Section 3
Disease Patterns
By Boundless
![Thumbnail](../../../../../../figures.boundless-cdn.com/14372/square/za-seasonal-risk-areas.jpg.jpg)
The spread and severity of infectious disease is influenced by many predisposing factors.
![Thumbnail](../../../../../../figures.boundless-cdn.com/14397/square/76px-tuberculosis-symptoms.jpg)
After an pathogen invades a host, it undergoes a series of phases that eventually lead to multiplication of the pathogen.
![Thumbnail](../../../../../../figures.boundless-cdn.com/14409/raw/ead-of-swine-flu-in-europe.jpg)
Once discovered, natural reservoirs elucidate the complete life cycle of infectious diseases, providing effective prevention and control.
![Thumbnail](../../../../../../figures.boundless-cdn.com/14422/square/576px-ocd-handwash.jpeg)
Defining the means of transmission of a pathogen is important in understanding its biology and in addressing the disease it causes.
![Thumbnail](../../../../../../figures.boundless-cdn.com/14452/square/spread-of-the-black-death.gif)
Pathogens have evolved to adapt to their environment and their host in order to survive.
![Thumbnail](../../../../../../figures.boundless-cdn.com/14462/square/safety-level-4-hazmat-suit.jpeg)
Working with microorganisms, especially pathogens, requires special equipment and safety practices.
![Thumbnail](../../../../../../figures.boundless-cdn.com/14472/square/er-polluting-food-a-poster.jpeg)
The index case is identified in epidemiology studies by tracking down the infected patients to try to determine how the disease originated.