Tuberculosis Consultant Services

If a person develops tuberculosis, it cannot usually be known when the individual concerned had become infected with M tuberculosis as the incubation period of tuberculosis is not constrained into a defined maximum.

In this pre-chemotherapy era study on the sparsely populated Faroe Islands, the minimum incubation period could be determined by observing children from villages which had not had a case of tuberculosis since the child's birth. Children who visited a relative with untreated tuberculosis in a different village for a defined period of time (24 hours, a weekend, a few days) and then returned to their village were observed for signs and symptoms of primary tuberculosis (initial fever, erythema nodosum, etc). In those who had been exposed for just one day (red circles), the incubation period could be determined to the exact day, while those exposed for more days, infection could have been acquired at the maximum on the first, and at the minimum on the last day of the visit providing possible exposure. From this series, the median minimum incubation period was determined to be just above 40 days or 6 weeks.