The sites which bacteria live and multiply are called reservoirs; the three main reservoirs of the pathogenic bacteria are humans, animals and non-living matters; the human body is considered to be a reservoir both in terms of the normal flora that inhabit it and the bacteria that can enter the body from exogenous sources; Diphtheria and Streptococcal infections are some of the disease that spread from human reservoirs and such diseases are called communicable.
Infectious diseases can also be transmitted from animals to humans; such diseases called zoonosis include cat scratch disease (CSD) also called cat scratch fever and rocky mountains spotted fever; pathogenic bacteria such as those that cause botulism can also thrive in the non-living reservoirs of soil and water; to transmit a disease from one organism to another; bacteria must first escape from the reservoir; each pathogen in a human reservoir has a specific area of the body from which it is shared; this area called a portal of exit is usually located at the area of infection; the most common portals of exit from human reservoirs are the openings of respiratory and gastrointestinal system;
Bacteria also leave the body via urogenital tract, wounds in the skin and blood; the respiratory system includes the nose, trachea and lungs; when a person coughs of sneezes microbes are expelled violently from the mouth and nose; examples of diseases caused by pathogens that exit via the respiratory tract are tuberculosis and pneumonia; components of the gastrointestinal system include the mouth, esophagus, stomach and large intestine and small intestines; pathogens depart the body from the gastrointestinal tract by means of saliva or feces; typhoid fever, cholera and polio can be transmitted from the host’s gastrointestinal tract to other hosts.
The urogenital system includes the kidneys, uritis, bladder, urethra the tubes through which urine is transported from the bladder out of the body and genital organs; bacteria can be carried out of the urogenital track through urine, semen and vaginal secretions; diseases caused by pathogens that leave through the urogenital tract include the sexually transmitted diseases (STDs).
When damaged; this skin can function as a portal of exit; since bacteria can escape from the body through open wounds; additionally infected blood may contain and transmit many pathogens; diseases caused by pathogens carried in blood include yellow fever and meningitis.
