The healthy individual is quite resistant to infection. With some infections such as tuberculosis, host resistance is a primary factor in determining the risk of active infection following exposure.
The Interferons are proteins produced by human host cells in response to viral invasion of the cell. The interferons usually influence the activity of nearby host cells, increasing their resistance to viral invasion and interfering with viral replication. This interferons also stimulate the immune system and are used in cancer treatment for this reason. Unfortunately, they have not proved to be as beneficial in the treatment of cancer or other immune-based diseases as expected.
Factors that decrease host resistance include:
- . Age (infants and the elderly);
- . Genetic susceptibility ;
- .. Immunodeficiency of any type;
- . Malnutrition;
- .. Chronic disease, including cardiovascular disease, cancer, and diabetes;
- ..Severe physical or emotional stress;
· The inflammation or trauma affecting the integrity of the skin or mucosa, including burns, lack of protective secretions, bladder catheters, or other invasive procedures. Sometimes infection occurs easily because of a very small break in the skin or mucous membrane, or in an area of inflammation. The loss of skin and other defenses in a burn patient often results in secondary infection at the site; and poor inflammatory response, for example, due to long-term glucocorticoid medication.
Severe or multiple infections are very common in homeless individuals, in whom multiple factors decrease host resistance. For example, poor nutrition, open lesions, inadequate hygiene, fatigue, lack of medical care, and possible drug or alcohol abuse combine to create a high risk of infection such as tuberculosis.
Prophylactic antimicrobial medication may be required by any individuals with low resistance prior to exposure to possible infecting microbes, for example, before an invasive procedure.
