Should I take my 5 and half month old son shopping if theres a flu outbreak?

No. Influenza outbreaks are the leading headlines in all of the news networks. You would like to minimize your child's exposure, so keep him at home.
Planning helps. You need to live your life & if the kid needs to come along plan ahead. Early mornings on weekdays (never weekends) or late evenings can avoid the crowds. A simple infant carrier like a chest pack can keep baby facing you and give you more control over contacts. Make your list, go where you know the layout, and get out quickly. If baby can stay with dad, let him keep him or do the shopping.