TB is caused by a bacterium (Mycobacterium tuberculosis) that is spread through the air when infected people cough or sneeze.

The disease most often affects the lungs but it can infect any part of the body, including the bones and the nervous system.
Most people who are exposed to TB never develop symptoms, since the bacteria can live in an inactive form in the body, but if the immune system weakens, such as in malnourished people, people with HIV or the elderly, TB bacteria can become active.

Five to 15 per cent of people infected with TB will develop active TB and become contagious at some point in their lives.

Symptoms include a persistent cough, fever, weight loss, chest pain and breathlessness in the lead up to death. TB incidence is much higher and is a leading cause of death among people with HIV.

The most widely-used test for diagnosing active TB in developing countries relies on examining a patient’s phlegm under a microscope. This method, developed nearly 140 years ago, detects less than half of all TB cases and largely fails to detect the disease in children and people co-infected with HIV – who usually can’t produce the sputum needed – and those with drug-resistant forms of TB. A diagnostic test, Xpert MTB/RIF, was introduced and we use it in many of our projects, but it can't be used in resource-limited settings.

A course of treatment for uncomplicated TB takes a minimum of six months. Drug-resistant TB (DR-TB) treatment requires taking a cocktail of drugs and can take two years or more, but trials are ongoing to treat it in six to nine months. It is vital that a patient completes their entire course of treatment, even when they start to feel better; incomplete treatment can lead to drug resistance developing. Decentralising treatment by having people cared for at home can help them adhere to treatment and overcome any obstacles they may face.