**Question:** Common cold are caused by which virus: September 2006, March 2013 (h)

**Core Concept:** The common cold is a group of viral infections, primarily caused by rhinoviruses, which are members of the Picornaviridae family. Other viruses may also contribute to common cold symptoms, including coronaviruses, respiratory syncytial virus (RSV), and adenoviruses. The question specifically mentions the years September 2006 and March 2013 (h), which may refer to the emergence of new strains of rhinoviruses during these time periods.

**Why the Correct Answer is Right:** The common cold is primarily caused by rhinoviruses, which are among the most common viruses responsible for respiratory infections. These viruses are known to have high genetic variability and mutate frequently, leading to the emergence of new strains over time. While the years mentioned (September 2006 and March 2013) may refer to the emergence of new rhinovirus strains, the correct answer encompasses all viruses that can cause the common cold, not just those associated with the mentioned years.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect because it refers to a specific year (September 2006) without mentioning the primary cause of the common cold, which is rhinoviruses.
B. Similar to option A, option B focuses on a single year (March 2013) without addressing the primary cause of the common cold, rhinoviruses.
C. Although option C mentions several viruses, it does not specifically identify rhinoviruses as the primary cause of the common cold.
D. This option also refers to a specific year (March 2013) without adequately addressing the cause of the common cold, which is rhinoviruses.

**Clinical Pearls:**

The common cold is a highly contagious respiratory illness characterized by symptoms like nasal congestion, runny nose, cough, and sore throat. While the years September 2006 and March 2013 may have seen emergence of new rhinovirus strains, the correct answer addresses that the common cold is caused by a diverse group of viruses, including rhinoviruses, which are responsible for the majority of cold cases. These viruses are known for their high genetic variability and mutations, contributing to the emergence of new strains over time.

**Correct Answer:** Common cold viruses (e.g., rhinoviruses) are responsible for the majority of cases, despite the years mentioned (September 2006, March 2013) potentially representing the emergence of new strains.