Infectious diseases are caused by pathogenic microorganisms such as bacteria, viruses, fungi or protozoa. Infectious diseases can spread via direct or indirect contact. Infections can be transmitted from animal to person (zoonotic) and from person to person. Diseases can spread through exchange of bodily fluids from sexual contact and during blood transfusion. It is also possible to contract an infectious disease from an inanimate object which has previously been contaminated with pathogen. Some infectious organisms live naturally in the surrounding environment but cannot be transmitted from person to person. Examples of these pathogens include anthrax (bacterial) and histoplasmosis or blastomycosis (fungal). R&D Systems offers tools for the study of Human Immunodeficiency Virus (HIV), Herpes virus, Influenza virus, and many more infectious diseases.