Recently, a group of 92 marathon runners were placed on either a vitamin C supplement or a placebo for three weeks prior to a race. Chloroform is a by-product of chlorination and is a potent oxidant and respiratory irritant. The presence of such an oxidant increases the need for antioxidant nutrients. In such a case, we potentially have a combination of heavy training with immune suppression, environmental exposure, and increased nutritional needs. I noted above that elite swimmers are more susceptible to infection as the season progresses.
Asthmatic swimmers are similarly more susceptible to respiratory infection.
Should we follow the allopathic approach of managing the asthma with bronchial inhalants and treat each infection separately with antibiotics. Another area that affects infection susceptibility is mood, attitude, coping, and stress. So significant is this effect that an entire new field of study has emerged called psychoneuroimmunology. I think both are and equally so. In over half of respiratory illnesses, complete cultures fail to yield an etiologic agent.