Meningococcal disease appears to be on the rise in WA again after a fifth case was notified to authorities in a month.
The Health Department said an elderly person was recovering in hospital after being diagnosed with serogroup Y meningococcal disease.
The incidence had been decreasing dramatically in WA over time, from a peak of 86 cases in 2000, down to 16 in 2013.
But last year 23 cases were reported in WA, and there have been 15 so far in 2017.
Departmental medical coordinator Professor Paul Effler said the increase was likely due to people developing an immunity to certain strains.
"I think it's in part to the mutations that happened, the changes that happened in the bacterium itself, people develop immunity to it, and we develop immunity across the population so it goes away and then it comes back if a new strain that we haven't been exposed to comes into the community," he said.
"The other thing that occurred is we started doing vaccinations against meningococcal C some years ago and that's helped drive down C to record low levels."
Vaccinations urged
Professor Effler said outcomes were similar for all strains of the disease.
He said a vaccination campaign had been launched for adolescents aged 15 to 19 after an increase in cases of the W strain.
Teenagers in this group had the highest rates of carriage of the bacteria in the back of the nose and throat, and were believed most likely to be responsible for transmission to children and the elderly.
"Uptake is good but we'd encourage any parents, or parents of teens, or teens that are out there in those years to make sure they look for their consent form that'll be coming home from the school so they can get their vaccination for free at school," he said.
