The dividing line that separates the upper and lower respiratory tract is the larynx. Upper respiratory tract infections include strep throat, sinusitis, and the common cold. Lower respiratory tract infections include bronchitis and pneumonia. Influenza may affect both upper and lower respiratory structures.
The Common Cold
As stated previously, the common cold mostly affects the upper respiratory tract. It usually begins with a “scratchy” or sore throat followed by a runny nose and nasal congestion. Sneezing and coughing occur. A person with a cold may also feel very tired (malaise), have achy muscles and joints, experience a headache, and develop a hoarse voice. Fever is a common sign in children, but not common in adults.
Rhinoviruses are the most common cause of the common cold. Other causes are parainfluenza viruses, the respiratory syncytial virus (RSV), coronaviruses, and adenoviruses. In children younger than three years of age, infections are most commonly from RSV and/or the parainfluenza virus.
A virus that causes a cold is transmitted by either direct contact with a sick individual or contact with contaminated surfaces. These viruses can survive for at least 5 hours on hands and hard surfaces. Fingers are the main source of transmission. For this reason, the best way to avoid catching a cold is by washing your hands often and avoiding touching any of your mucus membranes with your fingers. The incubation period in a new host is around 5 days. A person is most contagious for the first 3 days after the onset of symptoms.
The condition is usually self-limiting and the immune system eliminates the pathogen within 10 days. Because a cold is caused by a virus, treating it with antibiotics is ineffective. If cold symptoms persist or get worse beyond 10 days, there may be a complication of a sinus infection or lower respiratory tract infection. This can be assessed by a healthcare provider.
Image by Becky T. BYU-I W20
Rhinosinusitis is inflammation of the nasal cavities and paranasal sinuses that is considered an upper respiratory tract infection. It is most often caused by allergies or an infection. In healthy individuals, the sinuses are normally filled with air and lined by a thin layer of mucous. With rhinosinusitis, the sinuses become clogged with secretions and mucus. Symptoms can include post-nasal drip, runny nose, nasal congestion, purulent nasal discharge, headache, sinus pain/pressure, loss of smell, and fever.
H. influenza, S. pneumoniae and Moraxella catarrhalis are the most common causes for community acquired bacterial rhinosinusitis. Potential complications from a bacterial sinus infection include meningitis and brain abscess. Rhinovirus is the most common cause for acute viral sinusitis. Rhinosinusitis can also be due to ostia narrowing and decreased drainage because of a damaged mucociliary escalator system, changes in pressure, decongestants, and dental infections.
The long-term use of decongestants to manage congestion is worth mentioning and warning against. It appears that the vasoconstricting effects of decongestants “wears off” over time. Through cellular upregulation of receptors and signals, the body adapts to the drug’s vasoconstriction effects to again cause vasodilation of the mucosal blood supply, which leads to increased mucus production. This upregulation eventually contributes to more congestion which can be further exacerbated if the drug is discontinued. Diagnosis of rhinosinusitis can be assisted by transillumination of the sinuses. This is done by shining light against the sinuses. Normally a sinus appears hollow and the light shining through gives off a reddish glow. When sinuses are inflamed and blocked with secretions and mucus, the light fails to shine through and the sinus appears opaque. This quick video can help you see what this looks like:
There are both non-pharmacological and pharmacological treatments that can be beneficial for those with rhinosinusitis. Non-pharmacological treatments include nasal spray and rinses and steam inhalation. Pharmacological treatments are antibiotics, steroids to suppress the immune system, mucolytic agents, and alpha agonists (which cause vasoconstriction to decrease mucus production).