A doctor in Australia is presented with a patient who is complaining of coughing, chest pain,

fever and fatigue. The doctor completes blood tests and chest x-ray which shows the patient

has tuberculosis (TB). After some conversation, it is discovered that the patient has recently travelled to India, and the onset of symptoms began shortly after they arrived home. According to Australian law, doctors must report TB cases to authorities.

Is this an example of active or passive surveillance? Explain your answer with reference to a

potential limitation.