Since 2017, there has been steady rise is case numbers, although this continues to be a rare disease. To date this year we have just under 100 cases nationwide and there are higher rates in some regions, particularly in Northland
We have five main serotypes groups circulating in New Zealand. Serotype B is normally about two thirds of the cases, but in the last two years, we have seen an increase in type W. To date this year W is now around 25 per cent of all cases.
This particular W strain has been seen increasing in many parts of the world, including Africa, parts of Europe and Australia.
This strain appears to be more virulent (sometimes called “hypervirulent”), and has a higher mortality rate.
While the major age groups affected continue to be infants, young children and adolescent/young adults, W is more often seen across all age groups. (NB: Over 40 per cent of cases this year were in people over 40 years.)
The other difference for this strain is it more commonly appears in more atypical fashion – of particular note is that gastrointestinal symptoms can be prominent.
Other atypical presentations include pneumonia, septic arthritis, endocarditis or epiglottitis.