How long after you develop a flu/cold symptoms could you get a lung infection leaving the flu/cold untreated? HTN G.A.D PCOS Depressive Disorder

At any time. Bacterial infections resulting from colds which go untreated can occur at any time during the cold. Often, it's hard to say when one infection stops & another begins. Factors such as immune status, diabetes, COPD, asthma, anemia, poor nutrition, chronic fatigue, etc. can all make it easier for viral infections to complicate so as Captain Kangaroo always said, "Take Good Care of yourself."