Open Outbreak

Tuberculosis

Also known as: TB, Mycobacterium tuberculosis, MDR-TB

Tuberculosis is an infection caused by Mycobacterium tuberculosis. It usually affects the lungs, but it can also spread to lymph nodes, the brain, bones, kidneys, and other parts of the body. It spreads through the air when a person with lung or throat TB releases tiny infectious particles, so it is mainly a disease of close indoor exposure rather than casual contact with surfaces. A key feature of TB is latency: many people are infected without feeling ill, but some later develop active disease. Active TB commonly causes a long-lasting cough, fever, night sweats, weight loss, and sometimes coughing blood. Untreated disease can be fatal. Treatment exists, but it usually needs several antibiotics taken for months, and drug-resistant TB is harder to cure. A vaccine, BCG, has long been used in many countries, mainly to protect young children against severe forms of TB; it does not reliably prevent all adult lung TB. Important public-health concerns are delayed diagnosis, airborne spread in crowded settings, and drug resistance.

Key facts

TransmissionAirborne spread from a person with pulmonary or laryngeal TB through infectious aerosol droplets/particles released into the air.
Incubationunknown
Case fatalityunknown; available sources here state untreated TB can be fatal but do not give a single case-fatality figure.
Reproduction numberunknown
VaccineBCG vaccine exists and is widely used; available sources here support its use but do not give a single efficacy figure.
TreatmentCombination antibiotic treatment is available; drug-resistant TB, including MDR-TB and XDR-TB, is harder to treat.
ReservoirHumans are the main reservoir for Mycobacterium tuberculosis.
Endemic regionsWorldwide.

Transmission

Tuberculosis spreads mainly through the air. The available sources describe pulmonary TB as starting when Mycobacterium tuberculosis in aerosol droplets is deposited in the lungs. This means the main risk is breathing shared air with a person who has infectious TB of the lungs or throat, especially in crowded or poorly ventilated indoor spaces. TB is not usually thought of as spreading through food, water, or brief contact with objects. Another important point is that infection and illness are not the same thing. Some people become infected but have latent TB, meaning they do not feel ill and do not have signs of active disease. A smaller share later progress to active TB. For public health, this makes rapid diagnosis, ventilation, masking in high-risk settings, and treatment especially important, because untreated active pulmonary TB can keep spreading infection to others over time.

Symptoms and severity

Active TB most often affects the lungs. The overview source lists a chronic cough, mucus that can contain blood, fever, night sweats, and weight loss as typical symptoms. TB can also affect organs outside the lungs, including bone and the central nervous system, so symptoms can vary widely depending on where the infection is. Severity also varies. Some infections remain latent, with no symptoms at all, while active disease can become severe and life-threatening if it is not treated. The sources available in this session support the broad point that untreated TB can be fatal, but they do not provide a single overall case-fatality percentage that fits all settings and all years, so that figure is best treated as unknown here. People with weakened immune systems are at higher risk of progression from latent infection to active disease, which is one reason TB remains a major global health problem.

Treatment and vaccines

TB is treatable, but treatment is not simple. The sources available here support standard medical treatment with combinations of antibiotics, usually over months rather than days. This long course matters because incomplete treatment can allow the infection to continue and can help select for resistant strains. Drug-resistant TB is a special concern. The WHO outbreak notice in 2007 highlighted extensively drug-resistant TB, showing that resistance can complicate care and public-health response. Multidrug-resistant TB, often called MDR-TB, is also part of the disease picture and generally requires harder, longer, and more specialized treatment. A vaccine exists: BCG. The sources in this session support that it is used against TB, especially as part of long-standing control programs, but they do not give a single summary efficacy number for all ages and disease types. In plain terms, TB has tools against it, but they work best with early diagnosis, full treatment, and strong follow-up.

Where it occurs

Tuberculosis occurs worldwide. The sources available here describe TB as one of the oldest known human diseases and discuss its global dissemination, which supports a plain-language conclusion that no single region can be treated as the only place where it matters. Some strains, including the Beijing/W genotype discussed in one review, have been reported across many countries and have been linked in some settings to drug resistance. That does not mean every place has the same burden. TB risk is shaped by crowding, poverty, HIV prevalence, access to diagnosis, and the strength of treatment programs. Still, from a public-health point of view, TB is a global disease rather than a local curiosity. It remains relevant in high-burden countries, but it also appears in lower-burden countries through ongoing local transmission, reactivation of latent infection, and migration or travel. The main reservoir in the available sources is humans, which is why sustained community and health-system control measures matter so much.

Recent history

For this site, the archive count supplied with the request is 0 WHO notices since 1996 and 0 records. Even so, the WHO Disease Outbreak News search in this session did find a tuberculosis-related item from 2007 about an air passenger with extensively drug-resistant TB in the United States. That notice is not evidence of a global TB surge by itself, but it does show the kind of event that draws international attention: travel linked to a highly resistant form of the disease. More broadly, the literature found here describes TB as an old but still major infectious disease, with continuing concern about latent infection, transmission, and resistant strains. So the recent history, based on the limited sources retrieved in this session, is less about sudden outbreaks and more about persistent worldwide burden plus intermittent WHO attention when unusual or resistant cases create cross-border concern.

What to watch

The main warning signs for TB becoming more concerning are clear in the sources available here. First is more airborne spread in new settings, especially crowded indoor places where infectious pulmonary TB can pass through shared air. Second is more drug resistance. MDR-TB and especially XDR-TB make treatment more difficult and raise the risk of prolonged infectiousness. Third is spread across borders, including travel-associated events that attract WHO attention. Fourth is any widening gap between diagnosis and treatment, because TB can stay hidden as latent infection and then reappear as active disease later. Vaccine supply and use are also worth watching: BCG is an established tool, and problems with access could weaken protection for children against severe forms of disease. Finally, watch whether resistant strains become more common in places where TB burden was previously lower, because that would make routine control harder and could require stronger infection-control measures.

Updated