A second child is in Whangarei hospital with meningococcal disease.
The one-year-old was admitted on Wednesday night and is in a stable condition on Thursday.
Northland Medical Officer of Health Claire Mills says it is extremely fortunate that the baby's parents sought medical help quickly.
The case is the second in Northland in days. A toddler admitted earlier this week was also found to have meningococcal infection.
Dr Mills says there is no obvious link between the cases.
She says public health staff are offering advice and preventative treatment to those who have had close contact with the baby over the past week, sharing food and drink, or playing and sleeping in the same house.