Infectious diseases are caused by the pathogenic microbial organisms. These microbes can multiply and can cause an infection, once they enter the body. Infectious diseases are transmissible, and may cause mild to life-threatening illnesses. It can be airborne, waterborne, foodborne, and soilborne. It can be spread through direct contact (human to human, animal to human). It has also been one of the leading causes of human deaths. Therefore, there is a need to have rapid diagnostic methods to prevent and control these diseases. This book titled "Diagnosis of Pathogenic Microorganisms Causing Infectious Diseases" will help the scientific community to understand the transmission dynamics of some infectious diseases of public health importance.