The disease could occur at any age, but was most common in children under five, she said.
Symptoms in babies and young children can include fever, irritability, sleepiness, floppiness, difficulty waking up, refusal to eat or drink, vomiting and skin rash.
Adults can have similar symptoms and may also have a stiff neck, headache and sensitivity to lights.
"It's a bacteria that lives in the throat and nose, and many of us carry it without knowing we have got it," Dr Mills said.
"Meningococcal meningitis can be treated with antibiotics, so anyone with some of these symptoms should seek medical attention without delay, as early treatment is very important."
Two one-year-old Northland babies were confirmed to have the disease earlier this month, while a 45-year-old woman with suspected meningococcal disease is awaiting lab results.
Also this month, a child died from the disease in Rotorua Hospital and one week earlier Fulton Hogan chief executive Bill Perry, 49, died suddenly in Christchurch.
Following Mr Perry's death three people - including one who was in a meeting with him - were hospitalised with the type-C strain of the disease.
- NZPA