Whangarei Hospital is dealing with another case of meningococcal disease, the 13th in the region since July.
The latest patient is a four-year-old boy admitted on Tuesday.
Nine of the Northland cases, including three people who died, have been caused by meningococcal-C, a strain of the disease that's been relatively uncommon in New Zealand till this winter.
Northland Health says the young boy is now comfortable and his condition is improving.
Public health nurses and GPs in Northland have vaccinated more than 21,000 children and young people against meningococcal disease.
The shots, which are free for anyone aged between one and 20, are available from doctors and community clinics until 16 December.