Question

Which of the following microorganisms causes the common cold?
A. Bacteria
B. Virus
C. Protozoa
D. Algae

Answer 1

The microorganisms that cause upper respiratory tract infections (URTIs) and proliferate at the temperature lower than normal body temperature commonly found in the nose. The common cold is mainly affecting the respiratory system.

Complete answer: Rhinovirus is the most common viral infectious agent that causes the common cold. It commonly proliferates at $33 - {35^0}C$ in the nose. This is the most active virus that causes respiratory tract infections that can be mild as well as severe. It contains capsid and four viral proteins namely VP1, VP2, VP3, and VP4. It has RNA as the genetic material. It is a non-enveloped virus with an icosahedral capsid. It is commonly transmitted by aerosols and direct contact. It also causes asthma and chronic obstructive pulmonary diseases such as pneumonia, and bronchiolitis. Rhinovirus binds to a low-density cellular receptor on the airway epithelial cells to initiate its replication cycle. It belongs to the enterovirus genus in the family Picornaviridae. It has three distinct species with distinct genotypic features. It is most commonly active in summer, spring, and early fall.
Hence, the correct option is B-Virus.

Note: Rhinovirus usually causes most of the colds. It is associated with upper respiratory and lower respiratory syndromes. It is also a common cause of asthma exacerbations. It's also a cause of chronic bronchitis and pneumonia. It usually replicates in the lower respiratory tract. Many other viruses and pathogens are also related to lower respiratory tract infections.