The Common Cold, or Seasonal Cold, is a predominantly mild and self-limiting viral infection of the upper respiratory tract. However, it is also one of the most frequent causes of school and job absenteeism in the developed world, and while the grand majority of cases clear up within 10 to 15 days of the onset of symptoms, severe complications have been known to arise in the elderly, infants, and immunosuppressed populations. On average, young children suffer between 4 and 8 colds each year, while most healthy adults anywhere between 2 to 5.
Like most respiratory viral infections, it shows a clear predominance of seasonal incidence. As such, the potential impact on the quality of life of the average individual should not be understated.
What causes the common cold?
A wide variety of virus families cause the common cold. For example, half of all cases are produced by Rhinovirus, while the other half is produced by the coronavirus, respiratory syncytial virus, adenovirus, and enterovirus.
How are these viruses transmitted?
For the infection to occur, these viruses, which are abundantly found suspended in the small droplets of water that permeate the mucous membranes of sick individuals, have to reach the nose of healthy individuals and penetrate their mucosal cells. Therefore, transmission depends almost entirely on close contact with an infected person, which is what exposes healthy individuals to virulent respiratory secretions.
Contamination of the hands with nasal secretions found in objects such as door handles, bathroom surfaces, kitchen utensils, and office equipment, is also a singularly powerful path of transmission of the viruses that cause the common cold.
Children of school age are the main subset of the population that is affected, as well as the main reservoir and source of transmission of these viruses.
Clinical Evolution of the Common Cold
The incubation period of the common cold ranges between 24 and 72 hours, while the average, expected duration of the symptomatology is one week. However, some individuals can experience symptoms for up to two weeks. Sick individuals become highly contagious 3 to 4 days after the onset of the first symptoms and can remain so for up to 3 weeks.
The main symptoms associated with the common cold are rhinorrhea, sneezing, nasal obstruction, pharyngeal discomfort, and irritative cough. Consequently, the Flu and the Common Cold are often mistaken for one another. However, the conditions differ in intensity and their inherent risk of complications, and so it is crucial that we learn to differentiate between them.
For example, while both diseases are viral and have similar symptomatology, they are each caused by different types of viruses. The most noticeable difference between the two diseases is the intensity of the symptoms. Unlike the cold, the flu is much more intense and is more profoundly debilitating. For example, the flu typically induces a much higher fever that can last for three days or more. Another difference is that the onset of the flu is sudden, while the common cold develops more gradually.
For many people, this is the first symptom of the common cold that manifests itself. In the presence of the common cold, the body’s white blood cells begin to actively fight off the viral infection and in this process produce highly inflammatory byproducts known as cytokines. These substances, in turn, inflame the lacrimal ducts, which carry tears from the eye to the nose, causing the ducts to clog and the tears to accumulate in the eye.
That is why, during a bout of the common cold, or the flu, the patient’s eyes become watery with secretions, which causes a high degree of discomfort. In some extreme cases, the common cold can lead to the appearance of conjunctivitis, which consists of a pronounced inflammation of the conjunctiva, or the transparent membrane that covers part of the eyeball and the inner portion of the eyelids. Conjunctivitis causes redness, itching, swelling, excessive tearing, and whitish secretions.