intro: It's the cause of death for nearly 1.5 million people each year mostly in developing countries. Tuberculosis (TB) is a lung disease that is caused by bacteria. The symptoms include fever, bloody cough and fatigue. World Tuberculosis Day is observed March 24 to "raise awareness about the burden of tuberculosis (TB) worldwide and the status of TB prevention and control efforts," according to the World Health Organization. Here are five things you didn't know about tuberculosis.