Tuberculosis

• 1. Introduction

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  Tuberculosis once carried the name the white death, and in 19th-century New England, its slow march through families was blamed on vampires. When one family member died, the others would fade, and people believed the dead were draining the life from the living. The disease has been called consumption, phthisis, and the great white plague. In the 1800s it was responsible for an estimated quarter of all deaths in Europe. Today it remains the leading cause of death from a single infectious agent worldwide. In 2024, it reached an estimated 10.7 million people and caused 1.23 million deaths. How does a single rod-shaped bacterium hide inside the body's own immune cells for a lifetime? Why did a disease once tied to poetry and genius become a marker of poverty? And why, after the discovery of a cure, does it still kill more than a million people a year?

• 2. A Bacterium That Hides

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  Mycobacterium tuberculosis divides only every 16 to 20 hours, painfully slow for a bacterium, since most others split in under an hour. Its cell envelope is rich in lipids, and that high lipid content forms a robust barrier that contributes to drug resistance. When a Gram stain is applied, the bacterium either stains very weakly or refuses to hold the dye at all. It can withstand weak disinfectants and survive in a dry state for weeks. The infection begins when an inhaled bacterium reaches the alveoli of the lungs and meets an alveolar macrophage, an immune cell meant to destroy it. The macrophage stretches around the invader and swallows it into a compartment called a phagosome, which normally fuses with a lysosome full of digestive enzymes. M. tuberculosis subverts this, blocking that fusion so it can survive and replicate inside the very cell sent to kill it. Eventually it destroys the macrophage and releases new bacteria to spread. The body's answer is the granuloma, a wall of macrophages, epithelioid cells, lymphocytes, and fibroblasts that surrounds the infection. At its center sits necrotic tissue, a small white nodule called a tubercle, and it is from this nodule that the disease takes its name.

• 3. The Sleeping Infection

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  Roughly one-quarter of the world's population, about 2 billion people, carry latent tuberculosis. Most infections cause no symptoms at all, and between 90 and 95 percent of infections stay asymptomatic. A latent infection is not contagious, and people who carry it do not spread the disease. Without treatment, an estimated 5 to 15 percent of cases progress to active disease over a lifetime, often many years after the original infection. The risk rises sharply when the immune system weakens. Among people coinfected with HIV, the chance of reactivation climbs to 10 percent per year. When the infection does activate, it most often returns to the lungs, in about 90 percent of cases, bringing chest pain, a prolonged cough that may turn bloody, fever, wasting, and malaise. In rare cases the infection erodes into the pulmonary artery, forming a Rasmussen aneurysm and causing massive bleeding. In 15 to 20 percent of active cases, the disease moves beyond the lungs entirely. It can reach the pleura, the central nervous system, the lymphatic system, the genitourinary tract, and the bones and joints, as in Pott disease of the spine. Urogenital tuberculosis can appear decades after lung symptoms have resolved, often in patients who show no pulmonary signs at all.

• 4. Naming The Captain Of Death

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  In John Bunyan's The Life and Death of Mr Badman, the author calls consumption the captain of all these men of death. The word consumption comes from the Latin con, meaning completely, and sumere, to take up from under, and it was the most common English name for the disease in the nineteenth century. In ancient Greek, phthisis translates to decay or wasting disease, and around 460 BCE Hippocrates described it as a disease of dry seasons. The Latin tabes carried a similar meaning. The disease was so familiar across history that it accumulated names in age after age, from the great white plague to the white death. The path to a single scientific identity was slow. Richard Morton established the pulmonary form tied to tubercles as a pathology in 1689, yet the variety of symptoms meant TB was not recognized as one disease until the 1820s. In 1720, Benjamin Marten conjectured that consumption was caused by microbes spread by people living close together. In 1819, Rene Laennec claimed tubercles were the cause of pulmonary tuberculosis. The name tuberculosis itself was first published in 1832, by J. L. Schoenlein.

• 5. The Romantic Disease

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  Tuberculosis was once called the romantic disease, and for centuries it was tied to poetic and artistic gifts. The poets John Keats, Percy Bysshe Shelley, and Edgar Allan Poe carried its mark, alongside the composer Frederic Chopin and the playwright Anton Chekhov. The novelists Franz Kafka, Charlotte Bronte, Fyodor Dostoevsky, Thomas Mann, George Orwell, and Robert Louis Stevenson, and artists including Edvard Munch and Amedeo Modigliani, either had the disease or lived among those who did. A widespread belief held that the illness assisted artistic talent. The proposed mechanisms were strange: the slight fever and toxaemia were said to help sufferers see life more clearly and act decisively. The theme threaded through the arts themselves. Thomas Mann set The Magic Mountain in a sanatorium. Van Morrison wrote the song T.B. Sheets. Puccini's La boheme and Verdi's La Traviata carried it into opera, Munch painted his ill sister, and the 1945 film The Bells of St. Mary's starred Ingrid Bergman as a nun with tuberculosis.

• 6. Caves, Sanatoria, And The Cure

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  Between 1838 and 1845, John Croghan brought many people with tuberculosis into Mammoth Cave in Kentucky, hoping the constant temperature and pure air would cure them. Each of them died within a year. The sanatorium era began in 1859, when Hermann Brehmer opened the first such institution in Goerbersdorf in Silesia. After the disease was found to be contagious in the 1880s, the infected poor were pressured into sanatoria that resembled prisons, while the middle and upper classes received excellent care. Even under the best conditions, around 1916, half of those who entered died within five years. Robert Koch identified and described the bacillus on the 24th of March 1882, and in 1905 he received the Nobel Prize in Physiology or Medicine for the discovery. World Tuberculosis Day is still marked on the 24th of March, the anniversary of his announcement. In 1890 Koch offered a glycerine extract of the bacilli as a remedy he called tuberculin, which proved ineffective but was later adapted into a screening test. Real immunization came in 1906, when Albert Calmette and Camille Guerin succeeded using an attenuated bovine strain, producing the BCG vaccine first used on humans in 1921. The true turning point arrived in 1946, when the antibiotic streptomycin made cure a reality. Before it, the only treatment was surgery, including the pneumothorax technique of collapsing an infected lung to rest it. By the 1950s, mortality in Europe had decreased by about 90 percent.

• 7. When The Drugs Stop Working

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  A few years after the first antibiotic treatment for TB in 1943, some strains developed resistance to the standard drugs: streptomycin, para-aminosalicylic acid, and isoniazid. Between 1970 and 1990, outbreaks of multi-drug resistant TB emerged, resistant to two or more drugs at once. This resurgence, driven by drug resistance and the HIV pandemic, led the World Health Organization to declare a global health emergency in 1993. Resistance now has formal tiers. Multi-drug resistant tuberculosis is defined by resistance to rifampicin and isoniazid, the two most effective first-line drugs. Extensively drug-resistant tuberculosis adds resistance to a fluoroquinolone and another Group A drug such as bedaquiline or linezolid. A further category, totally drug resistant tuberculosis, has no accepted definition but was first observed in Italy in 2003. The cost is staggering. In the UK in 2013, standard TB treatment was estimated at 5,000 pounds, while treating MDR-TB ran from 50,000 to 70,000 pounds per case. Treatment regimens once stretched between 18 and 24 months, far longer than the six months for first-line drugs. The WHO now recommends shorter oral regimens, including the six-month BPaLM combination of bedaquiline, pretomanid, linezolid, and moxifloxacin.

• 8. An Unequal Burden

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  Approximately 87 percent of new TB cases occur in just 30 high-burden countries, with more than two-thirds concentrated in Bangladesh, China, the Democratic Republic of the Congo, India, Indonesia, Nigeria, Pakistan, and the Philippines. In India, an estimated 40 percent of the population carries the infection, though incidence fell from nearly 300 per 100,000 in 2010 to 200 in 2023. Lesotho still bears one of the highest rates on earth, with an estimated 664 new infections per 100,000 in 2023, tied to an adult HIV prevalence around 23 percent. The strongest thread running through these numbers is poverty. People of low socioeconomic status are more likely to contract TB, facing malnutrition, HIV co-infection, crowded and poorly ventilated spaces, and limited access to care. HIV remains the single most important risk factor, and people living with HIV are estimated 12 times more likely to develop TB. Indigenous peoples are disproportionately affected. Australian Indigenous populations face rates more than four times those of non-Indigenous Australian-born people, and in 2023 the rate among First Nations in Canada was over three times the overall national rate. Stigma deepens the toll, with between 42 and 82 percent of people with TB reporting that they have experienced it. In India, a diagnosis can cost someone their job or their chance to marry, and that silence lets the disease keep spreading. The path forward runs through the End TB strategy, which aims to cut TB deaths by 90 percent and incidence by 80 percent by 2030, a target that depends on faster tests, shorter treatments, and a vaccine better than the century-old BCG.