Upper respiratory tract infections in dogs are mostly caused by three major reasons. First, the surrounding living conditions are poor, lack of hygiene, lack of daily exercise, and low defense function; second, cold weather can easily cause the contraction of the nasal mucosa. Disorders can lead to infections of the dog's upper respiratory tract; third, about 90% of dog upper respiratory tract infections are caused by viruses. Bacterial infections are often secondary to viral infections and are spread through virus-containing droplets or contaminated equipment.