EPIDEMIOLOGY• WHO declared TB a global emergency in 1993.• Worldwide, one person in three is infected with TB.• About 8 million people develop disease every year• It kills more than 3 million people annually. Yet it is completely curable and (relatively) inexpensive to cure.
EPIDEMIOLOGY IN PAKISTAN• Pakistan ranks 6th amongst the countries with a highest burden of TB in the world.• TB is responsible for 5.1 percent of the total national disease burden in Pakistan.• Pakistan contributes about 44% of tuberculosis burden in the Eastern Mediterranean Region.• According to WHO, the incidence of sputum positive TB cases in Pakistan is 80/100,000 per year and for all types it is 177/100,000.
ETIOLOGY• TB is caused by an organism called Mycobacterium tuberculosis that is spread from person to person through the air. M. tuberculosis organisms are sometimes called tubercle bacilli. Some characteristics Of M. tuberculosis:• Slightly curved rod shaped bacilli• Thick lipid cell wall• Can remain dormant for years• Aerobic• Non-motile• Multiplies slowly (18-24 hrs)
HOW IS TB TRANSMITTED?• When a person with infectious TB disease coughs or sneezes, droplet nuclei containing tubercle bacilli may be expelled into the air. Other people may inhale the air containing these droplet nuclei and become infected.• Less frequently, TB can be transmitted by: Ingestion of Mycobacterium bovis found in unpasteurized milk products. Laboratory accident.
• Millions of tubercle bacilli in lungs (mainly in cavities)• Coughing projects droplet nuclei into the air that contain tubercle bacilli• One cough can release 3,000 droplet nuclei• One sneeze can release tens of thousands of droplet nuclei
PATHOGENESIS• As the TB tries to spread to other parts of the body, it is often interrupted by the bodys immune system. The immune system forms scar tissue or fibrosis around the TB bacteria, and this helps fight the infection and prevents the disease from spreading throughout the body and to other people.
ACTIVE TB INFECTIONGerms:• Awake and multiplying• Cause damage to the lungs Person:• Most often feels sick• Contagious (before pills started)• Usually have a positive tuberculin skin test• Chest X-ray is often abnormal (with pulmonary TB)
LATENT TB INFECTION• If the bodys immune system is unable to fight TB or if the bacteria breaks through the scar tissue, the disease returns to an active state with pneumonia and damage to kidneys, bones, and the meninges that line the spinal cord and brain. Person:• Not ill• Not contagious• Normal chest x-ray• Usually the tuberculin skin test is +ve Germs:• Sleeping but still alive• Surrounded (walled off) by body’s immune system
WHO GETS TUBERCULOSIS?Although anyone can become infected with TB, some people areat a higher risk, such as:• Those who live with others who have active TB infections• Overcrowded habitations• Poor or homeless people• Foreign-born people who come from countries with endemic TB• Older people, nursing home residents, and prison inmates• Alcoholics and intravenous drug users• Those who suffer from malnutrition• Diabetics, cancer patients, and those with HIV/AIDS or other immune system problems• Health-care workers• Workers in refugee camps or shelters