Pathogenicity and Immunology; Host resistance and the immune response Case4


There are six characteristics of infectious disease agents which determine whether or not an infectious disease will be transmitted to and infect a host. These characteristics also influence the severity of the disease and even the outcome of the resulting infection. these characteristics are as follows:

Infectivity: The ability of the agent to enter a host and multiply to an infectious dose, thereby producing the infection or disease.
Pathogenicity: The ability of the agent to cause disease in an infected host.
Virulence: This term refers to the severity of the infection. A highly virulent strain of a disease agent will most always produce severe cases or death.
Toxigenicity: This term refers to the ability of the agent to produce a toxin. The resulting illness or disease is from the toxin produced by the organism/agent and not the microorganism itself.
Resistance: This term refers to the ability of the agent to survive under adverse environmental conditions. It is also a measure of the agent’s fragility.
Antigenicity: This term refers to the ability of the agent to induce antibody production in the host. Agents that have a high antigenicity have a very low reinfection rate, whereas, agents with a low antigenicity rate have a higher reinfection rate.
Based on the above list of the most significant characteristics of infectious disease agents please answer the following questions or complete the stated tasks:

Identify three characteristics that you consider to be of significant importance when identifying diseases which would place those persons in a community at greater risk. (Some diseases pose a greater threat to persons likely to be exposed as a function of the characteristics presented above than other diseases.) Therefore, another perspective on this question is as follows: "If you were exposed to a disease, which of the above characteristics would be of greater concern to you as an individual."
Justify your position on selecting the three characteristics of a disease agent that you believe place those exposed to it at a greater risk.
Briefly discuss why the remaining three characteristics of infectious disease pathogens were not considered by you to be as significant as those you identified above.


Epidemiologic research shows that most diseases usually spread from one person to the other.  This means that when one person in a population contracts a disease, the disease is likely to spread to others unless it is contained (Watts, 2003).  For example, HIV is transmitted from one person another through body fluids, Malaria is spread from an infected person through mosquitoes, and many others. The medium of transmission however differs from disease to disease. Apart from the mode of transmission, there are other characteristics of each disease that determines their threat to others when one person is infected. These characteristics include infectivity, pathogenicity, virulence, toxigenicity, resistance, and antigenicity (Watts, 2003).  Among these characteristics, the most significant ones when identifying diseases that place individuals in a given community a greater risk are toxigenicity, infectivity, and pathogenicity.