Causes and Risk Factors

The main cause of Tuberculosis is the passing on of infected droplets. This could be done when someone infected with TB coughs, sneezes, or talks.
When this occurs tiny infected droplets of saliva or mucus that contain the TB bacteria are expelled into the air, which could be inhaled by another person. However prolonged contact is usually needed to become infected.

Coughing image is courtesy of www.flickr.com/photos/changturtle/64548757/ under a creative commons licence. 

The main Risk factors for TB are:

HIV Infection - HIV weakens the immune system which makes it difficult for the body to fight the TB bacteria. Therefore people with HIV are more likely to develop the active form of the disease than people who are not HIV-positive. Tuberculosis is one of the main causes of death among people with AIDS. This is because TB can increase the rate at which the AIDS virus replicates as well as HIV/AIDS patients being more susceptible to TB.

Crowded living conditions - Tuberculosis spreads most easily in crowded, cramped and poorly ventilated areas. This means that people who are in prisons, homeless shelters centres are more susceptible to TB then people who are not associated with these places. TB can also affect nursing homes quite drastically because the elderly normally have a weakened immune system due to illness or aging.

Poverty – People who live in poverty are more likely to have TB because they are least likely to receive medical attention. These people often have to move countries due to their domestic unstable political situations and rarely complete their treatment, if they are lucky enough to be treated. So the medical care is wasted and it often leads to drug-resistant forms of the disease developing in these unfortunate people.

Increase in drug-resistant strains of TB - For each major anti-TB drug, there is a TB bacteria strain that resists its effects. There are even strains that are resistant to at least two anti-TB drugs which is highly dangerous. This condition is called multidrug-resistant TB (MDR-TB). People who have not been treated for MDR-TB are very contagious and can easily spread the disease to other people.

Other risk factors for TB are:

• Other diseases that weaken the immune system 
• Health care workers e.g Doctors or Nurses
• Alcoholism