The viral factors include the rate of infection, the speed of the replication, mode of transmission and more. It changes with the mutation of the virus.
On other hand, host factors take age, gender, medications, diet, exercise, health and stress into consideration.
Therefore, when it comes to signs and symptoms of a particular virus, ample data needs to be collected from individuals to ascertain the most common out of the many.
Since the Delta variant is a mutation of the original strain, it is said that the symptoms may also have altered during the course of mutation. According to a self-reporting system through a mobile app, data from the United Kingdom suggest the most common COVID symptoms may have changed from the original COVID symptoms.