Evidence is mounting that the novel coronavirus outbreak has reached a critical mass and is likely to drag on for months. Even without an outbreak, the virus will have severe consequences for New Zealand. Ben Heather reports.

It probably started with a bat infecting a domestic animal, perhaps a goat or sheep.

Weeks, perhaps years later, at a market bustling with live animals in the Chinese city of Wuhan the virus jumped from animal to human for the first time. Over the next 14 days that person developed a fever, followed by a dry cough. By then they had probably infected others.

The first cases of the novel coronavirus were detected a little over a month ago.

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By Friday afternoon more than 31,000 people had contracted that virus with more than 630 dying. Most were in Wuhan city and wider Hubei province.

DAVE ROWLAND/GETTY IMAGES Passengers arriving on flights wear protective masks at the international airport in Auckland, New Zealand.

However, outbreaks have now been reported in nearly every corner of China and cases have been reported in more than 20 other countries, from Australia to Germany.

A growing number of experts believe the coronavirus should now be classed as a global pandemic, with the number of people infected worldwide likely to be severely under-reported.

While a case hasn't yet been reported in New Zealand, the official consensus is it's probably only a matter of time.

But regardless, the outbreak is already hurting New Zealand and New Zealanders. Disruption to the Chinese economy and travel restrictions both here and there are hitting the tourism, education, forestry, agriculture and fisheries.

Thousands of New Zealanders in China – only a fraction of which were evacuated by the New Zealand Government last week – face long uncertain waits in ghost towns and cities behind containment lines as the infection spreads.

And then there's the ugly human side of the viral epidemic: The reports of racism, linking Chinese to infection, and the hocus-cures spread online.

And all this after little more than a month.

While this disease could still be abruptly curtailed or vaccine quickly discovered, this is looking less and less likely.

So what does a prolonged outbreak mean for New Zealand?

Anatomy of a virus

Whether there is a major outbreak in New Zealand, or any other country, depends primarily on how effectively the virus spreads and kills.

Variations in a virus' transmissibility and mortality are the difference between mild seasonal ailment and a global pandemic that wipes out tens of millions of people.

Early guesses suggested a person who contracts coronavirus will, on average, infect two to three other people. This would make it more contagious than most flu strains but less contagious than measles.

CDC The risk for New Zealand from the 2019 Novel Coronavirus (2019-nCoV) depends greatly on ts transmissibility and mortality, neither of which are well understood.

Another equally uncertain guess is this virus kills between two and three out of every 100 infected. That is less deadly than Sars, which was far less contagious, but much more deadly than influenza.

A paper published in Lancet has estimated major outbreaks of the coronavirus are already underway in Chineses mega cities like Shanghai and Beijing, which would soon resemble Wuhan, the viral epicentre.

As these cities are the major gateways to the rest of the world, we should expect outbreaks in places with heavy traffic like China, such as Bangkok and Seoul. Overall, the study said we should expect cases to double every six to seven days.

Professor Michael Baker, of Otago University's public health department, said the truth was that there was still "huge uncertainty" over just how contagious or deadly the virus is.

But if that Lancet paper was right the virus would be "very hard to minimise" even with most extreme quarantine measures. That made determining the mortality rate all the more important, he said.

"If there is risk of a major pandemic then we need to know what the consequences of infection are."

Auckland University associate professor Siouxsie Wiles said the next few weeks would be crucial.

"China has gone to unprecedented length to stop this organism. The question is how well that has worked."

If cases continue to grow exponentially despite China's best efforts that bodes ill for the rest of us.

Containing the spread, counting the cost

If the above all sounds a little apocalyptic, it is worth emphasising that New Zealand's Ministry of Health still believes an outbreak here is unlikely.

The most likely scenario, according to the Ministry, is a few people sick with the virus arrive on our shores and are quickly isolated and contained. End of story.

There is moderate chance some of these people will infect others, as has happened in some other developed countries, but that, too, should be quickly contained.

China was caught by surprise, New Zealand has been forewarned and has the advantage of no land borders. If the virus spreads elsewhere across the globe we can block inbound travel, as we already have with visitors from mainland China.

But even if we avoid an outbreak in New Zealand, coronavirus is already costing us.

Tourism Industry Aotearoa has estimated the ban on foreigners' arrivals coming from mainland China, imposed last Sunday, will cost the industry $94m over a fortnight.

DASHA KUPRIENKO/STUFF Tourism centres like Queenstown (pictured) rely heavily on Chinese tourists.

Chinese international students hoping to return to New Zealand after the summer break in China are also now stuck thousand of kilometres away from their university, barred from entering the country.

According to one analysis earlier this week the export of tourism and education to China generated almost $3.5 billion last year, or just over one per cent of GDP.

The disruption within China is also hitting the export of Kiwi goods.

Forestry crews have stopped work because there are not enough people working in Chinese ports to process the logs. Crayfish destined for Chinese consumers may be returned to the sea and cool stores are running out of room to keep export meat destined for China. Even global milk prices have been hit.

Economist Michael Reddell said the travel restrictions to prevent illness and death from the virus in New Zealand had already resulted in "a pretty significant, out of the blue shock" to the economy.

Westpac estimated on Monday that if New Zealand's current travel ban persists for two months, it will shrink the economy by 0.04 per cent for the first quarter of the year. However, given what we know about the virus, it could easily persist in April and beyond and travel restrictions could tighten further.

Reddell said if the outbreak drags on overseas, industries' ability to deal with short term shock with be stretched to breaking point. Tourism businesses and universities would be devastated.

"There would lay-offs, business confidence would take a big hit."

If China's economy slowed sharply in response to the outbreak, the world could slump into recession, he said, compounding New Zealand's woes.

Outbreak here

That's the likely cost to New Zealand if we keep the virus out.

What if we don't?

New Zealanders stuck in mainland China can give us a clue. Those who have spoken to Stuff over the past fortnight have described major cities virtually deserted but for security guards checking people's temperature.

They have spoken of shops and public transport closed and shortages of essentials, like petrol and baby's nappies.

Movement between neighbouring villages is severely restricted in much of the country, travel back to New Zealand nigh impossible.

The Ministry of Health's pandemic plan includes steps that sound remarkably similar.

If there are widespread outbreaks across New Zealand, options include closing schools, preventing all travel in and out of the country, banning public gatherings, preventing the movement of goods and people in and out of infected regions, and compulsory isolation of "at-risk" populations.

DAVID WHITE/STUFF The coronavirus quarantine centre, north of Auckland, for Kiwis coming back from Wuhan. New Zealand's pandemic plan makes provision for containment centres like this to be set-up through the country.

Professor Nick Wilson, of Otago University's public health department, said New Zealand's sparser population could help slow the spread, but it could still be devastating.

"It will have a huge impact on the health system. It doesn't take much to overload our intensive care units."

Reddell believes a major pandemic could knock as much as 20 per cent off New Zealand's GDP. Bars, hotels and restaurants would close, many people would lose jobs or stay at home.

"The housing market would seize up, economic activity would largely grind to a halt."

How it ends

Because the new coronavirus remains an unknown quality, it is impossible to say where it will end.

But there are a few possible scenarios.

The most positive is that a vaccine is developed rapidly and mass jabs halt the virus quickly. Wilson said vaccines had been previously developed in as little as three months and rolled out quickly thereafter. That could eradicate the virus within a few months, allowing the world, and New Zealand, to resume business as usual.

Reddell said economies usually bounced back quickly once diseases were contained, and may even get a boost from pent up demand.

However, even if a vaccine is developed it will likely take longer than a few months. In the meantime the virus would continue to spread.

Another possible scenario is that global containment measures work and the virus fizzles out by itself quickly, much like the 2003 Sars outbreak. This is still possible. Wilson says thus far more developed countries have managed to prevent any major outbreaks outside China.

But many more people have already been infected with this new virus than Sars and early signs are that it is more contagious. This means infection could linger well into the second-half of 2020, along with the economically damaging travel restrictions in New Zealand.

A third scenario is the virus is truly globally devastating, on par with, or worse than, the 1918 influenza pandemic. That outbreak killed 50 million people worldwide, including about 9000 people in New Zealand – about one per cent of the population at the time.

Baker said if this virus was as deadly as early guesses suggested, and the rapid spread continues globally, this scenario became more likely.

"If it is going to infect a high proportion of the world you get very concerned if it is killing anything above one in 10,000."

A final possibility is that the virus does spread far and wide but, in the process, becomes more benign. Baker said that over time viruses tend to get less deadly and more contiguous.

If this happens, coronavirus will become more like the seasonal flu, something to be endured rather than eradicated. Over time New Zealanders will build up a resistance and coronavirus jabs will become a yearly ritual.

Flu still kills about 400 New Zealanders a year, but its doesn't cause widespread disruption to trade and travel.

We have learnt to live with it.

We may have to do the same with coronavirus.