The WA Department of Health says it is the 16th case this year and the person is still recovering in hospital.
Meanwhile, the patient's closest contacts have been informed and some have been given antibiotics to minimise the chance of the organism spreading.
Meningococcal disease is an uncommon, life-threatening illness caused by a bacterial infection of the blood or membranes that line the spinal cord and brain.
The bacterium are often carried harmlessly in the back of the nose and throat by many people, and very rarely invade the bloodstream and cause serious infections.
It can spread from the nose and throat when coughing or sneezing but is not spread by saliva and does not survive more than a few seconds in the environment.
Symptoms may include a fever, chills, headaches, neck stiffness, nausea and vomiting, drowsiness, confusion, severe muscle and joint pain, and sometimes a rash.
The infection can progress very rapidly, but most people make a full recovery with appropriate treatment.
The department said the incidence of meningococcal disease had decreased significantly in WA over the past decade, with about 20 to 25 cases reported each year.
That figure is down from a peak of 86 cases in 2000.
There were 19 cases notified in 2012, the lowest number recorded in more than 20 years.
A vaccine to protect against the C type of meningococcal disease, which in the past was responsible for about 15 per cent of cases in WA, is provided free to one-year-old children.