Tuberculosis: Causes, Risk Factors, Symptoms, Diagnosis, Treatment, Prevention and Vaccine

It is an infectious disease that generally attacks the lungs, but it can affect other parts of the body as well.

This disease is very contagious, it is spread through droplets of saliva that tuberculosis patients emit when coughing or sneezing.

It is a potentially fatal disease that is caused by different strains of microbacteria .

The condition consists of a chronic cough with blood sputum, fever, night sweats, and weight loss.

Usually diagnosed after a chest X-ray, TB is treated with a combination of antibiotics.

To end this infectious disease, researchers are working on developing new vaccines, as well as developing more effective antibiotics and diagnostic tools.

Tuberculosis mainly affects the respiratory organs (lungs, bronchi, larynx), but it can affect other parts of the body such as bones, kidneys, lymph nodes, meninges. However, only pulmonary tuberculosis is contagious. It is also the most common form of tuberculosis.

Tuberculosis is a communicable disease that must be declared by the doctor to the respective Health department.

Reporting a tuberculosis case to health authorities is essential.

An investigation is triggered in the area where the patient lives or works to define the people who have been in contact with him. Therefore, those in contact will benefit from detection and monitoring.

This exam is free and is carried out by specialized Medico-Social services.

This statement also allows the surveillance of this disease and its evolution in the population.

The Communicable Diseases report is used to monitor the evolution of epidemics and respond quickly by implementing collective protection measures.

Primary infection or latent tuberculosis infection

Primary tuberculosis infection does not show any symptoms or signs on chest x-ray. And it is not contagious.

Koch bacilli can lie dormant in the body for weeks, years, or even decades without causing symptoms or illness.

In fact, if the immune system of the infected person is strong enough, it prevents germs from waking up, multiplying and causing tuberculosis disease. This is the primary infection.

At this stage, the infected person has no symptoms and is not contagious.

Causes and risk factors

The main cause of tuberculosis is Mycobacterium tuberculosis, a small aerobic bacillus without mobility.

In addition to this pathogen, other mycobacteria, such as M. bovis, M. africanum, M. canetti, and M. microti, can also cause tuberculosis.

These pathogens can resist some disinfectants and survive for weeks in a dry environment.

The most important risk factor is HIV in general, since 13% of all people with tuberculosis are also infected with this virus.

Tuberculosis is closely related to overpopulation and malnutrition.

People at high risk include people who inject illicit drugs, prisoners and the homeless, as well as those in charge of social organizations.

Transmission of the disease occurs through droplets of saliva that people with tuberculosis emit when they speak, sing, cough or sneeze.

People living with TB patients have a 22% risk of contracting TB and it is estimated that untreated TB patients can infect 10 to 15 people each year.

Tuberculosis mainly affects urban populations, the elderly, people in precarious situations, migrants and HIV-infected patients.

We speak of a social disease because it preferentially spreads among disadvantaged communities and desocialized people.

HIV and the tubercle bacillus tend to mutually accelerate their progression in the body, the former weakening the immune barriers that generally form a fairly effective resistance against the latter. This association is deadly.

Other conditions and treatments that weaken immune defenses increase the chance of developing latent tuberculosis.

This is the case, for example, of drugs designed to increase tolerance to transplants.


Only the patient with pulmonary tuberculosis can transmit the disease. When a patient coughs, sneezes, talks, laughs, or spits, they throw TB germs into the air.

It is enough that your close environment breathes in a small amount of bacteria to become infected.

Symptoms of tuberculosis

Tuberculosis disease is manifested by symptoms such as fever, severe cough accompanied by sometimes bloody sputum, and chest x-ray signs. This disease is contagious.

When the immune system of the infected person is weakened, the tuberculosis bacillus can resume its activity and multiply.

And latent tuberculosis infection has become active and progressive.

The alterations and manifestations appear gradually in the person who suffers from it and is the sign of the transition to tuberculosis disease.

The causes of weakening of the immune system can be the result of chemotherapy, human immunodeficiency virus (HIV), diabetes, heavy surgery, age-related weakening of the immune system.

People who are in close, prolonged and repeated contact with a person who is tuberculosis and contagious have a higher risk of becoming infected.

Similarly, certain situations favor the transmission of the tubercle bacillus, such as promiscuity in a house that is too small, life in a community, in a group or confined space, and precarious accommodation.

Finally, the more contagious the patient, the greater the risk of contamination from the people around him.

Only 5-10% of those infected develop symptoms of the disease. In 90% of those infected, the disease remains latent.

General signs and symptoms include fever, chills, night sweats, loss of appetite, weight loss, and fatigue.

Pulmonary tuberculosis, which accounts for 90% of tuberculosis cases, is characterized by chest pain and prolonged cough, which is accompanied by sputum.

In some cases, patients may spit blood in small amounts, and in very rare cases, the infection may erode the pulmonary artery.

In 15-20% of cases, tuberculosis can spread outside the lungs and affect various organs such as the skin, pleura, central nervous system, lymphatic system, and bones.


It is extremely difficult to diagnose tuberculosis simply by the signs and symptoms. The basic diagnosis is based on chest radiographs and microscopic observation of sputum samples.

However, culturing this slow-acting bacillus is difficult, and treatment is generally given before confirmatory testing.

Screening for latent tuberculosis can be offered to people at risk, especially people who have been in contact with a patient, immunosuppressed patients, or children under the age of five who live in a high-prevalence area.

Detection of latent tuberculosis allows consideration of its treatment and reduces the risk of developing the active form of the infection.

The doctor will make his diagnosis based on the person’s medical history, evaluation of symptoms, additional tests.The doctor may recommend:

  • X-rays of the lungs: a specialist can study the presence of typical abnormalities of the disease in its pulmonary form, allowing to locate the lesions. However, this test lacks specificity.
  • The use of the skin test or tuberculin test: unfortunately its results are difficult to interpret, a healthy carrier is not detected with certainty, sometimes producing negatives and false positives, which does not allow to distinguish between patients vaccinated with BCG from those infected by M. tuberculosis.
  • This test involves two visits: a first visit to inject the tuberculin into the forearm and a second visit, 48 to 72 hours after the injection, to observe the skin reaction. A negative reaction means that you have never been in contact with the TB germ.
  • The production of interferon gamma detection assays, performed in vitro on a blood sample. However, they are not yet used in current practice although they are more specific.
  • To look for the tuberculosis bacillus, a fasting examination of a sputum is performed, The microbiological diagnosis in a culture of three consecutive days.

In the case of a significant positive tuberculin reaction, always complete the test by a chest radiograph to ensure the absence of pulmonary tuberculosis disease.

If the radiograph is normal, the primary infection is confirmed and preventive treatment may be necessary.

In rare cases where X-rays show signs of TB disease, a more complete review is needed before starting TB treatment.

The blood test is reserved for special situations, such as contact with contagious tuberculosis, medical examination of foreign applicants for immigration.

Like the skin test, the blood test aims to diagnose the primary TB infection with the advantage of avoiding a second visit to read the results.

However, its advantages in relation to its limitations and its cost reserve the use to the particular situations listed above.

In the context of the examination, the chest x-ray can diagnose pulmonary tuberculosis at an early stage even before the person shows signs (cough, fever) or is contagious.

However, it is not systematic and is performed in addition to the skin test or blood test, especially in case of positivity of the same.

Prevention and vaccine

Tuberculosis prevention and control efforts are based primarily on childhood immunization, as well as the detection and appropriate treatment of active cases. The only vaccine available is BCG (Bacillus Calmette-Guerin).

This vaccine was developed in the early 20th century by two French researchers, Albert Calmette and Camille Guérin, by attenuating the bovine tuberculosis germ (M. bovis).

In children, it reduces the risk of contracting the infection by 20% and the risk of latent infection evolving into an active disease by 60%.

To prevent transmission of Koch’s bacillus, contact with infected people should be avoided.

This presupposes the earliest possible diagnosis of the infection and therapeutic isolation of the patient during the contagious phase.

In the hospital, various prophylactic measures are applied: use of the mask (patient, staff, visitors), aeration and exposure of the room to daylight, ultraviolet radiation to which the bacillus is sensitive.

85% of deaths attributable to tuberculosis affect the population of adolescents and young adults.

This is the reason why many teams of researchers are working on the development of new vaccines: 16 of them are being clinically evaluated and many more in earlier stages of development.

Treatment of tuberculosis

Tuberculosis can now be treated and cured.

Treatment is based on combinations of antibiotics given for at least 6 months, sometimes longer.

Generally, it involves four different antibiotics that need to be taken every day for two months, then two antibiotics that need to be taken every day for four months.

Compliance with the protocol is absolutely necessary, otherwise you may develop drug resistance.

Some strains of tuberculosis are now resistant to one or more antibiotics.

More and more multi-drug resistant strains are becoming insensitive to various drugs, including at least the two most effective (isoniazid and rifampin) and second-line antibiotics (fluoroquinolones and injectable tuberculosis).

Although cases of resistant tuberculosis are detected in all countries, more than half are found in India, China and Russia.

It is possible to treat multidrug-resistant tuberculosis, but the treatment is long (at least two years), the price is high (one hundred times the cost of a normal treatment) and the side effects are more marked for the patient. Therefore, convincing patients not to drop out is challenging.

The unusual chemical composition and structure of the cell wall of mycobacteria greatly inhibits the efficacy of many antibiotics.

Treatment in latent form generally uses a single antibiotic, while active tuberculosis is best treated with a combination of several antibiotics.