Pathogen

A pathogen is a biological agent that can cause disease, otherwise known as an infectious agent. They are disease causing organisms that grow and multiply within a host.

There are many types of pathogens. Listed on this page (below) are some specific examples of pathogens, shown organized into major categories. The term "pathogen" is most often applied to infectious biological agents that disrupt the normal physiology of multicellular animals or plants. There are also infectious agents that disrupt the normal physiology of unicellular organisms from all of the kingdoms (see Viruses, below). For example, the cells of a pathogenic strain of Escherichia coli may themselves be infected and destroyed by a virus. While many pathogenic viruses directly infect human cells, some viruses can indirectly effect human health by modulating the pathogenicity of bacteria, fungi or protozoa that infect humans.

Table of contents

1 Bacteria 2 Viruseses 2.1 Viruses can modulate the effects of fungal and bacterial pathogens 3 Subviral pathogens 4 Infectious fungi 5 Parasites 6 See also

Bacteria

• Escherichia coli
• Mycobacterium tuberculosis (tuberculosis)
• Neisseria gonorrhoeae
• Neisseria meningitidis (meningococcus) - see meningitis
• Rickettsiae
• Salmonella
• Staphylococcus aureus
• Streptococcus pyogenes
• Treponema pallidum
• Yersinia pestis

Viruseses

• Cytomegalovirus
• Hantaviruses (including the Sin Nombre virus, which causes HPS)
• Hepatitis (note that Hepatitis A and Hepatitis E are transmitted via the faecal-oral route)
  • Hepatitis B
  • Hepatitis C
  • Hepatitis D
• Herpes simplex virus
• Human Immunodeficiency Virus /HIV associated with AIDS
• Molluscum contagiosum
• papillomavirus, know to cause warts. Similar viruses are believed to contribute to cervical cancer.
• SARS (Severe Acute Respiratory Syndrome)

• TMV Tobacco mosaic virus. (a plant virus)

Viruses can modulate the effects of fungal and bacterial pathogens

• hypovirus CHV1 (Cryphonectria hypovirus 1, host organisms are fungi)
• Lambda phage is a virus that infects the eubacterial organism Escherichia coli.
• Thermoproteus tenax virus (TTV1) (host organisms are members of the kingdom Archaea)

Subviral pathogens

• prions
• viroids

Infectious fungi

• Pneumocystis jerovici has been proposed to replace the name Pneumocystis carinii, and reflect a new classification of this organism as an Archiascomycetous fungus. See: Pneumocystis_carinii_pneumonia.

Parasites

• giardia lamblia
• roundworms
• scabies
• tapeworms

See also

• foodborne illness
• Virulence