A currently-circulating strain of influenza has not been common in New Zealand since 1987 and means children and young people can be at particular risk of serious illness, the Ministry of Health says.
"Influenza B is reaching epidemic rates in children and young people in the North Island, with high rates of absenteeism in some schools. We now know that In the last six weeks three young people became ill with influenza B and have died from complications from the virus," Ministry spokesman Dr Pat Tuohy said.
"We are currently asking all hospitals to tell us whether they are treating children and young people with the same sorts of illnesses."
The Ministry last week advised parents and clinicians to be vigilant and warned that the current rate of influenza in New Zealand communities was higher than at the same time last year, with tests confirming influenza B viruses were dominant.
Dr Tuohy, Chief Advisor Child and Youth Health, said today that information since then had confirmed that the three deaths in young people involved complications from influenza B.
"In New Zealand we have not seen large numbers of people infected with this type of influenza (Hong Kong B) since 1987, although a few people had it in 2002. What that means is that most people born since 1987 will not have natural immunity and are hence more likely to be susceptible,'' he said.
"There are two strains of influenza B circulating at present - Hong Kong and Shanghai. The three young people who died had the Hong Kong strain."
"We have to remember that as many as 600 children and young people die each year in New Zealand and up to 10 per cent of these are from infectious diseases. However we are sufficiently concerned by these three influenza-related deaths to repeat our messages of last week and ask parents and health professionals to be extra vigilant."
"All parents, caregivers and clinicians need to be aware that the impact of Influenza B on children and adolescents can be much more severe than has previously been recognised, and to care for any young person with influenza-like symptoms with this in mind."
Dr Tuohy said it was only now being recognised internationally that Influenza B could lead to serious illness and death from a secondary infection in children.
"It now seems likely that around the world influenza B has been implicated in more deaths in children and young people than the records show. Although the cause of death may have been recorded as bacterial pneumonia or some other infection in fact it was the Influenza B which made them vulnerable to that infection."