The drop from 95 cases on Sunday comes as NT Health adjusts its virus reporting period, with only 12 hours worth of cases tallied on the first day of the new model.
Twenty of the new cases are interstate or international arrivals and 17 are close contacts of previous infections.
There are two cases of community transmission, with 19 cases under investigation to identify the source,
"A number are already suspected of being related to community transmission," an NT Health spokeswoman said in statement on Monday.
Cases have been detected in the greater Darwin area, Alice Springs, Katherine and Tennant Creek.
Two new cases in Alice Springs are known close contacts of interstate travellers.
The source of two new cases in Tennant Creek is being investigated.
There were seven new cases in Katherine, with six of these known close contacts of previous cases in the Warlpiri camp and Binjari community.
The seventh case is a Katherine Hospital staff member whose infection was discovered during routine screening.
"That person's infection was likely to have acquired their infection from a patient at the hospital," the spokeswoman said.
The reporting period change was made due to the growing number of cases in the territory and the extra work this is creating for contact tracing and testing staff.
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