Why does upper respiratory tract infection occur?

Common causes of upper respiratory tract infections include viral infections, bacterial infections, reduced immunity, environmental irritants, and damage to the respiratory mucosa. These infections typically result from an imbalance between pathogen invasion and the body's immune defenses. If symptoms such as persistent high fever, difficulty breathing, or lack of improvement within one week occur, prompt medical attention is recommended.

1. Viral infection: Most upper respiratory infections are caused by viruses, commonly including influenza virus, rhinovirus, and coronavirus. These viruses spread via droplets or direct contact, invade the respiratory mucosa, replicate, and trigger inflammatory responses.

2. Bacterial infection: A smaller number of cases are caused by bacteria, such as group A hemolytic streptococcus and Streptococcus pneumoniae. Bacterial infections often occur secondarily after a viral infection, invading areas like the throat and nasal cavity, thereby worsening inflammatory symptoms.

3. Reduced immunity: Factors such as excessive fatigue, malnutrition, and exposure to cold can weaken the immune system, reducing resistance to pathogens and increasing susceptibility to infection—particularly among vulnerable populations like the elderly and children.

4. Environmental irritants: Cold air, dry environments, dust, smoke, and harmful gases can irritate the respiratory mucosa, compromising its protective barrier and creating favorable conditions for pathogen invasion.

5. Respiratory mucosal damage: Pre-existing respiratory conditions or frequent overuse of the voice may damage the mucosa, impairing its defensive function and making it easier for pathogens to adhere and multiply, leading to infection.

Treatment is primarily symptomatic. Fever and headache can be managed with antipyretic and analgesic medications, while cough and phlegm require cough suppressants and expectorants. Supportive care includes ensuring adequate rest, drinking plenty of warm water, maintaining a light diet, keeping indoor air well-ventilated, and avoiding spicy, irritating foods and physical exertion to promote recovery.