A staph infection is a type of infection caused by the bacteria Staphylococcus. It can cause a range of symptoms, from mild skin infections to more serious illnesses such as pneumonia and meningitis. BACTERIAL infections are caused by bacteria, which are single-celled organisms that can cause a range of illnesses. Viral infections are caused by viruses, which are tiny infectious agents that can cause a range of illnesses, from the common cold to more serious illnesses such as HIV/AIDS. All three types of infection can be treated with antibiotics, although viral infections cannot be cured.