How long you stay with a patient with tuberculosis will be infected depends on the infectiousness of the patient and the close contact with the patient. If the patient is highly contagious and has been in close contact with the patient, and if you inhale the TB bacteria exhaled by the patient, you are likely to become infected. This time may be one minute, or even less. However, if the patient is not obviously infectious or is very weakly infectious and is far away, such as 1m away, the risk is low and infection is unlikely. Not all patients with TB are infectious. 70% of patients with active TB are not infectious and 30% are infectious.