What are the causes of frequent viral colds?

Viral influenza is primarily caused by pathological factors and triggering factors. Viral influenza is a systemic disease affecting the upper respiratory tract due to various viral infections, whereas the common cold is an upper respiratory infection caused specifically by respiratory viruses.

I. Pathological Factors

1. Viruses

Viruses are the most common cause, accounting for over 90% of influenza infections. Common viruses include: rhinovirus, which accounts for about 50% of cases; coronaviruses (15–20%); adenoviruses (10%); Coxsackievirus, Echovirus, and other enteroviruses (10%); and respiratory syncytial virus (5–10%).

2. Bacteria

Bacterial infections are most commonly caused by hemolytic streptococcus, followed by Staphylococcus, Haemophilus influenzae, Streptococcus pneumoniae, and others.

3. Reduced bodily defenses

Individuals with poor nutrition or lack of regular physical exercise are more susceptible to viral influenza.

II. Triggering Factors

1. Sudden drop in temperature

Cold air weakens the nasal mucosa's resistance to pathogens, significantly increasing the risk of illness.

2. Air pollution

Polluted air not only damages the respiratory tract mucosa and impairs the upper respiratory system, but also reduces ground-level ultraviolet radiation, enhancing the activity of airborne pathogens and contributing to influenza outbreaks.

3. Enclosed environments

Poor air circulation promotes the growth and spread of pathogens, which, when inhaled, can lead to viral influenza.

4. Excessive fatigue

Overwork and sleep deprivation reduce local defensive functions of the respiratory tract, allowing pre-existing viruses or bacteria to rapidly multiply and trigger viral influenza.