Tuberculosis is a common infectious disease caused by various strains of mycobacterium. Tuberculosis typically attacks the lungs, but can also affect other parts of the body. It is spread through the air when people who have active TB infection cough, sneeze, or otherwise transmit their saliva through the air. If left untreated kills more than 50% of those so infected. The classic symptoms of active TB infection are a chronic cough with blood-tinged sputum, fever, night sweats, and weight loss.
Infection of other organs causes a wide range of symptoms. Tuberculosis has been present in Americans from about the year 100 AD, it was said to involve fever and coughing up of blood. Before the Industrial Revolution, often associated tuberculosis with vampires. Also when one member of a family dies from it, the other infected members would lose their health slowly. People believed this was caused by the original person with TB draining the life other family members.
Tuberculosis caused the most widespread public concern in the 19th and 20th centuries as an endemic disease of the urban poor. In 1815, one in four deaths in England was due to consumption. By 1918, one in six deaths in France was still caused by TB. In 1946, the development of the antibiotic streptomycin made effective treatment and cure of TB a reality. Prior to the introduction of this drug, the only treatment was surgical intervention, which involved collapsing an infected lung to rest it and allow tuberculosis lesions to heal.
Current surgical interventions involve removal of pathological chest cavities in the lungs to reduce the number of bacteria and to increase the exposure of the remaining bacteria to drugs in the bloodstream, thereby simultaneously reducing the total bacterial load and increasing the effectiveness of systemic antibiotic therapy. Hopes of completely eliminating TB were dashed after the rise of drug-resistant strains in the 1980s. A number of factors make people more susceptible to TB infections.
The most important risk factor globally is HIV; 13% of all TB cases are infected by the virus. 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 locals where vulnerable people gather (e. g. prisons and homeless shelters), medically underprivileged and resourced-poor communities, high-risk category patients and health care providers serving these clients.
Those who smoke cigarettes have nearly twice the risk of TB than nonsmokers, also alcoholism and diabetes increase the risk. The classic symptoms of active TB infection are a chronic cough with blood-tinged sputum, fever, night sweats, and weight loss. Infection of other organs cause a wide range of symptoms. General signs and symptoms include fever, chills, night sweats, loss of appetite, weight loss, and fatigue, and finger clubbing may also occur. If tuberculosis infection does become active, it most commonly involves the lungs.
Symptoms may include chest pain and a prolonged cough producing sputum. Tuberculosis may become a chronic illness and cause extensive scarring in the upper lobes of the lungs. 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, this occurs soon after the initial infection. However, in majority of cases, a infection occurs with no obvious symptoms. The risk of reactivation increases with immunosuppressant, such as that caused by infection with HIV.
In people co-infected with tuberculosis and HIV, the risk of reactivation increases to 10% a year. The chance of death from a case of tuberculosis is about 4% as of 2008, down from 8% in 1995. When people with active TB: coughing, sneezing, speaking, singing, or even spitting, they expel infectious droplets. 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 low (the inhalation of fewer than 10 bacteria may cause an infection).
People with prolonged, frequent, or close contact with people with TB are at particularly high risk of becoming infected. A person with active but untreated tuberculosis may infect 10-15 (or more) other people a year. 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, the virulence of the tuberculosis strain, the level of immunity in the uninfected person, and others.
After about two weeks of effective treatment, subjects with nonresistant active infections generally do not remain contagious to others. If someone does become infected, it typically takes three to four weeks before the newly infected person becomes infectious enough to transmit the disease to others. The only currently available vaccine as of 2011 is BCG which, while it is effective against disseminated disease in childhood, confers inconsistent protection against contracting TB. Nevertheless, it is the most widely used vaccine worldwide, with more than 90% of all children being vaccinated.
However, the immunity it induces decreases after about ten years. As tuberculosis is uncommon in most of Canada, the United Kingdom, and the United States, BCG is only administered to people at high risk. Part of the reasoning arguing against the use of the vaccine is that it makes the tuberculin skin test falsely positive, and therefore, of no use in screening. A number of new vaccines are currently in development. Tuberculosis prevention and control efforts primarily rely on the vaccination of infants and the detection and appropriate treatment of active cases.
There has been some success with improved treatment regimens, and a very small decrease in case numbers. A new fast-acting diagnostic test for use in low- and middle-income countries. Many resource-poor places as of 2011 still only have access to sputum microscopy. India had the highest total number of TB cases worldwide in 2010, in part due to poor disease management within the private health care sector. Programs are helping to reduce TB levels amongst people receiving public health care.