Infectious Diseases

Infection occupy organism's in body tissues by diseases causing agents, their reaction of host tissues to these organisms and  toxins  they produce   must be  sufficient  number and virulence to destroy normal tissue, illness  resulting from an infection. Infectious disease was also known as transmissible diseases or communicable disease, the immune system is a host defense system comprising many biological structures and processes within an organism that protects against diseases. An immune system identifies a variety of agents, like pathogens, from viruses to parasitic worms  and  distinguishes them from organism’s own healthy tissue.