To say that you are infected doesn't necessarily mean that you have active disease. You could harbor the causitive pathogen Mycobacteria tuberculosis in your body but not show signs and symptoms of the disease. When this is the case you are considered a carrier.
On the other hand, if you had the mycobacterium in your sputum a screening test used derived from a sputum specimen called sputum for AFB (acid fast bacillus) named after the lab test used called acid fast stain (a type of staining procedure in the lab) could show the organism in the sputum within a couple of days after you were initially exposed to and contracted the microbe. A sputum for AFB test does not mean you have active TB it is an initial screening test. The sputum sample has to be cultured in the microbiology lab.
People exposed to the microbe may or may not actually get the disease and most do not. Many factors determine whether or not you will get active disease, primarily the health of your immune system.
A diagnosis of TB is only made when the persons chest x-ray shows characteristic lesions. However, it may take months for you to have a positive chest x-ray. The diagnosis may be R/O TB, rule out TB. If you are suspected of having TB by showing clinical signs and symptoms like fever, chronic cough, night sweats coupled with either a positive sputum AFB or positive PPD (skin test), the treatment is the same regardless. Note that a positive PPD alone does not mean you have TB.
There are two types of tuberculosis: latent TB and active TB. When a person has latent TB it means that they have been infected with TB but the bacteria are inactive within the body. This kind of TB is not contagious. When a person has active TB they actually become ill and they are also contagious.
Time varies from person to person as far as showing signs of infection. For example, a person can have latent TB for many years and suddenly become ill with active TB because the bacteria has reactivated. Some people may show symptoms of infection fairly quickly.
Skin tests are usually performed to determine if a person has TB. A substance is inserted in the forearm, just under the skin. Within two to three days, a medical professional will look at the injection site to determine if a reaction has taken place. If the area around the site is red or swollen, further testing will be performed.
There are two different forms of tuberculosis: infection and disease. Those people who are infected with the disease neither have symptoms nor can they spread it to others. Those with the disease on the other hand do have symptoms, and can spread it to others. People who are infected, and do not have symptoms can take medication to avoid developing the disease. Infected persons carry the live bacteria; however, the bacteria remains inactive so long the body's immune system is able to stop the bacteria from multiplying. TB only develops in a person who is infected if the body's immune system is unable to stop the bacteria from multiplying. There is no specified duration of time between being infected, and developing the disease as it depends on a great many factors. Some people may never develop it, and others may shortly after.