Q.Common cold—the most infectious human ailment is caused by

The common cold is among the most frequent of all human infections, caused predominantly by rhinoviruses that infect the mucous membrane lining the nose and upper respiratory passages.

Symptoms. Infection produces nasal congestion and a runny or watery nasal discharge, repeated sneezing, a mild sore throat, and sometimes a low-grade fever; unlike pneumonia, the infection stays largely confined to the upper respiratory tract and typically resolves on its own within a few days without serious complication.

Transmission and prophylaxis. The cold spreads readily by droplet infection (through coughing and sneezing) and by contact with surfaces or hands contaminated with the virus. Because there is no specific cure, prevention is the main defence: avoiding close contact with infected individuals, practising good personal hygiene such as frequent hand-washing, and covering the nose and mouth while coughing or sneezing to limit the spread of infectious droplets to others.

Exam-focused takeaway: remember the causative agent (rhinovirus), the site of infection (nasal/upper-respiratory mucous membrane, distinguishing it from lower-respiratory pneumonia), and that prevention is centred on hygiene and limiting droplet spread rather than any drug treatment, since it is a self-limiting viral illness. …