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."
Dr Tuohy said the Ministry of Health was advising all health professionals of the particular risks influenza B poses to children and young people. It was recommending to family doctors that if they suspected a child or young person could have influenza B they should assess them and refer them to specialist care if they had any concerns about possible complications. Hospital doctors are also being informed.
"For parents it's really important that that we keep a close eye on children sick with flu-like symptoms. If children are unwell they should be kept at home from school with a parent or responsible guardian.''
The Ministry also advises that sick children should be kept warm, given paracetamol (NOT aspirin) for fever and plenty of fluids. If the child is not getting better, or gets better and then develops another fever, or is having breathing difficulties, the child should be taken to a GP.
If parents have already taken their child to a doctor and had a diagnosis of influenza, but they are concerned about their child or the child gets sicker, then parents are advised to take the child back to the doctor, as they may have developed another infection.
Dr Tuohy said the annual influenza immunisation is the best form of defence against influenza, and he strongly urged people to get immunised, particularly those who are most vulnerable and in the at-risk groups . These people are at higher risk of developing complications from an influenza infection.
Of the two influenza B strains in circulation B Shanghai is included in this year's vaccine. B Hong Kong is not in this year's vaccine but was included in last year's vaccine.
Flu vaccine is recommended and subsidised for children with certain chronic health conditions such as cystic fibrosis, congenital heart disease or who are being treated for cancer.