Infections And Infestations

THE MOST COMMON CAUSE OF DISEASE is infection by microorganisms that find their way into internal body tissues, where they multiply and disrupt normal cell function. These organisms, which are…

Protozoa

Protozoa are single-celled organisms that feed by scavenging for particles and other microorganisms, such as bacteria, or by absorbing nutrients from their environment. Many types of protozoa live in moist…

Bacteria

Bacteria are microscopic single-celled organisms that are found in every environment. Some bacteria live in or on our bodies without causing disease. There are thousands of different types of bacteria,…

Viruses

Viruses are the smallest infectious organisms, and they are so tiny that millions of them could fit inside a single human cell. Viruses are only capable of reproduction inside a…