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allergies or NOT?
by mechanical and thermal stimuli or by mediators such as bradykinin and histamine results in a sneezing response. Cholinergic and sympathetic nerves are involved in congestion as they innervate glands and arteries in the upper respiratory system that supply the glands. Sympathetic stimulation often constricts arterial blood flow while cholinergic stimula- tion dilates arterial blood flow. These specific sensory nerves can also respond to a variety of neuropeptide neurotransmit- ters, which can cause or add to the bothersome symptoms. Researchers have identified more than 200 viruses that cause colds. Rhinoviruses are the most common viruses that cause colds in children and adults. Other viruses known to cause colds include coronaviruses, respiratory syncytial virus, para- influenza, adenoviruses, human metapneumovirus, and enteroviruses. A cold caused by a virus like the ones already mentioned can be accompanied by a bacterial coinfection (usually with group A beta-hemolytic streptococci) but is usu- ally rare in occurrence. When a virus like rhinoviruses enters the upper respiratory tract, it binds to intercellular adhesion molecule-1 receptors on respiratory epithelial cells in the nose and nasopharynx. Once inside the epithelial cells, the virus starts to replicate and infection spreads to other cells. Peak viral concentrations are achieved two to four days after initial inoculation, and the virus can be present in the naso- pharynx for up to 16-18 days. Once cells are infected by the virus, they release chemokine “distress signals” and cyto- kines then activate inflammatory mediators and neurogenic reflexes. Once these processes are activated, it results in the recruitment of additional inflammatory mediators, vaso- dilation, transudation of plasma, glandular secretion and stimulation of pain nerve fibers, and sneeze and cough reflexes. Inflammatory mediators and parasympathetic nervous system reflex mechanisms cause hypersecretion of watery nasal fluid. Viral infection ends once enough neutralizing anti- body (secretory immunoglobulin A [IgA] or serum IgG) leaks into the mucosa to attack the virus and end viral replication. Common cold viruses can be transmitted and spread by three mechanisms: hand contact (via direct contact with an infected person or via indirect contact with a contaminated environmen- tal surface), small particle droplets (droplet nuclei or aerosols)
Symptoms from the common cold are typically due to the body’s immune response to infection, rather than direct viral damage to the respiratory tract. Moreover, symptoms usually begin 1-3 days after the initial infection. A sore throat is typi- cally the first symptom to arise, followed by nasal symptoms. Cough develops in roughly 30% of patients by day 4 or 5. Other possible symptoms include malaise and conjunctivitis. Fever is uncommon in adults with a cold but may be present in chil- dren, although unlikely. A physical assessment of the patient suffering from a cold may include the following: slightly red pharynx with evidence of postnasal drip, nasal obstruction, and mildly to moderately tender sinuses on palpation. Host factors, such as age, underlying illnesses, and prior immunological experience, as well as the type of infecting virus play a major role in the intensity of symptoms and clinical signs of a cold. CLINICAL PRESENTATION OF COLDS Many researchers are conflicted about increased sus- ceptibility due to cold environments, sudden chilling, or exposure to central heating (low humidity); however, these contributing factors have yet to be proven. Walking outside barefoot, teething, and suffering from enlarged tonsils or ade- noids have also not been shown to increase susceptibility to viral upper respiratory infections such as the common cold. that become airborne from sneezing or coughing, or large par- ticle droplets (droplet transmission) that typically require close contact with an infected person. The most efficient mode of viral transmission is self-inoculation of the nasal mucosa or conjunctiva after contact with virus-laden secretions on ani- mate or inanimate objects. Many of the viruses that cause colds may remain viable on human skin for up to two hours. The risk of person-to-person transfer is dependent upon the amount of time people spend together, the proximity of their contact with one another, and the amount of virus shed by the infected patient. Increased susceptibility to colds has been linked to higher exposure rates, allergic disorders affect- ing the nose or pharynx, less diverse social networks, and weakened immune systems due to smoking, sedentary life- styles, chronic psychological stress, or sleep deprivation.
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