A quarter of humanity carries latent tuberculosis
Mycobacterium tuberculosis still tops single-agent infectious deaths worldwide. Roughly two billion people harbor latent infection; in 2024 about 10.7 million fell ill and 1.23 million died. Most carriers never cough, and they cannot spread the bug until immunity finally slips.
TB usually starts in the lungs after airborne droplets from an active case, then can seed other organs. Latent infection shows no symptoms and is not contagious; an estimated 5–15% of untreated latent cases become active over a lifetime, more often when immunity is weak. Active disease classically brings chronic cough with bloody sputum, fever, night sweats, and weight loss. About 90% of active cases are pulmonary. Tests include interferon-gamma release assays, tuberculin skin tests, and nucleic acid amplification; WHO favors rapid Xpert MTB/RIF to confirm TB and rifampicin resistance together. Prevention rests on screening contacts, early treatment, and BCG vaccination.
Ancient spines and mummies show the disease millennia back; genetic traces appear in South America by about AD 140. In nineteenth-century Europe “consumption” caused nearly a quarter of deaths—one in four English deaths in 1815, still one in six in France in 1918. Robert Koch identified M. tuberculosis on 24 March 1882 (Nobel 1905); World TB Day marks that date. Calmette and Guérin attenuated a bovine strain into BCG, first given to humans in France in 1921. Streptomycin in 1946 made cure realistic; European mortality had already fallen about 90% by the 1950s through sanitation and public health, yet resistance emerged within years of the first antibiotics.
WHO declared a global TB emergency in 1993 amid MDR-TB and HIV-linked resurgence. MDR-TB resists rifampicin and isoniazid; XDR-TB adds resistance to a fluoroquinolone and bedaquiline or linezolid. In 2023 about 3.2% of new cases were RR/MDR-TB (down from 4.0% in 2015); among previously treated patients the share fell from 25% to 16%. Second-line regimens can last two years versus six months for standard therapy—and cost far more: UK 2013 estimates put ordinary treatment near £5,000 and MDR care at £50,000–£70,000. Even after cure, lung scarring can leave chronic cough and breathlessness.
Source: Tuberculosis
