In most situations three days of antibiotics is insufficient. Remember absence of symptoms is not the same as absence of disease and short courses of antibiotics may actually confer resistance to antibiotics for further use. A specialist will guide you on rationale choices, use and duration of treatment besides giving you a complete holistic picture.
You should know if in the areas that you are travelling there is a higher likelihood of infections. Some areas around the world require prophylaxis, others require vaccinations, besides other precautions.
Yes it is, though the period of maximal infectivity is maximally before the appearance of fluid filled areas called vesicles, at the peak of the infection the condition is highly communicable.
Chest infections usually follow patterns in people who have structural lung disease, environmental triggers, age besides other factors. Such patients benefit from a vaccination strategy against common pathogens besides a pulmonary rehabilitation programme.