Tuberculosis is an infectious disease caused by bacteria that attack mainly the lungs. The disease can be spread to other people by droplets released into the air through coughing and sneezing.

A tuberculosis infection may be latent, in which the infected person carries the bacteria, but shows no symptoms and cannot spread the disease; this results from the body’s immune system being able to prevent the bacteria from growing. Tuberculosis bacteria, however, can reactivate and start to multiply causing the person to go from having a latent tuberculosis infection to having active tuberculosis disease.

Anyone living or travelling to areas where tuberculosis is common is at risk of developing the disease, but certain groups, such immunocompromised people, are at a higher risk of the disease than others.

When the bacteria that causes tuberculosis enter the air sacs in the lung, a type of white blood cells known as alveolar macrophages destroy or inhibit most of the bacteria by engulfing them. Tuberculosis at this stage is latent. Inside the macrophages, a small number of bacteria may continue to multiply at a slow rate. When the macrophages die, bacteria still alive may start to multiply rapidly and overcome the immune system, causing the infection to become active.

Tuberculosis causes a cough that lasts for at least 3 weeks, in addition to a fever and fatigue, but the disease is usually diagnosed through skin or blood tests that detect evidence of the disease. other tests include sputum tests and imaging scans of the chest.

Mycobacterium tuberculosis has many strains known for their resistance to most of the antibiotics used to treat the disease; therefore, treatment usually involves taking a combination antibiotic for a long period of time. Latent tuberculosis, however, may require taking a single antibiotic.

Tuberculosis can lead to many complications if left untreated. These complications can be related to the respiratory tract, such as inflammation of the larynx and the bronchi, but the bacteria can also spread to other parts of the body and affect the kidneys, liver and brain.

People can reduce their risk of contracting tuberculosis by avoiding contact with patients who have the active disease. A patient with tuberculosis disease will remain contagious for 3 weeks after treatment has started, but usually no isolation is required because the patient can prevent spreading the bacteria to others by following simple precautions, e.g. covering the mouth when sneezing and coughing.

Despite being potentially lethal, tuberculosis can be cured in most patients with proper treatment. The disease may remain dormant in some patients who were cured and reactivate years later. Cases of drug-resistant tuberculosis, and HIV\AIDS patients who contract the disease are harder to treat.

The World Health Organization (WHO) and the US Centers for Disease Control and Prevention (CDC) reported that over 2 billion people are infected with latent tuberculosis around the world, with around 10 million cases becoming active in 2015.

Tuberculosis is a serious infectious disease caused by bacteria called Mycobacterium tuberculosis that infects the lungs. The disease is both preventable and treatable, but is still a potentially deadly disease.

Tuberculosis is usually divided into two categories:

Latent Tuberculosis Infection

Many people have tuberculosis, but show no symptoms; the bacteria are in the lungs but they remain inactive. Treatment is very important if latent tuberculosis is detected because the infection can become active and contagious.

Active Tuberculosis Disease

Having an active tuberculosis disease means that the bacteria are rapidly multiplying in the lungs and are causing symptoms. Tuberculosis usually becomes active a few weeks after infection, but it can take several years to activate.

Tuberculosis is caused by bacteria spread in the air from one person to another. Although the disease spreads with coughs and sneezes, it does not spread quickly and easily; a person usually has to be in close contact with a patient for a long period of time for the infection to spread, so it usually spreads between family members, co-workers or close friends.

Anyone can contract tuberculosis, but certain factors put people at a higher risk of the disease than others. People at the highest risk are:

• Some people’s bodies cannot fight infections properly due to weakened immunity from diseases, such as HIV/AIDS, or using some medications that affect the immune system. Young and elderly people have weaker immunity so they are also more at risk.
• People who live in or travel to regions where rates of are high. Africa, Eastern Europe and Latin America are some examples of regions with high levels of tuberculosis.

People who have to be in close contact with patients who have tuberculosis are at a high risk of developing it themselves. This includes people who work in hospitals and people who care for a family member or a friend with the disease.

Tuberculosis begins when droplets that contain bacteria of the Mycobacterium tuberculosis species enter the body. Tuberculosis is difficult to catch because almost all the bacteria are trapped in the upper respiratory tract, and are then pushed out with mucus by small, hair-like structures on the surface of the tract called cilia.

Bacteria, however, may escape this first line of defense and reach the air sacs, or alveoli, in the lungs. When the bacteria enter the alveoli, they are quickly engulfed and ingested by a type of white blood cells known as alveolar macrophages that destroy or inhibit most of the bacteria, keeping them under control. At this stage, tuberculosis is called latent and causes no symptoms and cannot be spread to other people.

A small number of bacteria may continue to multiply at a slow rate inside the macrophages and are released when macrophages die. If the bacteria released remain alive, they may start to multiply rapidly and overcome the immune system, causing the infection to become active. At this point, the infection may spread to other parts of the body, such as the kidneys and brain, causing extrapulmonary tuberculosis.

Active tuberculosis may lead to the following signs and symptoms:

• Coughing that lasts for 3 or more weeks, and may be bloody and bring up phlegm
• Pain in the chest, which may result from breathing or coughing
• Weakness or fatigue
• Appetite and weight loss
• Fever
• Night sweats

There are two main methods to test for and diagnose tuberculosis:

Tuberculosis Skin Test

This test, also called Mantoux test and tuberculin skin test, involves injecting a substance known as tuberculin into the skin of the forearm and then wait for 48 to 72 hours. If a skin reaction develops at the site of injection, the person is likely to have a tuberculosis infection.

Tuberculosis Blood Test

Blood testing for tuberculosis, also called interferon-gamma release assays (IGRAs), uses a sample of blood to look for gamma interferon that is released by white blood cells when they are exposed to tuberculosis antigens.

Other tests may be used to confirm the diagnosis or plan for treatment. These include:

Imaging Tests

Chest X-rays and CT scans help show white spots in the lungs which represent the spots where the immune system has engulfed the bacteria in latent tuberculosis. Imaging tests may also show changes in the lungs associated with active tuberculosis.

Sputum Test

Sputum tests are usually performed when chest X-rays indicate a tuberculosis infection by collecting a sputum sample and testing it for tuberculosis bacteria to confirm the diagnosis. A sputum test can also help detect drug-resistant strains of the bacteria, helping the doctor choose the right treatment course.

Similar to other bacterial infections, tuberculosis is treated with antibiotics, but it differs in that treatment must continue for at least six months. Surgery may sometimes be needed to treat tuberculosis.

Medication

First-line anti-tuberculosis drugs used to treat tuberculosis include:

• Isoniazid
• Rifampicin
• Pyrazinamide
• Ethambutol

The length of treatment and the type of medication used depend on the age of the patient, his\her overall health, and the location of the infection.

Latent tuberculosis is usually treated with a single type of antibiotics, but the active form may require a combination of antibiotics, especially if the strain is drug-resistant. Treatment for drug-resistant tuberculosis may continue for more than a year and a half.

The symptoms of tuberculosis may start to go after two weeks of treatment, but patients should adhere to their medication course and the doctor’s recommendations to prevent a relapse, or prevent the bacteria from developing resistance to the drugs, making the disease more serious and much harder to treat.

A form of tuberculosis disease called multidrug-resistant tuberculosis is caused by bacteria that do not respond to treatment with first-line anti- tuberculosis drugs. This condition is curable, but needs interventions with second-line drugs that are limited, in addition to chemotherapy for an extended period of time.

Surgery

Surgery to remove the diseased part of the lung was performed to treat tuberculosis in the past. Using this type of surgery, called collapse therapy, became less common after effective drug treatments were developed. Now, the use of lung surgery to treat tuberculosis is increasing due to the emergence of drug-resistant strains of the bacteria.

Tuberculosis may spread to other parts of the body and cause other complications:

• Back pain: Tuberculosis can reach the spine and cause back pain and stiffness.
• Tuberculosis arthritis: Joint inflammation and pain can result from tuberculosis spreading to joint. The hips and knees are usually affected.
• Meningitis: Tuberculosis can spread to the brain and cause the membranes that cover it to swell. Swelling of these membranes causes headaches and may lead to mental changes.
• Decreased liver or kidney function: Tuberculosis may spread to the liver or kidneys, which affects their function in filtering waste from the blood.
• Cardiac tamponade: Tuberculosis can infect tissue surrounding the heart in rare cases. This causes inflammation and fluid build-up that affect the heart’s ability to pump blood effectively.
• Enteritis: Enteritis is inflammation of the small intestine, and may result when sputum containing tuberculosis-causing bacteria are swallowed.

Vaccines can greatly protect children from tuberculosis, but the protection it provides is variable in adults; therefore the best way to prevent tuberculosis for adults is to avoid as much contact as possible with patients who have the active form of the disease.

Latent tuberculosis can be prevented from becoming active by receiving the proper treatment and adhering to the doctor’s guideline.

Patients with active tuberculosis can help prevent it spreading to others by:

• Not going to school or work in the first few weeks after treatment has started. Sleeping alone in the room can also contribute reducing the risk of transmission.
• Keeping rooms well ventilated if possible can help reduce the risk of transmitting tuberculosis to other people.
• Patients with active tuberculosis should cover their mouth and nose with a tissue when sneezing and coughing. Used tissues should be immediately thrown in the trash.
• Patients with tuberculosis are advised to wear a surgical mask to reduce the chance of spreading the disease to others.

Although the treatment course for tuberculosis is lengthy, the disease can be cured in most patients who receive and adhere to their treatment regimen, but without proper treatment, the disease can be potentially fatal. The disease may remain dormant in some patients who were cured and reactivate years later.

The prognosis of the disease is worse in cases that are difficult to treat, e.g., patients with HIV/AIDS and patients with drug-resistant strains.

Tuberculosis is potentially lethal, especially for people with a compromised immune system. Numbers released by the WHO and the CDC show that, globally, over 2 billion people are infected with tuberculosis, with around 10 million cases becoming active in 2015.

The CDC reported that the disease was responsible for 1.8 million deaths worldwide in 2015. In the same year, the WHO reported that 35% of HIV deaths were caused by tuberculosis. If no proper treatment was administered, almost all cases of tuberculosis disease in HIV-positive patients lead to death.