Rhinoviruses, the primary cause of the common cold, spread more effectively during cold weather due to several factors:

1. Cooler Temperatures Improve Virus Stability

• Rhinoviruses are more stable and survive longer in cooler, drier environments.
• Cold air helps maintain the virus’s outer protein coat, allowing it to remain infectious for longer periods.

2. Reduced Immune Response in Cooler Conditions

• Cold air can lower the temperature inside the nasal cavity, which may weaken the local immune defenses.
• A cooler nasal environment reduces the effectiveness of the mucosal barrier and decreases the activity of immune cells, making it easier for the virus to replicate.

3. Dry Air Dries Out Mucus Membranes

• Cold weather is often accompanied by low humidity, which dries out the protective mucus layer in the nasal passages.
• Drier nasal passages are less effective at trapping and flushing out pathogens, increasing susceptibility to infection.

4. Increased Indoor Time and Close Contact

• During colder weather, people tend to spend more time indoors in close quarters, which increases the chance of person-to-person transmission.
• Poor ventilation and proximity make it easier for airborne droplets containing the virus to spread.

5. Reduced Ventilation Indoors

• Cold weather often results in closed windows and reduced airflow, creating an environment where viruses can accumulate and spread more easily.

These combined factors contribute to the increased spread of rhinovirus and other respiratory infections during colder months.