Emerging infectious disease are those diseases which recently appeared within the population and rapidly increasing as these are communicable diseases. It is threatens in future as well. These diseases increased from almost last 20 years and the increasing rate is 12% of all pathogens. But the irony is that 75% of population is still unaware about the causes, factors, reasons and consequences of these diseases. The research studies show the factor, causes, examples of emerging and re-emerging diseases which will help to the reader to develop the understanding with these new diseases.