Active people who suffer acute infectious illness may have questions concerning participation in exercise or sports during their illness. Many patients are reluctant to "get behind" on their training or "let down the team." Physical activity, however, may worsen the condition, result in impaired performance, or infect others. On the other hand, some contagious diseases are relatively benign, and some activities don't affect others. Therefore, clinicians need to understand both the sport and the illness to know what level of activity to recommend. For example, solo exercise at a reduced intensity is generally safe for patients whose symptoms are above the neck.