Scientists say that the "super-strain" of meningococcal disease, which suffered six lives this year, could become the dominant form in New Zealand if the rate follows overseas trends.
The Institute of Environmental Sciences and Research (ESR) began to report every week on the Meningococcal Menopause Group (MenW) after the number of cases rose from five in 2016 to 24 years for the year.
Doctors and emergency departments were asked to closely monitor possible symptoms.
The deaths include Whangarei's seven-year-old Alexis Albert, whose dear mother has applied for a national vaccination and awareness program, and Kerikeri, 16-year-old Dion Hodder, who died in Auckland City Hospital shortly after a sickness on the island of Motutap, a youth camp.
Meningococcal disease is a bacterial infection that causes meningitis – an infection of the membrane that covers the brain – and septicemia or poisoning with blood.
While Meningococcus B (MenB) has long been the predominant strain in New Zealand, causing two-thirds of cases of disease, there has been growing concern about the rise of MenW.
The share of MenB cases decreased from 67 percent in 2017 to 49 percent compared to the year, while MenW rates rose from 11 percent to 28 percent.
Dr Jill Sherwood, Public Health Doctor of the ESA, said that the increase over the past two years was "significantly higher" than the average annual notification for 2012-2015, when only 2.5 cases were reported.
Sev was particularly alarming because it was more difficult to diagnose, he was much more virulent and was involved in higher mortality rates – potentially up to 15 percent of cases.
It also affected the wider age group, with more than 40 percent of cases involving adults over 40 years of age.
It was reliably possible that New Zealand could follow trends in other countries, such as Australia, where in 2016 MenW became the dominant fear.
"Although the number of MenW cases in New Zealand is still relatively low, there is a growing trend in applications and a recent change in the order similar to the United Kingdom, Australia and Canada."
If or when MenW overtook MenB, it was difficult to predict, as there were few cases, Sherwood said.
The ESA monitored the meningococcal disease by searching for patterns based on basic demographics, such as age, gender, ethnicity, location, lifestyles, and start dates.
"For meningococcal disease, we also review the group and type of radiation and how many cases with the same strain and group that are not known to have close contact with each other, have appeared within certain populations in the last three months."
In the early 2000s, the government developed a vaccination program across the country following an outbreak program, but has since been eliminated from the vaccination plan.
However, the government has now been thinking about public funding of vaccinations against new meningococcal disease – including MenW.
Director of the immunization counseling center, associate professor Nikki Turner, said that New Zealand had vaccines for some high-risk groups that could be bought but were not on the national schedule.
"I am aware that our bodies are and continue to advocate the introduction of these vaccines to New Zealand," Turner said.
"This is a bit complicated and many factors have to be weighed."
Turner warned that vaccines, although effective, did not provide lifelong protection.
"The disease occurs mainly in infants, younger children and adolescents, and the organism is usually carried mostly into the throat of adolescents, but not exclusively," she said.
"Plans that focus on these two periods are probably the most effective. In the infant vaccine we already have a lot of vaccines, so it can be added to others, but it's not easy.
"Adolescents are probably in need of a dose, and we currently have an overview of the vaccine in a secondary school, rather than a secondary school, which may be a better age in order to get more risk for late adolescents before the vaccine is effective."
Another complicated problem was the role of a "herd of immunity" – in which immune residents could help protect something that is not.
"If you make a campaign for all young people, we may be able to reduce the transport of the organism in the throat of people and thus prevent more disease before introducing the vaccine in the schedule."
New Zealand was not the only country that struggled with how best to cope with the disease, she said.
"I believe that there is definitely the role of vaccines here, but unfortunately they will not be a magic bullet."
The share of W of all cases of meningococcal disease this year – six are fatal – more than 11% last year.
49 percent: The share of the dominant group B in the cases this year, compared to 67% last year.
15 percent: Possible share of MenW cases that are deadly.
40 percent: At least four in 10 cases include patients over the age of 40 years.