Coronavirus: Who's most at risk in an outbreak

Health officials aren't sure if the coming winter will increase or dampen the threat of COVID-19.

While the focus at present is on containment - preventing the virus from spreading person-to-person in the community - it's believed deaths will be inevitable, should it get loose.

"The evidence so far shows people with pre-existing medical conditions or older people are at a higher risk of more severe illness or of dying," Director-General of Health Ashley Bloomfield told The AM Show on Monday.

"That only happens if they get it at the first place - as you know our effort at the moment is really designed to try and keep it out. We're still in that phase of our plan."

Should the virus get free, the elderly and those with pre-existing health conditions are most at risk. In patients aged 80 and older, the mortality rate appears to be about 15 percent. For those in their 70s it's 8 percent, 60s 3.6 percent and 50s 1.3 percent. 

For adults between 20 and 49, the mortality rate has been 0.4 percent or below, and there have been zero recorded deaths in children aged 10 or under.

"The evidence from children that have been affected overseas is they seem to have quite a mild illness," Bloomfield said.

"It doesn't seem to impact children near as much as it does adults, particularly older adults - so that's good news."

Influenza thrives in cold and dry conditions, he said, urging Kiwis to get vaccinated against this year's strains to ease the pressure on the health system should COVID-19 get loose - and for parents to ensure their kids immunisations against viral diseases like measles are up-to-date.

"I am going to give a shameless plug for vaccinating your children - because there is a whole range of serious infectious diseases... that are imminently preventable, and those are the ones that really do pose a risk to children."

Recent studies have found measles is able to wipe the immune system's memory, making it more likely you'll be infected with another disease - even one you've had before. 

"We've got to have that sort of collective action if we're going to both prevent and stop outbreaks of coronavirus in our country."

It's suspected the coronavirus might have trouble spreading in the northern hemisphere once the weather warms up, like flu does, but New Zealand is about to head into winter. 

"We don't know if that's going to be the case with coronavirus," said Bloomfield. 

Anyone who suspects they might have been exposed to COVID-19 should call Healthline on 0800 3585453.