While in colloquial terms, the "flu" can refer to any seasonal upper respiratory virus, and "stomach flu" indicates a viral inflammation of the digestive tract, true flu is short for influenza, which is caused by a virus of the family Orthomyxoviridae. The virus enters the respiratory tract and affects the lungs, with certain symptoms becoming systemic.
Identification
The early effects of the flu on body systems help physicians diagnose it, and prescribe either a course of treatment or palliative relief. In contrast to seasonal cold viruses, which typically start slowly with sneezing or coughing and become increasingly severe with time, the flu starts quite suddenly and dramatically, notes Boulder County Public Health. Early symptoms include sudden onset of headache and fever, chills, cough, and body aches. While early respiratory symptoms are the result of direct viral infection, other symptoms occur as a product of immune response.
Function
The function, or pathophysiology, of the flu virus is not completely known. Dr. Jacquelyn Black, in her book "Microbiology," notes that one of the flu virus's major functions is to inhibit adrenocorticotropic hormone, or ACTH. This hormone, produced by the anterior pituitary gland of the brain, has receptors on the adrenal cortex. It causes the cortex to produce and secrete cortisol. The virus enters the body by binding to cells in the respiratory tract, and using those cells as a point of entry.
Considerations
While the flu is a respiratory virus in the sense that it enters at a point in the respiratory tract, symptoms become systematic as a result of the body's immune system reaction to the virus. For instance, one early response is fever, a mechanism for raising the body's temperature. Fevers, explains Dr. Lauralee Sherwood in her book "Human Physiology," help raise the body temperature above that which is optimal for viral or bacterial reproduction. Chills and muscle aches can occur as a result of a fever.
Misconceptions
Because flu has to bind to receptors in the respiratory system in order to enter the human body and affect systems, many individuals wonder why the respiratory cells have receptors for the flu virus. In fact, the flu virus like all viruses, is merely opportunistic, explains Dr. Black. Existing receptors on cells that bind other proteins bind to proteins on the virus itself, allowing the virus to enter the cell. In the specific case of the flu virus, it's a viral protein called hemagglutinin that binds to cell receptors.
Prevention/Solution
The flu's effect on body systems results in discomfort of the illness, and since flu is viral, it can't be treated with antibiotics. Flu caught early may benefit from treatment with an antiviral like oseltamivir, explains Boulder County Public Health. Palliative treatments include staying well hydrated, using blankets or cool cloths as appropriate to control chills and fever, and sipping warm or cool, clear fluids. Very severe cases may require a doctor visit or hospitalization.
References
- "Microbiology: Principles and Explorations"; Jacquelyn Black; 2008
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
- Boulder County Public Health: Influenza
