in 1995. in people with smear-positive pulmonary tb (without hiv co-infection), after 5 years without treatment, 50-60% die while 20-25% achieve spontaneous resolution (cure). tb is almost always fatal in those with untreated hiv co-infection and death rates are increased even with antiretroviral treatment of hiv. epidemiology roughly one-quarter of the world's population has been infected with m. tuberculosis, with new infections occurring in about 1% of the population each year. however, most infections with m. tuberculosis do not cause disease, and 90–95% of infections remain asymptomatic. in 2012, an estimated 8.6 million chronic cases were active. in 2010, 8.8 million new cases of tuberculosis were diagnosed, and 1.20–1.45 million deaths occurred (most of these occurring in developing countries). of these, about 0.35 million occur in those also infected with hiv. in 2018, tuberculosis was the leading cause of death worldwide from a single infectious agent. the total number of tuberculosis cases has been decreasing since 2005, while new cases have decreased since 2002. tuberculosis incidence is seasonal, with peaks occurring every spring and summer. the reasons for this are unclear, but may be related to vitamin d deficiency during the winter. there are also studies linking tuberculosis to different weather conditions like low temperature, low humidity and low rainfall. it has been suggested that tuberculosis incidence rates may be connected to climate change. at-risk groups tuberculosis is closely linked to both overcrowding and malnutrition, making it one of the principal diseases of poverty. those at high risk thus include: people who inject illicit drugs, inhabitants and employees of locales where vulnerable people gather (e.g., prisons and homeless shelters), medically underprivileged and resource-poor communities, high-risk ethnic minorities, children in close contact with high-risk category patients, and health-care providers serving these patients. the rate of tuberculosis varies with age. in africa, it primarily affects adolescents and young adults. however, in countries where incidence rates have declined dramatically (such as the united states), tuberculosis is mainly a disease of the elderly and immunocompromised (risk factors are listed above). worldwide, 22 "high-burden" states or countries together experience 80% of cases as well as 83% of deaths. in canada and australia, tuberculosis is many times more common among the indigenous peoples, especially in remote areas. factors contributing to this include higher prevalence of predisposing health conditions and behaviours, and overcrowding and poverty. in some canadian indigenous groups, genetic susceptibility may play a role. socioeconomic status (ses) strongly affects tb risk. people of low ses are both more likely to contract tb and to be more severely affected by the disease. those with low ses are more likely to be affected by risk factors for developing tb (e.g., malnutrition, indoor air pollution, hiv co-infection, etc.), and are additionally more likely to be exposed to crowded and poorly ventilated spaces. inadequate healthcare also means that people with active disease who facilitate spread are not diagnosed and treated promptly; sick people thus remain in the infectious state and (continue to) spread the infection. geographical epidemiology the distribution of tuberculosis is not uniform across the globe; about 80% of the population in many african, caribbean, south asian, and eastern european countries test positive in tuberculin tests, while only 5–10% of the u.s. population test positive. hopes of totally controlling the disease have been dramatically dampened because of many factors, including the difficulty of developing an effective vaccine, the expensive and time-consuming diagnostic process, the necessity of many months of treatment, the increase in hiv-associated tuberculosis, and the emergence of drug-resistant cases in the 1980s. in developed countries, tuberculosis is less common and is found mainly in urban areas. in europe, deaths from tb fell from 500 out of 100,000 in 1850 to 50 out of 100,000 by 1950. improvements in public health were reducing tuberculosis even before the arrival of antibiotics, although the disease remained a significant threat to public health, such that when the medical research council was formed in britain in 1913 its initial focus was tuberculosis research. in 2010, rates per 100,000 people in different areas of the world were: globally 178, africa 332, the americas 36, eastern mediterranean 173, europe 63, southeast asia 278, and western pacific 139. russia russia has achieved particularly dramatic progress with a decline in its tb mortality rate—from 61.9 per 100,000 in 1965 to 2.7 per 100,000 in 1993; however, mortality rate increased to 24 per 100,000 in 2005 and then recoiled to 11 per 100,000 by 2015. china china has achieved particularly dramatic progress, with about an 80% reduction in its tb mortality rate between 1990 and 2010. the number of new cases has declined by 17% between 2004 and 2014. africa in 2007, the country with the highest estimated incidence rate of tb was eswatini, with 1,200 cases per 100,000 people. in 2017, the country with the highest estimated incidence rate as a % of the population was lesotho, with 665 cases per 100,000 people. india as of 2017, india had the largest total incidence, with an estimated 2,740,000 cases. according to the world health organization (who), in 2000–2015, india's estimated mortality rate dropped from 55 to 36 per 100,000 population per year with estimated 480 thousand people died of tb in 2015. in india a major proportion of tuberculosis patients are being treated by private partners and private hospitals. evidence indicates that the tuberculosis national survey does not represent the number of cases that are diagnosed and recorded by private clinics and hospitals in india. north america in the united states, native americans have a fivefold greater mortality from tb, and racial and ethnic minorities accounted for 84% of all reported tb cases. in the united states, the overall tuberculosis case rate was 3 per 100,000 persons in 2017. in canada, tuberculosis is still endemic in some rural areas. western europe in 2017, in the united kingdom, the national average was 9 per 100,000 and the highest incidence rates in western europe were 20 per 100,000 in portugal. number of new cases of tuberculosis per 100,000 people in 2016 tuberculosis deaths per million persons in 2012 tuberculosis deaths by region, 1990 to 2017 history main article: history of tuberculosis egyptian mummy in the british museum – tubercular decay has been found in the spine. tuberculosis has existed since antiquity. the oldest unambiguously detected m. tuberculosis gives evidence of the disease in the remains of bison in wyoming dated to around 17,000 years ago. however, whether tuberculosis originated in bovines, then transferred to humans, or whether both bovine and human tuberculosis diverged from a common ancestor, remains unclear. a comparison of the genes of m. tuberculosis complex (mtbc) in humans to mtbc in animals suggests humans did not acquire mtbc from animals during animal domestication, as researchers previously believed. both strains of the tuberculosis bacteria share a common ancestor, which could have infected humans even before the neolithic revolution. skeletal remains show some prehistoric humans (4000 bc) had tb, and researchers have found tubercular decay in the spines of egyptian mummies dating from 3000 to 2400 bc. genetic studies suggest the presence of tb in the americas from about ad 100. before the industrial revolution, folklore often associated tuberculosis with vampires. when one member of a family died from the disease, the other infected members would lose their health slowly. people believed this was caused by the original person with tb draining the life from the other family members. although richard morton established the pulmonary form associated with tubercles as a pathology in 1689, due to the variety of its symptoms, tb was not identified as a single disease until the 1820s. benjamin marten conjectured in 1720 that consumptions were caused by microbes which were spread by people living close to each other. in 1819, rené laennec claimed that tubercles were the cause of pulmonary tuberculosis. j. l. schönlein first published the name "tuberculosis" (german: tuberkulose) in 1832. 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. in 1865, jean antoine villemin demonstrated that tuberculosis could be transmitted, via inoculation, from humans to animals and among animals. (villemin's findings were confirmed in 1867 and 1868 by john burdon-sanderson.) robert koch discovered the tuberculosis bacillus. robert koch identified and described the bacillus causing tuberculosis, m. tuberculosis, on 24 march 1882. in 1905, he was awarded the nobel prize in physiology or medicine for this discovery. koch did not believe the cattle and human tuberculosis diseases were similar, which delayed the recognition of infected milk as a source of infection. during the first half of the 1900s, the risk of transmission from this source was dramatically reduced after the application of the pasteurization process. koch announced a glycerine extract of the tubercle bacilli as a "remedy" for tuberculosis in 1890, calling it "tuberculin". although it was not effective, it was later successfully adapted as a screening test for the presence of pre-symptomatic tuberculosis. world tuberculosis day is marked on 24 march each year, the anniversary of koch's original scientific announcement. albert calmette and camille guérin achieved the first genuine success in immunization against tuberculosis in 1906, using attenuated bovine-strain tuberculosis. it was called bacille calmette–guérin (bcg). the bcg vaccine 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. tuberculosis caused widespread public concern in the 19th and early 20th centuries as the disease became common among the urban poor. in 1815, one in four deaths in england was due to "consumption". by 1918, tb still caused one in six deaths in france. after tb was determined to be contagious, in the 1880s, it was put on a notifiable-disease list in britain; campaigns started to stop people from spitting in public places, and the infected poor were "encouraged" to enter sanatoria that resembled prisons (the sanatoria for the middle and upper classes offered 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 (c. 1916). when the medical research council formed in britain in 1913, it initially focused on tuberculosis research. in europe, rates of tuberculosis began to rise in the early 1600s to a peak level in the 1800s, when it caused nearly 25% of all deaths. in the 18th and 19th century, tuberculosis had become epidemic in europe, showing a seasonal pattern. by the 1950s mortality in europe had decreased about 90%. improvements in sanitation, vaccination, and other public-health measures began significantly reducing rates of tuberculosis even before the arrival of streptomycin and other antibiotics, although the disease remained a significant threat. in 1946, the development of the antibiotic streptomycin 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. because of the emergence of multidrug-resistant tuberculosis (mdr-tb), surgery has been re-introduced for certain cases of tb infections. it involves the removal of infected chest cavities ("bullae") in the lungs to reduce the number of bacteria and to increase exposure of the remaining bacteria to antibiotics in the bloodstream. hopes of eliminating tb ended with the rise of drug-resistant strains in the 1980s. the subsequent resurgence of tuberculosis resulted in the declaration of a global health emergency by the world health organization (who) in 1993. society and culture names tuberculosis has been known by many names from the technical to the familiar. phthisis (φθισις) is a greek word for consumption, an old term for pulmonary tuberculosis; around 460 bce, hippocrates described phthisis as a disease of dry seasons. the abbreviation tb is short for tubercle bacillus. consumption was the most common nineteenth century english word for the disease, and was also in use well into the twentieth century. the latin root con meaning 'completely' is linked to sumere meaning 'to take up