The Common Cold

Common Cold Overview

• Common cold, also known as viral rhinitis, is an inflammation of the mucous membranes lining the nose.
• These membranes are found throughout the body's exposed areas.
• Estimated over a billion colds occur annually in the U.S.
• Usually not serious, lasting about 7-10 days.
• Can affect the nasal cavities, throat, larynx, and trachea.
• Commonly causes school/work absences.

Transmission

• Viruses enter mucous membranes (nostrils, mouth, eyes).
• Contact with surfaces carrying the virus then touching exposed areas spreads the virus.
• Inhaling virus-carrying air can transmit the infection.
• Close contact with infected people's secretions, as well as touching fomites (contaminated surfaces), spreads the cold.
• Viruses bind to receptors on cells in the mucous membranes, gaining entry.
• Many viruses are circulating constantly, with seasonal variations.
• More colds occur during colder months, due to enclosed spaces, close proximity, increased indoor time, and lower humidity.

Reducing Risk

• Frequent hand washing is crucial for preventing spread.
• Avoid touching the face (especially without washing hands).

Symptoms

• Symptoms appear one to three days after exposure.
• Common symptoms include sore throat, runny nose, cough, sneezing, headache, body aches.
• Fever is uncommon, except in children.
• Symptoms in a cold include sore throat, runny nose, sneezing, coughing, headache, fatigue, possibly joint pain.
• Symptoms commonly excluded from a cold are shortness of breath, diarrhea, and itchy eyes.

Cold vs. Flu vs. Allergies (Hay Fever)

• Symptoms can overlap, making diagnosis challenging.
• A cold typically involves a sore throat, runny nose, sneezing, coughing, headache, fatigue, and joint pain, often without fever (except in children) and without shortness of breath, diarrhea, and itchy eyes.
• Flu symptoms are usually more severe and include cough, headache, fever, fatigue, and joint pain, which are more frequent in flu.
• Cold viruses are different from the flu, COVID-19, and allergies. Allergies (or hay fever) have different characteristics.

Common Cold Viruses

• Rhinoviruses: Most common cause, over 100 serotypes (antigenically different).
  • Stable against detergents and heat, but sensitive to stomach acid.
  • Replicates best at 33-35°C (body temperature is 37°C, but cooler near the surface of the nose).
  • Spread through the air and on surfaces.
  • RNA virus, lacks an envelope, icosahedral, positive sense single-stranded RNA.
• Human Coronaviruses: Large family, infect many animals and may spillover into humans.
  • Seven human coronaviruses, four of which cause mild upper respiratory infections (including the common cold).
  • Spreads through the air.
  • Enveloped, helical, positive-sense, single-stranded RNA.
• Respiratory Syncytial Virus (RSV):
  • Primary entry point is the nose.
  • Replicates in the nasopharynx (back of the throat).
  • Common in children under two years old, causing mild illness but potentially more serious in young infants or immunocompromised individuals.
  • Infects the lower respiratory system and can cause ear infections.
  • Envelope, negative-sense, single-stranded RNA, non-segmented.
• Adenoviruses:
  • Cause a wide range of infections including the common cold.
  • Spread through feces, air, or close contact.
  • Non-enveloped, icosahedral, double-stranded DNA virus.

Prevention

• Frequent hand washing
• Avoid touching the eyes, nose, and mouth
• Cover coughs and sneezes
• Avoid close contact with sick individuals
• Stay home when sick