An infant is in Royal Darwin Hospital in a critical condition with meningococcal disease.
It brings the total number of meningococcal infections for the Northern Territory this year to five, with the last four cases all being the W strain.
The strain of the current case is still being confirmed.
Those cases occurred in both the Top End and Central Australia and in both adults and children and were not connected, a Department of Health statement said.
All close contacts of the child had been contacted and provided with clearance antibiotics to prevent further transmission of the infection, the department said.
Darwin woman Mary-Ellen Hurley, 34, died from meningococcal disease on New Year's Eve hours after presenting at Palmerston hospital's emergency department.
The Centre for Disease Control acting director Dr Rosalind Webby urged people to be vaccinated against meningococcal disease.
The meningococcal ACWY vaccine is available free for all people aged 1-19 years in the NT.
