Pulmonary tuberculosis : a student infected can infect 10 to 15 people
Published the 07.12.2017 at 11: 40 am
Tuberculosis of the respiratory was diagnosed in a student, Besançon, france, Tuesday, December 5, according to the Regional Agency of health (ARS). It is a pulmonary form which is so contagious to the entourage of the patient, especially in cases of coughs. The ARS will be to propose a tuberculin skin test and a review of the lung to all the people who have been in contact recently with the student. The risk of contamination increases with the duration of contact with the student and his proximity, this are the close contacts that are involved. The answer to Why Doctor the main questions that you ask
What is tuberculosis ?
Tuberculosis is an infection due to the bacillus of Koch (Mycobacterium tuberculosis) that affects in priority the lungs, but not only. This agent blight is transmitted by the airborne route via droplets contaminated by the bacteria, which are suspended in the air expired by the sick, especially when coughing.
The movement of people (travellers, refugees) have largely contributed in recent years to the spread of the disease in the world. In western countries, tuberculosis is especially common among homeless people and the immunocompromised (AIDS and patients under immunosuppressive regimens).
How do you get the pulmonary tuberculosis ?
The reservoir of Mycobacterium tuberculosis is the man, reached by an active form of tuberculosis. Tuberculosis is spread mainly by the airway : a cough, a sneeze, a spitting, or even a simple discussion too close to his interlocutor, projecting the tubercle bacilli into the ambient air. The person who inhales these droplets in suspension in turn becomes infected.
The lung is the main entrance door of the germ in latent tb, and the primary localization of infection in tuberculosis disease. In the case of a strong infection, the bacteria can cause defenses ganglion and spread through the body via the lymphatic system and blood. It is estimated that an infected and not treated, can infect 10 to 15 other people in the space of a year.
Some strains are close relatives, such as Mycobacterium bovis, can be found as a reservoir in domestic animals and therefore be transmitted through food.
When one is sick is it contagious ?
A patient with pulmonary tuberculosis is contagious if we found the bacillus in the analysis of his sputum. The greater the number of bacilli is high, the more the patient is contagious. In general, a person with tb, extra-pulmonary, without any lung involvement, is not contagious.
Any sick person who is contagious should wear a mask to avoid contaminating those around them, and especially avoid contact of the delicate persons : children under 15 years of age, the elderly, immunocompromised individuals and pregnant women.
As the antibiotic treatment for tb, the number of bacilli thrown into the saliva by the patient decreases, and the risk of contagion too. The risk of contagion decreases so quickly after the start of treatment and is void in general after 3 weeks of treatment.
How to declare the tb ?
In 10% of infected people, the bacterium is not sufficiently controlled by the immune system and these people develop a form of tuberculosis, the so-called “active” which will cause disease and complications.
The organs most often affected by tb infection are the lungs (more than two-thirds of the cases) : this is called ” pulmonary tuberculosis “, which is also the contagious form of the disease. Tuberculosis can also infect the lymph nodes, the skin, the kidneys, the brain (” meningitis “), the bones, the intestines : it is the ” tb extra-pulmonary “, which is the non-contagious form.
All the people infected by the Koch bacillus does not develop, therefore, not the disease, but the bacillus of Koch, which can remain in the organization in the state “dormant” for years, can also wake up to develop the infection on the occasion of the weakened secondary of the immune system of the person with dementia (such as HIV, chemotherapy, immunosuppressive therapy).
What are the signs of pulmonary tuberculosis ?
After the contact with the bacillus of Koch the occurrence of an incubation phase in which the bacteria fight against the immune defences of the infected person to develop. It lasts from one to three months and usually goes unnoticed. One can possibly have a moderate fever (38° C) and feel a little bit of fatigue.
Most often, the pulmonary tb is manifest by signs not very specific, but whose persistence beyond three weeks should give the warning : a persistent cough and unexplained for more than 15 days, a nagging bronchitis, significant weight loss and unexplained, prolonged fever of 37.5°, or 38.5°C, night sweats, extreme tiredness, sputum bloody when coughing (” hemoptysis “), a loss of weight.
It is also possible to observe lesions of the skin quite evocative, what is called an ” erythema nodosum “, which are in the form of inflammatory nodules in red sitting under the skin, in the anterior part of the legs mainly.
For the extrapulmonary forms of tb, the signs are more variable and in connection with the location.
What are the complications of tb ?
Tb infection can be revealed by complications locorégionales or general, which may be early or late.
- The early complications are the prerogative of the people whose defences are down-regulated. They are mainly related to a hypertrophy of the lymph nodes in the chest, ” mediastinal lymphadenopathy “, which are responsible for narrowing of the bronchus by external compression and/or fistulisation. More rarely, one can observe a complication of the canker in the form of a home round, dense, sometimes excavated (” cave “). In some cases, the evolution can be done from the outset in the form of a general release in the bloodstream (” hematogenous “) : the complication most dreaded in this case is the meningitis.
- The complication of late are rarely locorégionales (stenosis, bronchial, bronchiectasis, as hemoptysis by hyper-vascularization systemic sequelae calcified). This is mostly a progression to maturity variable (from several months to several years) to tb disease : pulmonary tuberculosis, tuberculosis of uro-genital tuberculosis, bone, lymph node tuberculosis…
When should it evoke a tb ?
The disease occurs when the bacteria multiplies and different signs are not very specific, then appear (cough, fatigue, weight loss, etc.), associating a variable which complicates the diagnosis.
It is their persistence for more than 3 weeks should alert : fever, shuffling, with night sweats, cough with sputum, sometimes with a few threads of blood, shortness of breath, pain in the chest and sometimes in the joints or back, headaches, fatigue, loss of appetite, weight loss.
How to make the diagnosis of tuberculosis ?
The diagnosis of tb infection is based on the observation of a shift recent of the skin reactions to tuberculin. The tests consist in introducing into the dermis a small amount of tuberculin, which is a product of the lysis of tubercle bacilli (and therefore killed bacteria non-virulent).
The test is most often performed using a ring tb (multi-test), but the reference test is “the intradermo-reaction to the tuberculin’: it consists in the intradermal injection strict of 0.1 ml of tuberculin purified with 10 units. A local inflammatory reaction is observed 48 to 72 h later in case of a positive test (indicating the hypersensitivity cell-mediated). It is of an elevated red of the skin (” blister “) of at least 10 mm (5 mm in case of immunosuppression).
The test may be falsely positive in cases of lesions of scratching or secondary infection or, more simply, as a result of a confusion between a simple local redness (erythema) and a blister. It can be falsely negative early in the disease because there is an interval free of 6 to 8 weeks between the beginning of the infection and the acquisition of the immune response.
The diagnosis of pulmonary tuberculosis is based on the examinations in particular, a chest x-ray and the search for the bacilli of Koch.
The chest x-ray revealed opacities abnormal, in the form of “nodules” or “caves” in the case of tb. An inflammatory syndrome may be present (or absent). A search of the bacilli of Koch, is performed in different samples as a function of the location of the infection : in cases of pulmonary tuberculosis, the sputum that is studied. The research of the bacilli can also be made to other samples : urine, cerebrospinal fluid, puncture of pleura, aspiration of abscesses, etc.). Only the identification of the bacilli is a diagnosis of certainty.
If sputum is spontaneous may not be obtained, two methods are used : the casing gastric done in the morning before sunrise (introduction of a tube into the stomach through the nose or mouth in order to study the bronchial secretions swallowed unconsciously during the night) or fiberoptic endoscopy bronchial aspiration of secretions (examination of the inside of an organ through a fiberscope, a small device flexible consisting of fiber-optic transmitting light and image).
New tests for the immunological diagnosis of tuberculosis are now available. These tests (QuantiFERON-TB and T-SPOT.TB), would be more sensitive than the intradermo-reaction, and they were the fact that the subjects were in contact with tuberculosis, regardless of their ability to form or not of granulomas.