HOW DO YOUCATCH TUBERCULOSIS?When a person who has contagious pul-monary tuberculosis coughs or sneezes,germs are released into the air. Anotherperson can become infected by breathingin these germs. Most people infected withthe germ will not develop the disease. Therisk of developing the disease is greater inclose contacts if their physical resistancehas been weakened by any of the following:

• a serious disease such as diabetes,HIV infection, cancer or a treatmentthat weakens the immune system;

• their lifestyle (alcoholism, drug addic-tion, poor nutrition);

• age: the elderly and young children aremore vulnerable.

WHO IS CONSIDEREDA CLOSE CONTACT?Any person who lives in the same house asa person who has pulmonary tuberculosis.The term may also apply to people outsidethe home who are in frequent or prolongedcontact with the sick person, such co-workers,friends and other family members.

WHAT IS LATENT TUBERCULOSISINFECTION?In this state, the tuberculosis germ isdormant – present in the body but notactive. Latent tuberculosis infectionoccurs after a person’s first contact withthe germ. Mostly, this first contact doesnot lead to any symptoms or clinicalsigns, and 90% of people will not devel-op the disease. Latent infection can bedetected, in the majority of cases, by apositive reaction to a tuberculin skintest. However, latent tuberculosis infec-tion is not contagious.

WHAT IS PULMONARYTUBERCULOSIS?In this state, the tuberculosis germ isactive and causes symptoms such ascoughing, spitting, weight loss, fatigue,fever and sweating. This occurs when aperson infected by the tuberculosis germis unable to fight it. The disease iscaused by the germs multiplying andspreading in the body. The disease usu-ally strikes the lungs but it may alsoaffect other organs such as the lymphglands, kidneys, and bones. When itaffects the lungs, tuberculosis disease isoften contagious.

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TESTING FOR

TUBERCULOSIS:the TST

TUBE

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WHAT ARE THEPOSSIBLE REACTIONS?Between 48 and 72 hours after takingthe test, redness and a small bump mayappear at the injection site. The size of thebump has to be measured by someonewith training.

It is very important that you keep yourappointment for the test results, even ifthere does not appear to be any redness orbump.

A NEGATIVE REACTIONA negative reaction means that you havenever been in contact with the tuberculosisgerm or that your body has lost its abilityto react to the test. If the TST is negative, itwill be repeated in some people because itmay take up to two months after the lastcontact for a positive reaction to appear.

HOW IS THE TUBERCULOSISGERM DETECTED?The tuberculosis germ is detected by atuberculin skin test known as the TSTor Mantoux test. This test is neither atreatment nor a vaccine. It showswhether you have ever been in contactwith the tuberculosis germ, and whetheryou are at risk of developing the diseaselater on.

The TST requires two visits. At the firstvisit, a small quantity of a substancecalled tuberculin is injected into yourskin on the inside of your forearm. Atthe second visit, 48 to 72 hours after thefirst, someone with training reads theresults.

IF YOU HAVE ALREADY HAD A TST,IT IS IMPORTANT TO TELL YOUR DOCTOR,AS YOU MAY NOT NEED ANOTHER ONE.

WHAT PRECAUTIONS SHOULDBE TAKEN AFTER THE TST?• Do not put anything on the injection

site (for example, a sticking plaster oran ointment);

• Do not irritate the injection site (forexample, scratching, rubbing, orwashing with soap).

You can continue your usual activities,and take a bath or shower. If it itches,apply a cold water compress.

A POSITIVE REACTIONA positive reaction means that your bodyhas already encountered the tuberculosisgerm and has developed defence mecha-nisms: this is latent tuberculosis infection.The tuberculosis vaccine (BCG) mayalso cause a positive reaction. You maybe recommended to have more tests,such as a chest X-ray and a medicalexam, to make sure that you do not havepulmonary tuberculosis. Your doctormay also suggest that you start preven-tive treatment. People who have been incontact with a case of tuberculosis arenot contagious and represent no dangerto those close to them.

WHAT IS TUBERCULOSIS?Tuberculosis is an infectious diseasecaused by a germ called Mycobacteriumtuberculosis. It usually develops in the lungsbut it may also affect other organs such asthe lymph glands, kidneys, and bones.To understand tuberculosis and how it isdetected, it is important to know the difference between two conditions: latenttuberculosis infection and pulmonarytuberculosis.