Infectious diseases also called communicable diseases are caused by pathogenic microorganisms (such as bacteria, viruses, parasites or fungi), they can be transmitted directly or indirectly from one person to another. Plague is a deadly infectious disease (ZOONOTIC DISEASE) caused by a gram negative bacterium Yersinia pestis. Plague is a disease that affects humans and other mammals. The bacteria are found primarily in rats and the fleas that feed on them. Plague is transmitted to humans or other animals by the bite of rats and fleas carrying the plague bacterium, by scratches of infected animals, by inhalation of aerosols or by consumption of food contaminated with the plague bacterium, i.e. Yersinia pestis. In the past the plague destroyed entire civilizations; no disease had such a profound impact on civilization as the plague in Egypt, Europe and Asia during the Middle Ages. As many as 200 million people died due to this disease.History of Plague DiseasePlague epidemics are grouped into 3 Plague Pandemics:-1. First plague pandemic known as JUSTINIAN'S PLAGUE, from approximately 541 to 750 AD. It spreads from Egypt to the Mediterranean and northwestern Europe. In Egypt, he destroyed 40% of CONSTANTINOPLE (a city in Africa) and went on to destroy up to 1/4 of the human population of the eastern Mediterranean. In Europe the population decreases by about 50% due to the plague.2. Second plague pandemic known as the BLACK DEATH, from 1345 to 1840. Spreads from Central Asia to the Mediterranean and Europe and probably also to China. It originates in or near China and spreads along the SILK ROAD. It may have reduced the world's population from 450 million to 350 million. Due to this disease, China has lost about half of its population...half of the paper......death rate if the patient is not treated within the first 24 hours of the first symptoms. the vaccine has been developed so far, scientists are working to develop the vaccine. Some key points to prevent plague are: -• Keeping the rat population under control: - This can reduce the risk of contracting the plague-causing Yersinia pestis bacterium.• Protect your pet from fleas by using a repellent for insects.• Avoiding all risk factors mentioned above.• If exposed to fleas during a plague epidemic, go to the doctor immediately.• Try to avoid visiting plague-endemic areas.• Prompt treatment should be undertaken if there are symptoms of pain in the lymph nodes.• Wear appropriate gloves and cloths if handling infected animals to prevent direct contact.• Do not allow animals such as dogs or cats to roam free in the endemic area.