Tuberculosis

Tuberculosis (TB) is a disease that mostly affects the lungs. It’s caused by a bacterium called Mycobacterium Tuberculosis (MTB). Most people that have TB don’t have any symptoms. In this case, it’s called “latent” TB. 10% of latent TB progresses to the active disease, and 50% of people with active TB will die if not treated.

In the 1800s, 25% of all deaths in the world were caused by TB. In 2015, it was only 2.43%.

The most common symptoms of TB are weight loss, fever, night sweats, and coughing up blood. The weight loss is what led many people to call it Consumption in the past.

It’s believed that one in every three people has TB. It’s spread through the air by people that have the active form, through speaking, sneezing, coughing, etc.

We’ve made a lot of progress in this disease, with developed countries now reporting an incidence of only 10%, versus an 80% incidence in developing countries. Mostly, this has been through increased sanitation and other public health measures. Recent discoveries in vaccines and antibiotics have helped a lot.7

Since 2000, the number of deaths each year has decreased.

People with Silicosis are 30 times as likely to contract it as people without. People with Diabetes Mellitus 3 times as likely. Smokers are twice as likely as non-smokers. If you have a compromised immune system (such as with HIV/AIDS), the latent bacterium can quickly overcome your immune system and become active.

Illustration 7: image from Wikipedia showing x-ray of advanced tuberculosis. white arrows mark pulmonary infiltrates (substances denser than air). black arrows mark a cavity where the lung has completely been eaten away

The only vaccine against TB that exists at time of writing is the BCG (first tested on humans in 1921), which reduces the risk of infection by 20%, and reduces the risk of latent turning to active by 60%. Since its introduction, 90% of all children in the world have been vaccinated with it.

The chance of dying from TB in 1995 was 8%. Thanks mostly to the BCG vaccine, the chance 13 years later was 4%. This is most dramatic in countries where the vaccination was strictly enforced. In China, the chance of dying from TB reduced by 80% between 1990 and 2010.

TB these days is mostly a disease that only affects older people, because younger people have been vaccinated against it.