The Common Cold with Dr. Robert Jawetz
The common cold – the name sounds so benign. Every year, particularly during the winter months, colds cause untold misery to millions of Americans. Colds are not actually caused by a single virus, rather by a whole witch’s brew of them. About half of colds are caused by the rhinovirus family of viruses which has at least 100 known variants. Other causes include the coronavirus family (yes that one), the flu viruses, parainfluenza (which also causes croup), and the adenovirus family. In the United States, colds tend to circulate at their highest levels between September and May. Children under 6 are most affected, averaging 6-8 colds per year, each lasting around 14 days (daycare attendance probably increases the number of infections by 50-100%). This is why infants and toddlers often seem to have a runny nose all winter long. Older children and adults tend to average 2-4 colds per year, each lasting 5-7 days (longer in smokers).
So, what is a cold exactly? The most common symptoms are congestion, runny nose, and cough. Infants are likely to have fevers (temperature over 100.4F or 38C) as well. The presenting symptoms are often cough and congestion with runny nose joining the party on day 3. Of note, nasal discharge is often clear initially but becomes colored (yellow or green) within a few days. Coloring of the mucus is probably related to the increase in the number or enzymatic activity of white blood cells found in the discharge. Despite urban legend, coloring of the nasal discharge does not indicate bacterial superinfection or acute bacterial sinusitis.
How are colds transmitted? Not by cold exposure or going out with wet hair! These viruses are quite contagious and spread multiple ways. The first route is via small droplets which are produced when we talk, sing, or cough. The droplets linger in the air for a while and are inhaled. Sometimes these activities produce more of a fine mist called an aerosol. Aerosols can linger in the air for an extended period of time, leading to a high likelihood of virus transmission in poorly ventilated areas. Colds can also spread via large droplets produced by sneezing which then land on the eyes and nose when someone sneezes toward you and doesn’t cover up. Finally, cold viruses can be transmitted through direct contact like a handshake. Studies have shown that just 10 seconds of contact with a contaminated surface can transmit the virus which can live on human skin for 2 hours. The victim then contaminates themselves by touching their eyes or nose. Remember folks, wash your hands!
Why do these viruses make us sick? As with many other illnesses, the cause of our symptoms is not the virus per se, but the body’s response to the virus. Cold viruses typically only infect a small number of nasal cells. These infected cells then produce signaling chemicals called cytokines which act as a trumpet call for white blood cells to flood the nose leading to noticeable nasal symptoms 1-2 days after infection. Large numbers of white blood cells cause the yellow/white mucus whereas green mucus indicates the white blood cells are unloading their own chemical agents to control the infection. Other types of cytokines result in increased mucus production and often sore throats.
I’m sick, what can I do to feel better? Unfortunately despite decades of research we do not have many effective treatments for cold symptoms. Fever and sore throat pain can be treated with acetaminophen or ibuprofen (for infants older than 6 months). Coughs can be treated with honey (for children older than 1 year) and inhalation of steam from the shower. For children over 6 years there is some evidence to suggest that throat lozenges may help as well. Nasal congestion may respond to over the counter decongestants in adolescents and adults but rarely help in children and should not be used in young children (less than 6 years). Nasal saline drops or sprays may produce some improvement in symptoms, but there is no evidence to suggest that nebulized nasal saline helps. Antibiotics never help treat the common cold. Stay safe out there everyone!
