could be the only feature of pneumonia
.it is caused by an infection in the lungs. The diagnosis will be confirmed by a good quality chest Xray - which must show a patch. In view of his age he needs to be assessed carefully to see if he can be treated as an inpatient or an out patient.There is a score known as the PORT score which can be used to decide this. also its important to know whether your father had been admitted in a hospital or visited any health care facility in the 14 days prior to his symptom onset.This is to differentiate between an community acquired pneumonia and a hospital acquired pneuminia.
whether he is at home or in the hospital he will require antibiotic therapy if there is apneumonia. please follow-up with your doctor quickly because the earlier the antibiotic is administered the better the outcome