San 3 - Organisms that Cause Disease



Part 3: Organisms that Cause Disease


Before reviewing cleaning and disinfecting procedures, it will be helpful to understand more about the types of microorganisms that cause disease. Many organisms are carried in the human body and remain harmless, but sometimes those organisms trigger serious disease. The microorganisms, or pathogens, that pose potential problems can be divided into three broad categories: viruses, bacteria and fungi.1




Viruses are infectious organisms that lack the usual structures found in cells, so they can only survive and reproduce by taking over cells in the body. Once inside a cell, they can replicate and invade other cells, thus spreading illness. Some of the common illnesses caused by viruses are colds, cold sores, chicken pox, measles, mumps, rubella, influenza (flu,) hepatitis,  cytomegalovirus (CMV,) respiratory syncytial virus (RSV,) polio and human immunodeficiency virus (HIV.)


The transmission of some viruses is easily prevented with simple precautions, but some are more resistant and require stronger chemical products. The susceptibility to disinfectant products depends on the structure of the virus, and researchers are still learning about the different structures of viruses and how they act within the body. The nature of viruses is what makes it so difficult to develop medicines to treat the illnesses they cause. Although vaccines exist for some viral infections (polio, measles and chicken pox, for example,) no cure has been developed for some of the more common viral illnesses such as colds. Antibiotics work on bacterial infections, but not on viruses.




Bacteria are single-celled organisms that contribute some of the best and the worst to human life. On the plus side, different types of bacteria produce large amounts of oxygen in water, help to turn milk into cheese and yogurt, convert free nitrogen into forms that plants can use to grow, produce the antibiotic streptomycin, and produce the enzyme that makes DNA fingerprinting and gene sequencing possible. However, other bacteria can produce anthrax, tuberculosis and staphyloccus (“staph”) and streptococcus (“strep”) infections.


Bacteria with spores are among the toughest microorganisms. Tetanus (lockjaw) and botulism are two of the most dreaded of illnesses caused by bacteria with spores, but a vaccine exists for tetanus. More common illnesses such as staphylococcus aureus, salmonella and the coliforms are caused by vegetative bacteria.




Molds and mildew are common fungi. They pose environmental hazards when buildings become contaminated with molds that can become airborne and cause serious allergic reactions in some people.


This extensive cast of health-threatening microorganisms should prompt serious attention to procedures to prevent the possible transmission of disease. While many objects may be safe without these precautions, AT center staff and future users are best protected by the implementation of standard practices for cleaning and disinfecting equipment.

  ________________ 1 “Meet the Microbes,” Microbe World. Retrieved February 4, 2008, from



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This work is supported under a five-year cooperative agreement # H235V060016 awarded by the U.S. Department of Education, Office of Special Education and Rehabilitative Services, and is administered by the Pass It On Center of the Georgia Department of Labor – Tools for Life.  However, the contents of this publication do not necessarily represent the policy or opinions of the Department of Education, or the Georgia Department of Labor, and you should not assume endorsements of this document by the Federal government or the Georgia Department of Labor.


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Title: San 3 - Organisms that Cause Disease
Module: Program Operations
Author: Trish Redmon
Audience: Implementer
Sub Title:
Organization Source: Pass It On Center
Last Reviewed: 10-25-2009 6:03 PM