Tuberculosis is one of the oldest diseases known to affect humans, caused by Mycobacterium
Tuberculosis bacteria. More than 3.8 million cases were reported worldwide to the WHO in 2001, but because of lower levels of reporting, it is estimated that there were more than 8.5 million new cases in 2001. Ninety-five percent in Asia, around 5 million, and 2 million are thought to be in Africa. There were 1.8 million deaths from tuberculosis, 98% were from developing countries. It usually affects the lungs, but in about 35% of cases, other organs are affected as well. It is treatable in almost all cases, but if left untreated can be fatal in 5 years.
Natural Course of Illness
Exposure
The disease is transmitted from infectious patients with pulmonary TB to others by droplets. The bacilli that causes the illness is called *acid-fast* because of its high attraction to mycolic acid. AFB, or acid-fast bacilli are present in the sputum and transmitted by coughing, and sneezing. The droplet may remain in the air for several hours and may gain access to the air passages of other people when inhaled. Patients who have AFB negative respiratory cultures and those with extra pulmonary tuberculosis are less infectious. About 20 new people may be infected by each AFB positive patient.
Infection to Disease
Once infected, developing the disease may depend on the exposed person’s immunity. The clinical disease that immediately follows the exposure is called Primary Tuberculosis. It is usually seen in children up to 4 years. It may be severe but not transmittable in children. In older patients, primary TB is usually mild. Majority of infected patients who develop TB do so in 1-2 years. Usually, lesions heal and remain dormant. Dormant lesions that develop later in life become secondary TB. The risk of developing the disease is higher in adolescents and young adults. And it also increased in the elderly because of decreased immunity.
Risk factors that increase development of the disease include: HIV positive and decreased immunity. Untreated TB is often fatal. One- third die in one year, and half in five years.
Symptoms- Clinical Presentation
TB usually affects the lungs, but in about 35% of cases, other organs are affected as
well. Tuberculosis is classified as pulmonary and extra pulmonary, i.e TB
affecting lungs and other organs respectively.
Pulmonary TB which affects the lungs, can be categorized as primary and secondary. Primary TB presents as lesions in the lung and enlargement of the lymph nodes. The lung lesion usually heals and leaves a scar in the lung. In patients with decreased immunity, primary TB may progress rapidly into clinical disease. The primary site of infection enlarges, leading to the formation of a cavity in the lung. Lymph nodes may be enlarged, and other presentations may be fluid in the pleura- or a
pleural
effusion, pus in the pleura or empyema and bronchiectatsis. The bacilli can also get into the blood stream and form lesions in different parts of the body,
including meninges or the covering of the brain.
Secondary TB usually occurs in adults because of the activation of the bacilli that are dormant in the primary nodules. This can lead to cavities, and the patient becomes very ill, but most respond well to treatment.
Signs and Symptoms of secondary TB include:
- cough
- fever
- weight loss
- night sweats
- anorexia
- weakness
- blood in the sputum
- chest pain which is increased while breathing
- shortness of breath may be caused by extensive disease
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