Tuberculosis

Airborne Precautions

Contact Precautions

Tuberculosis (TB) is an acute or chronic infection characterized by pulmonary infiltrates and by the formation of granulomas with caseation, fibrosis, and cavitation. The incidence of TB has been declining in the United States, but its prevalence is increasing worldwide. According to the World Health Organization, approximately 2 billion people—one-third of the world’s population—have latent TB. Globally, TB is the leading infectious cause of morbidity and mortality, generating 8 to 10 million new cases each year and causing 3 million deaths.

The disease is twice as common in males as in females and four times as common in nonwhites as in whites. The incidence is highest in people who live in crowded, poorly ventilated, unsanitary conditions, such as prisons, tenement housing, and homeless shelters. The typical newly diagnosed patient with TB is a single, homeless, nonwhite man. With proper treatment, the prognosis is usually excellent. However, mortality is 50% in those with strains of TB that are resistant to two or more of the major antitubercular agents.

Causes

TB results from exposure to Mycobacterium tuberculosis and, sometimes, other strains of mycobacteria. Transmission occurs when an infected person coughs or sneezes, spreading infected droplets. After exposure to M. tuberculosis, roughly 5% of infected people develop active TB within 2 years. In the remainder, the microorganisms cause a latent infection. The host’s immunologic defense system usually destroys the bacillus or walls it up in a tubercle. However, the live, encapsulated bacilli may lay dormant within the tubercle for years, reactivating later to cause active infection. In this respect, the disease is an opportunistic infection.

The following at-risk populations incur a high incidence of TB with presenting symptoms:

Black and Hispanic males ages 25 to 44
People in close contact with a newly diagnosed patient with TB
Those who have already had TB
People with multiple sexual partners
Recent immigrants from Africa, Asia, Mexico, and South America
Gastrectomy patients
People with silicosis, diabetes, malnutrition, cancer, Hodgkin’s disease, or leukemia
Drug and alcohol abusers
Smokers
Patients in mental health facilities
Nursing home residents (they are 10 times more likely to contract TB than anyone in the general population)
Those receiving treatment with immunosuppressants or corticosteroids
People with weak immune systems or diseases that affect the immune system, especially acquired immunodeficiency syndrome (AIDS)
Prisoners
Homeless people

Complications

TB can cause massive pulmonary tissue damage, with inflammation and tissue necrosis eventually leading to respiratory failure. Bronchopleural fistulas can develop from lung tissue damage, resulting in pneumothorax. The disease can also lead to hemorrhage, pleural effusion, and pneumonia. Small mycobacterial foci can infect other body organs and systems, including the kidneys and the central nervous and skeletal systems. The patient also might develop complications such as liver involvement from drug therapy.

Assessment Findings

The patient with a primary TB infection after an incubation period of 4 to 8 weeks is usually asymptomatic but may complain of weakness and fatigue, anorexia and weight
loss, low-grade fever, and night sweats. The patient with reactivated TB may report chest pain and a cough that produces blood or mucopurulent or blood-tinged sputum. He or she may also have a low-grade fever.

Percussion may reveal dullness over the affected area (a sign of consolidation or the presence of pleural fluid). On auscultation, crepitant crackles, bronchial breath sounds, wheezes, and whispered pectoriloquy may be heard.

Diagnostic Tests

Several of the following tests may be necessary to distinguish TB from other diseases that may mimic it, such as lung carcinoma, lung abscess, pneumoconiosis, and bronchiectasis.