Thanks for posting on HCM,
Normally when you get a stomach flu
or diarrhea, you get dehydrated and the degree of dehydration
depends on amount of fluid your husband loss while having the flu. Most stomach flu are caused by a virus and it is possible that the same virus responsible for your husband's flu might also have caused chest infection
(but with the absence of symptoms such as cough, rhinorrhea
, sputum, chest pain etc it will be have to tell if there is actually a chest infection). The shortness of breath
could be still as a result of dehydration and he might simply require taking in enough fluids to replace the loss one. It will also be good if your husband could consult a doctor for proper evaluation.
Hope this is useful.