What is the common cold?

The common cold is a respiratory infection caused by a virus. The primary symptoms are a sore throat, runny nose and cough. The symptoms last 4-14 days. The common cold can be caused by about ten different viruses. There are hundreds of sub-types of viruses.

Adults have a cold on average 2-4 times a year, and children 6-8 times a year. Colds occur year-round, but are most common every year in August, September and October.

Common colds are spread through hand contact or airborne particles that travel a short distance. Most viruses are only spread by close contact. The incubation period is usually 1-3 days. The illness is most infectious 1-3 days after onset of symptoms.

Colds typically start with a sore throat. A rhinitis and stuffy nose are worst 2-4 days after symptoms appear. A cough can continue for several weeks. The most common complications of colds are acute middle-ear and sinus infections, which are usually treated with antibiotics.

Rhinitis is treated with nasal sprays that reduce swelling of mucous membranes. Ibuprophen and paracetamol are standard medications for aches and fever. The effectiveness of cough medications is poor. The effectiveness of zinc on cold symptoms is conflicting, but many studies have shown that zinc lozenges
can reduce the duration and severity of symptoms. Unnecessary use of antibiotics should be avoided.

There are indications that probiotics, zinc, Echinacea and vitamin D reduce the incidence of colds and flu. Thorough washing of hands with soap after contact is critical in prevention.

Olli Ruuskanen
Professor emeritus of infectious diseases