Celtnet Infectious Diseases Affecting Humans Infromation Page

Viruses

Top of the list here are viruses. Viruses are sub-microscopic organisms that cannot survive independently. Viruses are so small that they cannot be seen with ordinary microscopes and you need an electron microscope to see them. Viruses can only survive by infecting living cells before taking-over the molecular machinery of that cell to reproduce themselves. By its very nature, therefore, a virus is infective and can only survive by infecting other organisms.

Many of humanity's commonest and deadliest diseases are cuased by viruses. The list is extensive, but here are some examples: common cold, influneza (flu), HIV/Aids, Polio, Smallpox, Chickenpox, Whoping Cough, Rubella, Mumps, Measles, Herpes, Warts, cancer viruses, dengue fever, yellow fever... the list goes on and on. Because, by some definitions, a virus is not truly alive it's very difficult to cure viruses. Antibiotics do not work agianst viruses, so don't expect a does of antibiotics if you have cold or flu. All infectious viruses are potentially killers and the only way to be protected against them is by immunization.

Bacteria

Bacteria are single-celled organisms that represent the smallest form of what one could loosely call 'true life'. Bacteria have been around longer than any other form of life. As a result they live in and colonize each and every ecosystem and nieche on Earth. They are incredibly successful organisms and the vast majority are either beneficial or cause no harm. Indeed, the healt of the human gut is dependent on its many colonies of baciteria. Only a very few species of bacteria cuase diseas and these are classed as Pathogenic Bacteria.

Fungi

Fungi represent a large group of eukaryotic organisms that range from micro-organisms (yeasts and moulds) to fungi and mushrooms. They form their own kingdom of life, distinct from animals and plants. Fungi have cell walls like plants, but do not posess chlorophyll and they survive by consuming other organisms either through decay or directly as parasites. Indeed, many fungi are parasites on plants, animals (including humans) and even other fungi. Some fungi can cause serious diseases in humans, several of which may be fatal if untreated. These include aspergilloses, candidoses, coccidioidomycosis, cryptococcosis, histoplasmosis, mycetomas, and paracoccidioidomycosis. It should also be noted that immuno-deficient patients are particularly susceptible to disease by genera such as Aspergillus, Candida, Cryptoccocus, Histoplasma, and Pneumocystis. Other fungi, fungi can attack eyes, nails, hair, and especially skin, the so-called dermatophytic and keratinophilic fungi, and cause local infections such as ringworm and athlete’s foot. Spores from moulds and fungi are also a significant cause of allergies.

A good example of a fungal disease is Candida Yeast Infection (Thrush)

Protozoa

Protozoa repersent a diverse group of single-cell eukaryotic organisms, many of which are motile. Today they are typically classified as animal-like protists. Some protozoa are human parasites, causing human disease. Some of the most common human diseases caused by protozoa include: Malaria; Amoebiasis; Giardiasis; Toxoplasmosis; Cryptosporidiosis; Trichomoniasis; Leishmaniasis; Sleeping Sickness and Dysentery.

A good example of a protozoan disease is Malaria

Prions

Prions are unique in that they are infectious agents comprising proteins in a modified form. This is in contrast to all other known infectious agents (virus/bacteria/fungus/parasite) which must contain nucleic acids (either DNA, RNA, or both). The word prion, coined in 1982 by Stanley B. Prusiner, is a portmanteau derived from the words protein and infection. Prions are responsible for the transmissible spongiform encephalopathies in a variety of mammals, including bovine spongiform encephalopathy (BSE, also known as "mad cow disease") in cattle and Creutzfeldt–Jakob disease (CJD) in humans. All known prion diseases affect the structure of the brain or other neural tissue and all are currently untreatable and universally fatal.

A good example of a prion disease is Creutzfeld-Jacob disease.