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Communicable Disease

Pathogens are disease-causing organisms which be classified into several main categories. The five categorical names and descriptions used by the text are viruses, bacteria, fungi, protozoa, and parasitic worms.

Viruses

A virus is the smallest and most simple of all pathogens. Their lack of elaborate structure makes them very difficult to control. As a result, most viral infections are not curable, although they can be treatable. Additionally, there are vaccines available for some viruses. Often, an inactive form of a specific virus is used for a vaccine; after it is injected, the body responds by forming temporary, semi-permanent, or permanent immunity against the particular virus. The common cold, influenza, herpes, genital warts, and AIDS are caused by viruses.

A SENSITIVE photo of a child with the measles--caused by a virus--is available through the Immunization Action Coalition (O). The Immunization Action Coalition also shows a sensitive photo of a child afflicted with polio (O--SENSITIVE photo). Web Path shows a magnified view of human immunodeficiency virus (HIV) under an electron micrograph (O).

The Public Health Image Library (PHIL) shows magnified images of a variety of viral pathogens, as well as photos of those infected with the viral conditions at their website (O). To find photos of infected patients as well as images of microscopic pathogens, travel to PHIL's search page, checkmark "photos" and type in the below examples (O):

Educational Enrichment

Quicktime clips associated with ebola virus infections, a thesis project from a Stanford student (please NOTE: some links are non-functional; the body bag link can be found at the following website: http://www.stanford.edu/group/virus/filo/bodybag.html)

Journal of Virology

The Big Picture Book of Viruses, a catalog of virus pictures on the Web, is available through Tulane University

Bacteria

A bacterium is a single-celled microscopic organism, although larger than a virus. Examples of bacterial infections include chlamydia, strep throat, diptheria, and tetanus. Merck.com shows shapes of bacteria (R). Many bacterial infections are curable with antibiotics or sulfa drugs, although some individuals are allergic to such medications. Unfortunately, some bacteria have become resistant to current drug treatments, due to the development of new bacterial strains. The reasons for resistance can be multifactorial, such as incomplete therapy, coexisting illness, poor living conditions, etc. An example of this problem is tuberculosis, seen in the United States. If interested, travel to the American Lung Association for general information about tuberculosis (O).

PHIL shows a variety of magnified bacteria images, including those listed below (O). To access the images, go to PHIL's search page, checkmark "photos," and search for the items listed (O):

Educational Enrichment

The World Health Organization has a 2004 publication titled antituberculosis drug resistance in the world

New York State Department of Health fact sheet about anthrax

Cells Alive!

MRSA Infection - Mayo Clinic Information

Fungi

A fungus is a plantlike organism and is not a large contributor of human diseases. Examples of fungi-related human afflictions include athlete's foot, "jock itch," and vaginal yeast infections. Such fungal infections can be treated and controlled. The University of Iowa Libraries site shows images of athlete's foot (O--WARNING: sensitive photos). Doctorfungus.org ("Dr. Fungus") provides a list and descriptions of human fungal infections (O-you may need to agree to a statement, then select "In People" under the "Think You Have a Fungal Infection" section).

PHIL shows a variety of magnified fungi images, including those listed below (O). To access the images, go to PHIL's search page, checkmark "photos," and search for the items listed (O):

Educational Enrichment

Fungal Infections of the Skin (American Academy of Dermatology)

Protozoa

Protozoa are very small single-celled organisms with wall structure different from bacteria and fungi. Examples of protozoan infections include malaria, giardiasis (O--DPDx image library), (O--DPDx image library), cryptospiridium (O--Centers for Disease Control),  trichomoniasis(R--DPDx video). If you cannot access the DPDxvideo clip, be sure to look at any of the DPDx images or one or more through Queensland University of Technology.

The Cells Alive! features a cryptospiridium movie (O); look for link in paragraph of content beneath images)

Educational Enrichment

The World Health Organization offers information on malaria

The Centers for Disease Control offers information about giardiasis

Droplet - Microscopy of Protozoa

Parasitic Worms

The term "parasitic worms" refers to multi-celled animals, some of them microscopic in size, others very large. Tapeworms, which reside in the gastrointestinal tract, and trichinosis are examples of parasitic worm infections. For a little more information, read the tapeworm description provided by Merck (R).

The University of California--San Diego's Division of Biological Sciences features a photo of an adult hookworm attached to a small intestine, feeding on (R).

If interested, look for parasitic infections by searching PHIL:

Educational Enrichment

The World Health Organization provides information on parasite control

The Family Information Library provides small descriptions of roundworms and tapeworms

The Center for Disease Control has information on alveolar echinococcosis, which results from a parasitic infection. Although it is mostly seen in coyotes, foxes, dogs and cats, it can also be transferred to humans.

Infection Prevention Online Course, from Engenderhealth

WormLearn, created by Dr. Peter Darben

The WHO Global Health Atlas allows the online viewer to research information related to communicable disease