Northland health officials are concerned that the flu virus will return next winter once the international borders open after 18 months without any cases.
There has been no influenza in Northland the past two winters, contributing to New Zealand topping the highest increased life expectancy. However, Northland DHB is bracing for its return with borders reopening next year.
The Government announced this week that fully vaccinated travellers will be allowed to enter the country from April 30 next year.
Northland DHB microbiologist Dr David Hammer said records indicated that there had been no influenza cases in Northland since around April 2020 and anecdotally it appeared numbers dropped to near zero around the rest of the country too.
"We continued to test hospital inpatients with respiratory symptoms for influenza for many months here, so the drop was not a result of detection bias. Influenza usually comes in from the Northern Hemisphere each year, although even the Northern Hemisphere has seen uncharacteristically low levels for the past two years."
Influenza is a viral infection that is introduced from overseas each year and then spreads across the country.
Epidemiologist Professor Michael Baker said the predicted return of influenza next winter, coupled with Covid-19, was a concern. New Zealand health professionals were watching the Northern Hemisphere closely as winter sets in.
He said last winter's reduced transmission of respiratory viruses reduced the country's overall mortality rate by about 5 per cent.
"About 2000 people survived who would normally have died."
He said New Zealanders gained eight months life expectancy last year, the largest increase of any country. Most countries averaged a loss of one year's life expectancy and the US and UK lost 18 months.
"We were the only country in the world who recorded an increased life expectancy because we were so good at keeping [winter viruses] out."
Baker said that influenza made up between a quarter to one third of winter deaths. Other respiratory viruses were the main problem.
"About 500 die a year from influenza in New Zealand, mostly aged over 70. But, in general, it's a more dangerous time to be old and frail and have underlying illnesses.
"The problem is we have not been exposed to influenza for a couple of years so we may well have adversities if the virus arrives in New Zealand - it's never been a better time to get the flu shot.
"I would advise getting the flu and the Covid vaccinations, certainly if [you are ] in the high-risk groups."
Hammer said although the current focus is on Covid-19, Northland DHB has plans to manage a potential increase in influenza cases in its hospitals, along with the return of respiratory syncytial virus (RSV), a highly contagious winter virus that affects babies and clogged hospitals this year.
RSV was rife across the country this past winter after a 2020 absence, peaking at 20 new cases a day in Northland, and leading to the region's hospitals experiencing some of the highest occupancy levels to date. The huge rise caused major issues across the country, clogging up emergency wards and ICUs.
Last year's absence was because of the border was closed – only a single case was detected between May and October, as opposed 529 cases for the same period this year. There are now no cases of RSV.
Hammer said the resurgence of the virus coincided with the reopening of the border with Australia and easing of lockdowns.
"We understand that Australia did not see such a drop in RSV - at least not as marked as we did in 2020."
Good hygiene practices in our communities will go a long way to protecting us from all respiratory virus infections, he added. These include hand washing, covering coughs and sneezes, staying home when sick and wearing a face mask when experiencing mild respiratory illness. Getting the flu vaccination before winter will also be very important when borders reopen.
"Another layer of protection for your child is to make sure they are up-to-date with all their immunisations. There is no vaccine for RSV but immunisation can prevent bacterial infections following RSV infection.