Tuberculosis has been called the white death, a name that evokes the pale, wasting appearance of those it consumed, and for centuries it was the single greatest killer of humanity. In the 1800s, this disease was responsible for an estimated quarter of all deaths in Europe, a mortality rate so high that it shaped the very fabric of society. It was known as consumption, a term derived from the Latin word for 'to take up from under,' describing how the illness seemed to consume the life from its victims. Hippocrates, writing around 400 BCE, described phthisis as a disease of dry seasons, and skeletal remains from prehistoric humans dating back to 4000 BC show evidence of the disease. The bacterium itself, Mycobacterium tuberculosis, is a small, aerobic, nonmotile bacillus that divides every 16 to 20 hours, a slow pace compared to other bacteria that divide in less than an hour. Despite this slow growth, it has survived in human hosts for tens of thousands of years, with genetic studies suggesting its presence in Southern America from about AD 140 and in Egyptian mummies from 3000 to 2400 BC. The disease's ability to persist in the body for decades, often without symptoms, has made it a ghostly presence in human history, waiting for the moment when the immune system weakens to unleash its full force.
The Discovery of the Bacillus
For centuries, the cause of consumption remained a mystery, with theories ranging from bad air to hereditary weakness, until the 19th century when science began to peel back the layers of the disease. In 1865, Jean Antoine Villemin demonstrated that tuberculosis could be transmitted via inoculation from humans to animals, proving it was contagious, a finding confirmed in 1867 and 1868 by John Burdon-Sanderson. The true breakthrough came on the 24th of March 1882, when Robert Koch identified and described the bacillus causing tuberculosis, M. tuberculosis, a discovery for which he was awarded the Nobel Prize in Physiology or Medicine in 1905. Koch's announcement of a glycerine extract of the tubercle bacilli as a remedy, called tuberculin, in 1890 was a failure as a cure, but it was later successfully adapted as a screening test for the presence of pre-symptomatic tuberculosis. World Tuberculosis Day is marked on the 24th of March each year, the anniversary of Koch's original scientific announcement. Before this discovery, the disease was so feared that in 1815, one in four deaths in England was due to consumption, and by 1918, TB still caused one in six deaths in France. The identification of the bacterium changed the course of history, turning a mysterious wasting disease into a specific target for medical intervention.
Sanatoria and the Fight for Air
Before antibiotics could cure the disease, the world turned to the environment, seeking cures in the cold air of caves and the isolation of sanatoria. Between 1838 and 1845, John Croghan, the owner of Mammoth Cave in Kentucky from 1839 onwards, brought a number of people with tuberculosis into the cave in the hope of curing the disease with the constant temperature and purity of the cave air; each died within a year. Hermann Brehmer opened the first TB sanatorium in 1859 in Görbersdorf, now Sokołowsko, in Silesia, creating a model of care that would spread across the globe. After TB was determined to be contagious, in the 1880s, it was put on a notifiable-disease list in Britain, and campaigns started to stop people from spitting in public places. The infected poor were encouraged to enter sanatoria that resembled prisons, while those of the middle and upper classes received excellent care and constant medical attention. Whatever the benefits of the fresh air and labor in the sanatoria, even under the best conditions, 50% of those who entered died within five years, as recorded in 1916. The sanatorium era was a time of desperate hope, where the very act of breathing clean air was seen as a lifeline, and the disease was treated as a moral failing as much as a medical one.
The true turning point in the battle against tuberculosis arrived in 1946 with the development of the antibiotic streptomycin, which made effective treatment and cure of TB a reality. Prior to the introduction of this medication, the only treatment was surgical intervention, including the pneumothorax technique, which involved collapsing an infected lung to rest it and to allow tuberculous lesions to heal. By the 1950s, mortality in Europe had decreased about 90%, a dramatic decline driven by improvements in sanitation, vaccination, and other public-health measures that began significantly reducing rates of tuberculosis even before the arrival of streptomycin and other antibiotics. The BCG vaccine, developed by Albert Calmette and Camille Guérin in 1906 using attenuated bovine-strain tuberculosis, was first used on humans in 1921 in France, but achieved widespread acceptance in the US, Great Britain, and Germany only after World War II. The introduction of first-line drugs like Isoniazid, Rifampicin, Pyrazinamide, and Ethambutol created a regimen known as HRZE, which could be taken over a period of four or six months to cure drug-susceptible TB. This era marked the transition from a disease of inevitable death to one of manageable treatment, though the victory was not yet complete.
The Rise of Resistance
Just as the world celebrated the triumph of antibiotics, the bacteria began to fight back, developing resistance to the very drugs designed to kill them. A few years after the first antibiotic treatment for TB in 1943, some strains of the TB bacteria developed resistance to the standard drugs, including streptomycin, para-aminosalicylic acid, and isoniazid. Between 1970 and 1990, there were numerous outbreaks of drug-resistant tuberculosis involving strains resistant to two or more drugs, known as multi-drug resistant TB or MDR-TB. The resurgence of tuberculosis, caused in part by drug resistance and in part by the HIV pandemic, resulted in the declaration of a global health emergency by the World Health Organization in 1993. Drug resistance to TB can come in two forms: primary, caused by person-to-person transmission of drug-resistant TB bacteria, and secondary, which develops during TB treatment due to inadequate treatment or non-compliance. Extensively drug-resistant tuberculosis, or XDR-TB, is resistant to rifampicin and isoniazid, and is also resistant to at least one fluoroquinolone and to at least one other Group A drug. The treatment of MDR-TB requires second-line drugs that are less effective, more toxic, and more expensive, with regimens running for up to two years compared to the six months of first-line drug treatment. In the UK in 2013, the cost of treating MDR-TB was estimated to be more than 10 times greater than standard TB treatment, ranging from £50,000 to £70,000 per case.
The Silent Carrier
The majority of individuals with TB infection show no symptoms, a state known as inactive or latent tuberculosis, which is not contagious but can lie dormant for decades. Without treatment, an estimated 5% to 15% of cases will progress into active TB during the person's lifetime, often many years after the initial infection. The bacterium is able to subvert the normal process of the immune system by inhibiting the development of the phagosome and preventing it from fusing with the lysosome, allowing it to survive and replicate within the macrophage. In the next stage of infection, macrophages, epithelioid cells, lymphocytes, and fibroblasts aggregate to form a granuloma, which surrounds and isolates the infected macrophages, containing the infection but not destroying the bacilli. This granuloma contains necrotic tissue at its center, appearing as a small white nodule, also known as a tubercle, from which the disease derives its name. If the immune system is unable to control the infection, the disease can progress to active TB, which can cause significant damage to the lungs and other organs. People with HIV are 16 times more likely to fall ill with TB than people without HIV, and TB is the leading cause of death among people with HIV, with the risk of reactivation increasing to 10% per year in coinfected individuals.
The Global Burden
Tuberculosis remains the leading cause of death from an infectious disease, with an estimated 10.7 million people newly infected in 2024 and 1.23 million deaths, making it a persistent threat to global health. Approximately 87% of new TB cases occur in the 30 high TB burden countries, with more than two-thirds of the global burden occurring in Bangladesh, China, the Democratic Republic of the Congo, India, Indonesia, Nigeria, Pakistan, and the Philippines. India alone is estimated to have 40% of its population carry tuberculosis infection, attributed to widespread poverty, malnutrition, overcrowding, and poor hygiene. The disease disproportionately affects low-income populations and countries, with factors like poverty, inadequate living conditions, and poor nutrition contributing to higher TB prevalence and incidence in these settings. In Lesotho, there are an estimated 664 new infections per 100,000 population in 2023, one of the highest TB incidence rates globally, largely due to the extremely high prevalence of HIV in the adult population. The incidence of TB varies with age, occurring mainly in adults 15 years and older, with men more likely to be infected than women, and in countries with a low burden of TB, incidence rates among those 65 and older are consistently higher than in other age groups.