Viral Diseases: Common Cold and SARS (COVID-19)

This section covers two viral diseases of the respiratory tract that differ enormously in severity — the everyday common cold, and SARS (COVID-19), a disease that became a defining global health event of recent years.

The common cold is most often caused by rhinoviruses, though several other viruses can produce a similar illness. It spreads through airborne droplets released when an infected person coughs, sneezes, or talks, and also through contact with contaminated surfaces followed by touching the nose, eyes, or mouth. The virus infects the nose and upper respiratory tract, producing familiar symptoms: nasal congestion, a runny or blocked nose, sneezing, a mild sore throat, and sometimes a mild cough. The common cold is self-limiting, meaning the body's own immune response usually clears it within about three to seven days without any specific treatment; care is supportive — rest, fluids, and steam inhalation — and prevention relies on basic hygiene such as regular hand-washing and avoiding close contact with someone who is currently infected.

SARS (COVID-19) stands for Severe Acute Respiratory Syndrome, and the specific coronavirus responsible for the pandemic that began around 2019-2020 is named SARS-CoV-2. It spreads mainly through respiratory droplets and smaller airborne particles (aerosols) released when an infected person breathes, talks, coughs, or sneezes, and can also spread through contact with contaminated surfaces. The range of illness caused by SARS-CoV-2 is wide: many infected people experience only mild symptoms such as fever, dry cough, sore throat, fatigue, and a temporary loss of smell or taste, while a smaller proportion — particularly older adults or those with certain underlying health conditions — can develop more severe breathlessness requiring hospital care. Most people who contract COVID-19 recover fully with appropriate rest, fluids, and medical care where needed. …