Tauranga residents are being urged to protect themselves for winter amid fears about a new norovirus and influenza strains emerging overseas.
Mutated strains of norovirus and influenza are expected to hit New Zealand this year, with the norovirus tipped to affect more than 100,000 New Zealanders by the time it runs its course in 2-3 years.
Both have already hit the Northern Hemisphere, with reports of influenza vaccine shortages and deaths of 20 infected children.
The H3N2 influenza strain struck early in the New York, spreading quickly to infect nearly five times as many people compared to the same time last year.
Toi Te Ora Public Health Service medical officer of health Dr Phil Shoemack said the number of people infected with the flu typically fluctuated each year.
"It doesn't mean it is any more infectious or serious than others," he said.
"It could mean we might have a worse winter than last year but this is what happens. Some years are worse than others. It's unlikely to be as bad as 2009, when we had the pandemic strain."
The National Influenza Specialist Group in New Zealand said the US flu resembled the same "Victoria" strain that struck Christchurch last year, causing nausea and hallucinations.
Dr Shoemack said older people were most vulnerable to the worst effects of the flu, which could be deadly. He recommended people took advantage of the annual flu vaccine, which was free for people 65 and over.
"What would people prefer? Being stuck in bed feeling lousy for four to five days, or a sore arm for a few hours?"
The vaccine was being processed and was expected to be approved by medical regulatory body MedSafe when it arrives in New Zealand. It includes cover against the H3N2 strain.
While the vaccine was a preventative option available to most people, Dr Shoemack said there was little that could be done about noroviruses.
"The fact is a new strain of it is unfortunate and annoying, but there is nothing we can do about it," he said.
"Norovirus is a virus unique to humans. It's very infectious and easily spread from one person to another."
This could be done through eating infected foods, being in close proximity to an infected person or skin contact.
Dr Shoemack recommended good hygiene practices to help prevent catching the bug, which is believed to have already arrived in New Zealand.
Those infected suffer 48 hours of severe illness. with APNZ