How can TB be transmitted?

Answer 1

TB is transmitted by the inhalation of airborne organisms. Infectious particles are generated when individuals with pulmonary TB, (e.g., individuals with infection involving lung tissues, respiratory airways, or larynx), cough, sneeze, or speak. Procedures, such as cough induction or bronchoscopy, are associated with an increased generation of infectious, aerosolized particles. Once infectious particles are aerosolized, they are spread throughout a room or building by air currents and can be inhaled by another individual. Initially, the particles are sufficiently large that they can be trapped by the respiratory system of the person inhaling them. As the exhaled particles remain airborne they become dehydrated and decrease until they are one to five microns in size. Particles of this size are called droplet nuclei. These droplet nuclei can avoid the defence system of the upper airway and bronchi and can reach the alveoli where infection can occur.

TB transmission is unlikely to occur from individuals with extrapulmonary TB because infectious particles are usually not aerosolized. Aerosolization may, however, occur in selected laboratory and autopsy procedures or during certain activities, such as the irrigation of TB-infected wounds. Rarely has transmission been reported after injection or direct inoculation of infectious material. Tubercle bacilli on fomites (e.g., linen, furniture, books, and floors) are not infectious and are not a significant infection hazard.

Most people are unaware that they have become infected with TB. They are not ill and have no symptoms of illness because their immune system prevents the development of active TB. A positive tuberculin skin test (TST) may be the only indication that someone has "inactive" TB. People with a positive TST may revert to a negative TST over time, suggesting waning immunity (31) .

Approximately 10% of all individuals infected with M. tuberculosis develop active disease (TB) sometime during their life. The risk of developing active TB is greatest in the first 2 years after initial infection. Re-infection can occur, although this is uncommon (32-34) .


Risk of Transmission
The risk of transmission of TB from one individual to another is dependent upon the following: 1) the patient with active infection, 2) the environment, and 3) the susceptibility of the exposed person.

The patient with active infection

Factors related to the patient that enhance transmission and determine the patient's level of infectivity include, (in decreasing order of importance) the following:

* disease involving the lungs, airways, or larynx (e.g., pulmonary rather than extrapulmonary TB);

* presence of AFB on microscopic direct smear examination of the sputum [see Section IV.D.4] (patients who have a negative AFB sputum smear and who have a positive culture are less contagious, but may transmit infection (35) );

* presence of cavitation, extensive disease, or pneumonic infiltrates on chest radiograph of a patient with pulmonary TB;

* undergoing a procedure that can induce coughing or cause aerosolization of tubercle bacilli (e.g., sputum induction, bronchoscopy) in a patient with pulmonary TB; and

* presence of cough, sneeze, or other forceful expiratory manoeuvre in a patient with pulmonary TB.

Children have generally been considered to have a low risk of transmitting TB. They usually develop non-cavitary TB and frequently do not have a productive cough. However, children with TB have infected other individuals (35) .

The environment

Environmental factors that may enhance the likelihood of transmission (36) include the following:

* presence of someone with active TB who is not on effective therapy (undiagnosed, untreated, non-compliance with treatment, unrecognized drug resistance);

* exposure of susceptible individuals to an infectious person in a relatively small enclosed space;

* inadequate ventilation that results in either insufficient dilution or removal of infectious droplet nuclei;

* re-circulation of air containing infectious droplet nuclei; and

* · duration of exposure.The susceptibility of the exposed person

Some individuals are more susceptible to becoming infected with TB than others. HIV-infected individuals may have increased susceptibility (4) . Individuals with previous TB infection or who received a BCG vaccine are considered less susceptible. The effectiveness of BCG vaccination in adults, however, remains controversial. Meta analysis suggested that BCG is 50% effective in preventing the development of active disease in adults (37) .

Answer 2

It is transmited when someone has the active tuberculosis disease meaning that they can spread it to others. It is spread by air--so once the person breaths, talks, sings, yawns anything that has to do with the mouth, and then you breath in the bacteria into your lungs.

If your have a good immune system you will develope TB latency inactive form and that means your body has stopped the TB from spreading, but it cannot kill it. If later in life you get sick, get HIV/AID or something that weakens your immune system you could get TB active form (disease).

Of the people that have the TB inactive form 10% develop the active TB disease and of those that have the active disease 50% or more die.

Example:
200 people have TB inactive form
20 develop active TB disease
of the 20, 10 or more die.

You can check on www.wikipedia.com (search for tuberculosis) for more information

Answer 3

coughing. Its transmitted through droplets. Those with TB in a hospital are usually isolated and all medical staff wear masks and smocks. Droplets can travel up to 5 feet from the cougher so I'm a little neurotic about people coughing around me.

Answer 4

Much the same way a cold can be transmitted. It can be airborne (through a cough) or through tiny germs left on surfaces.

Answer 5

Tuberculosis is spread through air droplets which are expelled when persons with infectious TB disease cough, sneeze, speak, or sing. Close contacts (persons with prolonged, frequent, or intense contact) are at highest risk of becoming infected (22% infection rate). Others at risk include foreign-born from areas where TB is common, residents and employees of high-risk congregate settings, health care workers who serve high-risk clients, medically underserved, low-income populations, high-risk racial or ethnic minority populations, children exposed to adults in high-risk categories, and persons who inject illicit drugs. The tuberculosis germ is carried on droplets in the air, and can enter the body through the airway. A person with active pulmonary tuberculosis can spread the disease by coughing or sneezing. The process of catching tuberculosis involves two stages: first, a person has to become infected; second, the infection has to progress to disease. To become infected, a person has to come in close contact with another person having active tuberculosis. In other words, the person has to breathe the same air in which the person with active disease coughs or sneezes.

Transmission occurs only from persons with active TB disease (not latent TB infection). A person has to come in contact with someone who has active TB disease with TB germs present in the sputum. The likelihood of this happening also depends on the time spent in close contact with the person with active disease. The process of infection progresses to disease in about ten percent of those infected, and it can happen any time during the remainder of their lives. Although the chance of progression to disease diminishes with the passage of time, tuberculosis can develop more easily if the immune system weakens, as happens with malnutrition, AIDS, diabetes, cancer, or treatment with immunosuppressant drugs. In people with both HIV and TB infection, as many as eight percent can develop TB each year. In the United States, about one person in every 5,500 is diagnosed as infected with tuberculosis.

Answer 6

Any kind of contact with the person even their cough can affect you that's why they are isolated in the hospital and everyone talks to them through masks