person has TB.The doctor will usually tell you to return within 48 to 72 hours to check if a bump  (thickening) of the skin has formed. 
• TB blood test: The TB blood test involves examining a blood sample in the laboratory to determine whether you are infected and to check how your immune system reacts to the germs that cause TB.

However, these two tests cannot indicate whether TB is active or latent. To test for active TB disease, the doctor may recommend a chest X-ray to look for visible signs of TB in your lungs and a sputum test (coughed-up mucus) to check for the bacteria. These tests can take one to two months before results are available.

WHO also recommends fast diagnostic tests, such as the Xpert MTB/RIF Ultra and Truenat assays. These tests are highly accurate and necessary for the early detection of TB and drug-resistant TB. However, they can be complex and expensive.

Treatment for tuberculosis

Anyone with TB needs treatment, whether the infection is active or not.With early detection and appropriate antibiotics, TB is treatable. The most common antibiotics used for treating tuberculosis are: 

• Rifampin (RIF)
• Isoniazid (INH)
• Pyrazinamide (PZA)  
• Ethambutol (EMB). 

The right type of antibiotic and length of treatment mostly depends on the following:

• Age and overall health of the person
• If the patient has latent or active TB
• The location of the TB infection
• Whether the TB strain is drug-resistant

Treatment of latent TB

According to the US Centers for Disease Control and Prevention, treatment for latent TB can vary. It may involve someone taking the antibiotic - Isoniazid (INH), Rifapentine (RPT) and Rifampin (RIF), mostly ranging from once a week for 12 weeks or every day for 9 months.These medications could be used on their own or in combination with another.  

Treatment of active TB

Treatment for active TB may involve a combination of antibacterial medications {Rifampin (RIF), Isoniazid (INH), Pyrazinamide (PZA), and Ethambutol (EMB)}, for 6–9 months. 

Active TB treatment mostly includes a 2-month intensive phase followed by a continuation phase of 2–4 months. 

During the intensive phase, TB organisms are rapidly killed to hinder disease progression, transmission, and development of drug resistance. In the continuation phase, dormant organisms are eliminated to cure and prevent recurrence. 

TB treatment with ethambutol – mostly depends on the presence of HIV, isoniazid resistance, severity of disease, and age. 

Depending on the parts of the body affected, the doctor may prescribe corticosteroids (a class of drugs that can reduce inflammation, suppress overactive immune system responses, and help with hormonal imbalances).

Treatment of drug-resistant TB

When a person has a drug-resistant strain of TB, the treatment will be more complex. You must complete the full course of treatment, even if you no longer experience symptoms. 

If you stop taking your medication early, some bacteria can survive and become antibiotic-resistant.  When this happens, you may go on to develop drug-resistant TB. 

Drug-resistant TB means that some drugs initially used to treat TB will no longer be able to fight the TB germs in your body. TB that is resistant to more than one drug, called multidrug-resistant TB (MDR TB), is very dangerous. 

The treatment for this type of TB takes much longer to complete, and you may experience more side effects.There are various treatment regimens for TB, which can last for 4, 6, or 9 months, depending on the drugs prescribed and the frequency and dose of the drugs.

Drug combinations for the 4 months TB treatment regimen include:

• Moxifloxacin (MOX),
• Isoniazid (INH)
• High-dose daily rifapentine (RPT)
• Pyrazinamide (PZA)

On the other hand, drugs combination for the 6 and 9 months TB treatment regimen (RIPE) include:

• Rifampin (RIF),
• Isoniazid (INH),
• Pyrazinamide (PZA), and
• Ethambutol (EMB)

How to prevent tuberculosis

The Bacille Calmette-Guérin (BCG) vaccine is given to babies or small children—as part of a regular immunization program to prevent TB in certain countries. It protects children from serious forms of TB.

Workers who are at risk of contracting TB should be tested regularly. The best way to prevent the disease is to treat it once infection occurs. 

Below are steps taken to prevent the spreading of TB germs to other people:

• Covering your mouth when you cough or sneeze and wearing a face mask
• Staying away from people at risk of infection
• Seeking medical attention once you notice symptoms like prolonged cough and unexplained weight loss.
• Getting tested for TB if you are at increased risk (e.g., if you have HIV)
• Ensuring you stay in places with proper ventilation

When to seek medical care

You should seek medical care if you have any of the following symptoms:

• A prolonged cough
• Unexplained weight loss
• Fever or night sweats that don't go away
• Loss of appetite
• Feeling tired
• Phlegm (slimy mucus, usually expelled by coughing) with blood in it
• Neck swelling
• Chest pain.
• Bone pain 

Usually, an individual with latent TB will have no symptoms. Therefore, you should also seek medical care if you think you might have been exposed to TB, especially if you've spent much time with someone who has TB or worked in a healthcare facility with possible exposure.

Also, someone with HIV has a higher risk of developing TB than someone with a healthy immune system. Therefore, he or she should seek medical care.