Signs and symptoms
Tuberculosis may infect any part of the body, but most commonly occurs in the lungs (known as pulmonary tuberculosis). Extrapulmonary TB occurs when tuberculosis develops outside of the lungs, although extrapulmonary TB may coexist with pulmonary TB. General signs and symptoms include fever, chills, night sweats,Pulmonary
If a tuberculosis infection does become active, it most commonly involves the lungs (in about 90% of cases). Symptoms may include chest pain and a prolonged cough producing sputum. About 25% of people may not have any symptoms (i.e., they remain asymptomatic). Occasionally, people may cough up blood in small amounts, and in very rare cases, the infection may erode into theExtrapulmonary
In 15–20% of active cases, the infection spreads outside the lungs, causing other kinds of TB. These are collectively denoted as extrapulmonary tuberculosis. Extrapulmonary TB occurs more commonly in people with aCauses
Mycobacteria
The main cause of TB is '' Mycobacterium tuberculosis'' (MTB), a small,Transmission
When people with active pulmonary TB cough, sneeze, speak, sing, or spit, they expel infectious aerosol droplets 0.5 to 5.0 µm in diameter. A single sneeze can release up to 40,000 droplets. Each one of these droplets may transmit the disease, since the infectious dose of tuberculosis is very small (the inhalation of fewer than 10 bacteria may cause an infection).Risk of transmission
People with prolonged, frequent, or close contact with people with TB are at particularly high risk of becoming infected, with an estimated 22% infection rate. A person with active but untreated tuberculosis may infect 10–15 (or more) other people per year. Transmission should occur from only people with active TB – those with latent infection are not thought to be contagious. The probability of transmission from one person to another depends upon several factors, including the number of infectious droplets expelled by the carrier, the effectiveness of ventilation, the duration of exposure, theRisk factors
A number of factors make individuals more susceptible to TB infection and/or disease.Active disease risk
The most important risk factor globally for developing active TB is concurrent HIV infection; 13% of those with TB are also infected with HIV. This is a particular problem in sub-Saharan Africa, where HIV infection rates are high. Of those without HIV infection who are infected with tuberculosis, about 5–10% develop active disease during their lifetimes; in contrast, 30% of those co-infected with HIV develop the active disease. Use of certain medications, such as corticosteroids andInfection susceptibility
Tobacco smoking increases the risk of infections (in addition to increasing the risk of active disease and death). Additional factors increasing infection susceptibility include young age.Pathogenesis
About 90% of those infected with ''M. tuberculosis'' have asymptomatic, latent TB infections (sometimes called LTBI), with only a 10% lifetime chance that the latent infection will progress to overt, active tuberculous disease. In those with HIV, the risk of developing active TB increases to nearly 10% a year. If effective treatment is not given, the death rate for active TB cases is up to 66%. TB infection begins when the mycobacteria reach the alveolar air sacs of the lungs, where they invade and replicate withinDiagnosis
Active tuberculosis
Diagnosing active tuberculosis based only on signs and symptoms is difficult, as is diagnosing the disease in those who have a weakened immune system. A diagnosis of TB should, however, be considered in those with signs of lung disease orLatent tuberculosis
ThePrevention
Tuberculosis prevention and control efforts rely primarily on the vaccination of infants and the detection and appropriate treatment of active cases. TheVaccines
The only availablePublic health
Public health campaigns which have focused on overcrowding, public spitting and regular sanitation (including hand washing) during the 1800s helped to either interrupt or slow spread which when combined with contact tracing, isolation and treatment helped to dramatically curb the transmission of both tuberculosis and other airborne diseases which led to the elimination of tuberculosis as a major public health issue in most developed economies. Other risk factors which worsened TB spread such as malnutrition were also ameliorated, but since the emergence of HIV a new population of immunocompromised individuals was available for TB to infect. The World Health Organization (WHO) declared TB a "global health emergency" in 1993, and in 2006, the Stop TB Partnership developed aTreatment
Treatment of TB uses antibiotics to kill the bacteria. Effective TB treatment is difficult, due to the unusual structure and chemical composition of the mycobacterial cell wall, which hinders the entry of drugs and makes many antibiotics ineffective. Active TB is best treated with combinations of several antibiotics to reduce the risk of the bacteria developing antibiotic resistance. The routine use ofLatent TB
Latent TB is treated with eitherNew onset
The recommended treatment of new-onset pulmonary tuberculosis, , is six months of a combination of antibiotics containing rifampicin, isoniazid, pyrazinamide, and ethambutol for the first two months, and only rifampicin and isoniazid for the last four months. Where resistance to isoniazid is high, ethambutol may be added for the last four months as an alternative. Treatment with anti-TB drugs for at least 6 months results in higher success rates when compared with treatment less than 6 months, even though the difference is small. Shorter treatment regimen may be recommended for those with compliance issues. There is also no evidence to support shorter anti-tuberculosis treatment regimens when compared to a 6-month treatment regimen. However recently, results from an international, randomized, controlled clinical trial indicate that a four-month daily treatment regimen containing high-dose, or "optimized," rifapentine with moxifloxacin (2PHZM/2PHM) is as safe and effective as the existing standard six-month daily regimen at curing drug-susceptible tuberculosis (TB) disease.Recurrent disease
If tuberculosis recurs, testing to determine which antibiotics it is sensitive to is important before determining treatment. If Multidrug-resistant TB, multiple drug-resistant TB (MDR-TB) is detected, treatment with at least four effective antibiotics for 18 to 24 months is recommended.Medication administration
Directly observed therapy, i.e., having a health care provider watch the person take their medications, is recommended by the World Health Organization (WHO) in an effort to reduce the number of people not appropriately taking antibiotics. The evidence to support this practice over people simply taking their medications independently is of poor quality. There is no strong evidence indicating that directly observed therapy improves the number of people who were cured or the number of people who complete their medicine. Moderate quality evidence suggests that there is also no difference if people are observed at home versus at a clinic, or by a family member versus a health care worker. Methods to remind people of the importance of treatment and appointments may result in a small but important improvement. There is also not enough evidence to support intermittent rifampicin-containing therapy given two to three times a week has equal effectiveness as daily dose regimen on improving cure rates and reducing relapsing rates. There is also not enough evidence on effectiveness of giving intermittent twice or thrice weekly short course regimen compared to daily dosing regimen in treating children with tuberculosis.Medication resistance
Primary resistance occurs when a person becomes infected with a resistant strain of TB. A person with fully susceptible Mycobacterium tuberculosis, MTB may develop secondary (acquired) resistance during therapy because of inadequate treatment, not taking the prescribed regimen appropriately (lack of compliance), or using low-quality medication. Drug-resistant TB is a serious public health issue in many developing countries, as its treatment is longer and requires more expensive drugs. MDR-TB is defined as resistance to the two most effective first-line TB drugs: rifampicin and isoniazid. Extensively drug-resistant TB is also resistant to three or more of the six classes of second-line drugs. Totally drug-resistant TB is resistant to all currently used drugs. It was first observed in 2003 in Italy, but not widely reported until 2012, and has also been found in Iran and India. There is some efficacy for linezolid to treat those with XDR-TB but side effects and discontinuation of medications were common. Bedaquiline is tentatively supported for use in multiple drug-resistant TB. XDR-TB is a term sometimes used to define ''extensively resistant'' TB, and constitutes one in ten cases of MDR-TB. Cases of XDR TB have been identified in more than 90% of countries. For those with known rifampicin or MDR-TB, molecular tests such as the Genotype® MTBDRsl Assay (performed on culture isolates or smear positive specimens) may be useful to detect second-line anti-tubercular drug resistance.Prognosis
Progression from TB infection to overt TB disease occurs when the bacilli overcome the immune system defenses and begin to multiply. In primary TB disease (some 1–5% of cases), this occurs soon after the initial infection. However, in the majority of cases, a Latent tuberculosis, latent infection occurs with no obvious symptoms. These dormant bacilli produce active tuberculosis in 5–10% of these latent cases, often many years after infection. The risk of reactivation increases with immunosuppression, such as that caused by infection with HIV. In people coinfected with ''M. tuberculosis'' and HIV, the risk of reactivation increases to 10% per year. Studies using DNA fingerprinting of ''M. tuberculosis'' strains have shown reinfection contributes more substantially to recurrent TB than previously thought, with estimates that it might account for more than 50% of reactivated cases in areas where TB is common. The chance of death from a case of tuberculosis is about 4% , down from 8% 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 nation, 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 andGeographical 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 (UK), 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;Global Tuberculosis ControlChina
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 (epidemiology), 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 theNorth America
In the United States Native Americans 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.History
Tuberculosis has existed since Ancient history, 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 Common Era, BC) had TB, and researchers have found tubercular decay in the spines of Egyptian mummy, 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 Dr Richard Morton, Richard Morton established the pulmonary form associated with tubercle (anatomy), 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. Johann Lukas Schönlein, 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 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 BCG vaccine, 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 List of notifiable diseases, notifiable-disease list in Britain; campaigns started to stop people from spitting in public places, and the infected poor were "encouraged" to enter sanatorium, 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 ( 1916). When the Medical Research Council (UK), 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, History of tuberculosis#Epidemic tuberculosis, 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. In India, tuberculosis prevalence was first investigated by Dr. Arthur Colborne Lankester, an English medical missionary and physician. He was selected by the government to undertake the study for one year and collaborate with all the provincial governments of India to expand the reach of the research. He eventually published a book titled ''Tuberculosis in India.'' ' Because of the emergence of Multidrug-resistant tuberculosis, 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 Antibiotic resistant, 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. () 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 (shape), bacillus''. ''Consumption'' was the most common nineteenth century English word for the disease. The Latin root meaning 'completely' is linked to meaning 'to take up from under'. In ''The Life and Death of Mr Badman'' by John Bunyan, the author calls consumption "the captain of all these men of death." "Great white plague" has also been used.Art and literature
Tuberculosis was for centuries associated with poetic and artistic qualities among those infected, and was also known as "the romantic disease". Major artistic figures such as the poets John Keats, Percy Bysshe Shelley, and Edgar Allan Poe, the composer Frédéric Chopin, the playwright Anton Chekhov, the novelists Franz Kafka, Katherine Mansfield, Charlotte Brontë, Fyodor Dostoevsky, Thomas Mann, W. Somerset Maugham, George Orwell, and Robert Louis Stevenson, and the artists Alice Neel, Jean-Antoine Watteau, Elizabeth Siddal, Marie Bashkirtseff, Edvard Munch, Aubrey Beardsley and Amedeo Modigliani either had the disease or were surrounded by people who did. A widespread belief was that tuberculosis assisted artistic talent. Physical mechanisms proposed for this effect included the slight fever and toxaemia that it caused, allegedly helping them to see life more clearly and to act decisively. Tuberculosis formed an often-reused theme in literature, as in Thomas Mann's ''The Magic Mountain'', set in a sanatorium; in music, as in Van Morrison's song "T.B. Sheets"; in opera, as in Giacomo Puccini, Puccini's ''La bohème'' and Giuseppe Verdi, Verdi's ''La Traviata''; in art, as in Claude Monet, Monet's painting of his first wife Camille on her deathbed; and in film, such as the 1945 ''The Bells of St. Mary's'' starring Ingrid Bergman as a nun with tuberculosis.Public health efforts
In 2014, the WHO adopted the "End TB" strategy which aims to reduce TB incidence by 80% and TB deaths by 90% by 2030. The strategy contains a milestone to reduce TB incidence by 20% and TB deaths by 35% by 2020. However, by 2020 only a 9% reduction in incidence per population was achieved globally, with the European region achieving 19% and the African region achieving 16% reductions. Similarly, the number of deaths only fell by 14%, missing the 2020 milestone of a 35% reduction, with some regions making better progress (31% reduction in Europe and 19% in Africa). Correspondingly, also treatment, prevention and funding milestones were missed in 2020, for example only 6.3 million people were started on TB prevention short of the target of 30 million. The World Health Organization (WHO), the Bill and Melinda Gates Foundation, and the U.S. government are subsidizing a fast-acting diagnostic tuberculosis test for use in low- and middle-income countries as of 2012. In addition to being fast-acting, the test can determine if there is resistance to the antibiotic rifampicin which may indicate multi-drug resistant tuberculosis and is accurate in those who are also infected with HIV. Many resource-poor places have access to only sputum microscopy. India had the highest total number of TB cases worldwide in 2010, in part due to poor disease management within the private and public health care sector. Programs such as the Revised National Tuberculosis Control Program are working to reduce TB levels among people receiving public health care. A 2014 Economist Intelligence Unit, EIU-healthcare report finds there is a need to address apathy and urges for increased funding. The report cites among others Lucica Ditui "[TB] is like an orphan. It has been neglected even in countries with a high burden and often forgotten by donors and those investing in health interventions." Slow progress has led to frustration, expressed by the executive director of the Global Fund to Fight AIDS, Tuberculosis and Malaria – Mark Dybul: "we have the tools to end TB as a pandemic and public health threat on the planet, but we are not doing it." Several international organizations are pushing for more transparency in treatment, and more countries are implementing mandatory reporting of cases to the government as of 2014, although adherence is often variable. Commercial treatment providers may at times overprescribe second-line drugs as well as supplementary treatment, promoting demands for further regulations. The government of Brazil provides universal TB care, which reduces this problem. Conversely, falling rates of TB infection may not relate to the number of programs directed at reducing infection rates but may be tied to an increased level of education, income, and health of the population. Costs of the disease, as calculated by the World Bank in 2009 may exceed US$150 billion per year in "high burden" countries. Lack of progress eradicating the disease may also be due to lack of patient follow-up – as among the 250 million migration in China, rural migrants in China. There is insufficient data to show that active contact tracing helps to improve case detection rates for tuberculosis. Interventions such as house-to-house visits, educational leaflets, mass media strategies, educational sessions may increase tuberculosis detection rates in short-term. There is no study that compares new methods of contact tracing such as social network analysis with existing contact tracing methods.Stigma
Slow progress in preventing the disease may in part be due to social stigma, stigma associated with TB. Stigma may be due to the fear of transmission from affected individuals. This stigma may additionally arise due to links between TB and poverty, and in AIDS in Africa, Africa, AIDS. Such stigmatization may be both real and perceived; for example, in Ghana, individuals with TB are banned from attending public gatherings. Stigma towards TB may result in delays in seeking treatment, lower treatment compliance, and family members keeping cause of death secret – allowing the disease to spread further. In contrast, in Russia stigma was associated with increased treatment compliance. TB stigma also affects socially marginalized individuals to a greater degree and varies between regions. One way to decrease stigma may be through the promotion of "TB clubs", where those infected may share experiences and offer support, or through counseling. Some studies have shown TB education programs to be effective in decreasing stigma, and may thus be effective in increasing treatment adherence. Despite this, studies on the relationship between reduced stigma and mortality are lacking , and similar efforts to decrease stigma surrounding AIDS have been minimally effective. Some have claimed the stigma to be worse than the disease, and healthcare providers may unintentionally reinforce stigma, as those with TB are often perceived as difficult or otherwise undesirable. A greater understanding of the social and cultural dimensions of tuberculosis may also help with stigma reduction.Research
The BCG vaccine has limitations, and research to develop new TB vaccines is ongoing. A number of potential candidates are currently in clinical trial, phase I and II clinical trials. Two main approaches are used to attempt to improve the efficacy of available vaccines. One approach involves adding a subunit vaccine to BCG, while the other strategy is attempting to create new and better live vaccines. MVA85A, an example of a subunit vaccine, is in trials in South Africa as of 2006, is based on a genetically modified vaccinia virus. Vaccines are hoped to play a significant role in treatment of both latent and active disease. To encourage further discovery, researchers and policymakers are promoting new economic models of vaccine development as of 2006, including prizes, tax incentives, and advance market commitments. A number of groups, including the Stop TB Partnership, the South African Tuberculosis Vaccine Initiative, and the Aeras Global TB Vaccine Foundation, are involved with research. Among these, the Aeras Global TB Vaccine Foundation received a gift of more than $280 million (US) from the Bill and Melinda Gates Foundation to develop and license an improved vaccine against tuberculosis for use in high burden countries. A number of medications are being studied as of 2012 for multidrug-resistant tuberculosis, including bedaquiline and delamanid. Bedaquiline received U.S. Food and Drug Administration (FDA) approval in late 2012. The safety and effectiveness of these new agents are uncertain as of 2012, because they are based on the results of relatively small studies. However, existing data suggest that patients taking bedaquiline in addition to standard TB therapy are five times more likely to die than those without the new drug, which has resulted in medical journal articles raising health policy questions about why the FDA approved the drug and whether financial ties to the company making bedaquiline influenced physicians' support for its use. Steroids add-on therapy has not shown any benefits for active pulmonary tuberculosis infection.Other animals
Mycobacteria infect many different animals, including birds, fish, rodents, and reptiles. The subspecies ''Mycobacterium tuberculosis'', though, is rarely present in wild animals. An effort to eradicate bovine tuberculosis caused by ''Mycobacterium bovis'' from the cattle and deer herds of New Zealand has been relatively successful. Efforts in Great Britain have been less successful. , tuberculosis appears to be widespread among captive elephants in the US. It is believed that the animals originally acquired the disease from humans, a process called reverse zoonosis. Because the disease can spread through the air to infect both humans and other animals, it is a public health concern affecting circuses and zoos.References
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