Definition of Pulmonary tuberculosis:

Pulmonary tuberculosis (TB) is a contagious bacterial infection that mainly involves the lungs, but may spread to other organs.

Causes, incidence, and risk factors:

Pulmonary tuberculosis is caused by a bacteria called Mycobacterium tuberculosis (M. tuberculosis). You can get tuberculosis by breathing in air droplets from a cough or sneeze of an infected person.

The primary stage of the infection is usually asymptomatic (without symptoms). In the United States, most people will recover from primary TB infection without further evidence of the disease. However, in some cases, the disease may become active within weeks after the primary infection, or it may lie dormant for years and later reappear.

The following are at higher risk for active TB:

• Elderly
• Infants
• Persons with weakened immune systems, for example due to AIDS, chemotherapy, or antirejection medicines given after a organ transplant

Your risk of contracting TB increases if you:

• Are in frequent contact with people who have the disease
• Live in crowded or unsanitary living conditions
• Have poor nutrition

The following factors that may increase the rate of tuberculous infection in a population:

• Increase in HIV infections
• Increase in number of homeless individuals (poor environment and poor nutrition)
• The appearance of drug-resistant strains of TB

In the United States, there are approximately 10 cases of TB per 100,000 people. However, rates vary dramatically by area of residence and socioeconomic class.

See also:

• Disseminated tuberculosis (affects the whole body)
• Atypical mycobacterial infection