According to the chapter, what is stated about "are usually mild and" in Fitness And Wellness?
Some people become infected but don't develop any symptoms and dont't feel unwell.
These symptoms are usually mild and begin gradually.
When children exercise, their fitness needs are met, and build up energy to learn and achieve.
Some patients may have aches and pains, nasal congestion, runny nose, sore throat or diarrhea.