Microorganisms such as bacteria, viruses, yeasts and molds can spoil food and may cause a risk to anyone's health. Microbes cause infectious diseases such as flu and measles. But you do have to remember that less than 1% of bacteria can invade our body (the host) and make us ill. So even if it is 1%, that's still 1% that can harm you.
Some examples of how microorganisms affect humans and how they can enter through your body:
Respiratory tract (mouth and nose): Influenza virus which causes the flu.
Gastrointestinal tract (mouth oral cavity): Vibrio cholerae which causes cholera.
Urogenital tract: Escherichia coli which causes cystitis.
Breaks in the skin surface: Clostridium tetani which causes tetanus.
