The causes of viral colds in infants are mainly caused by the following: 1. Due to the infant being cold. After an infant gets cold, especially in the fall and winter seasons, the infant will have a low immune system, which in turn will cause viral invasion, resulting in a viral cold. After the occurrence of viral cold, infants will have a series of symptoms such as nasal congestion, runny nose, sneezing, and even fever. 2. caused by cross-infection. Because the infant’s resistance is relatively poor, if the father, mother and other adults who are in close contact with the infant suffer from a cold, the infant will also suffer from a viral cold by way of cross-infection.