Coronaviruses not new but pandemics SARS, MERS and cousin Covid-19 more deadly

A microscope image shows the novel coronavirus SARS-CoV-2 emerging from the surface of cells. SARS is a cousin to Covid-19. Photo / US National Institutes of Health

The confirmation of a third person with coronavirus in New Zealand comes as public health officials urge calm amid panic-buying and online bullying of a Kiwi Covid-19 sufferer.

But this is not the first pandemic to arrive in New Zealand - it's not even the first coronavirus.

Severe Acute Respiratory Syndrome, or SARS, is a coronavirus that originated in southern China in 2002.

Only one person was thought to have SARS in New Zealand, but the illness killed 774 people worldwide between 2002 and 2003.

SARS was stamped out relatively quickly, infecting a total of 8096 people - mostly in China.

By comparison Covid-19 has infected 95,480, with 3285 deaths as at 3pm Thursday. At the same time, 53,688 people had recovered from the illness.

As New Zealand grapples with its first confirmed case of family transmission of Covid-19, it might help to know that coronaviruses are a large and diverse family of viruses that include the common cold and infect both humans and animals.

Covid-19's other cousin, MERS, is a coronavirus that originated in Saudi Arabia in 2012.

Middle East Respiratory Syndrome circulates each year but has not entered New Zealand.

To date it has killed 877 people globally with 2519 infected - a high death rate of 34 per cent.

In April 2009 New Zealand braced for swine flu after 10 Rangitoto College students tested positive for the influenza A virus when they returned from Mexico where it broke out.

Twenty people died of swine flu in New Zealand with 3175 cases reported.

The first death was a teenage boy with asthma in Hamilton. Globally the virus infected between 700 to 1400 million people despite a vaccine being administered in 2010.

The fatality rate was much lower than the first strain of H1N1 influenza to hit New Zealand, dubbed the Spanish flu, in 1918 to 1920.

At less than 1 per cent, swine flu killed between 150,000 and 575,000 people worldwide, while the Spanish flu - one of the world's most devastating pandemics behind the Black Death plague - had an estimated death toll of between 17 million and 50 million.

The Spanish flu, which infected about one third of the world's population at the time, was deadly to young and old.

Covid-19 instead has had more deadly effects on those with underlying medical conditions or compromised immune systems such as the elderly.

There are seven coronaviruses known to infect people. Four of them typically cause a cold and only rarely result in death.

The other three; MERS-CoV, SARS-CoV, and the new SARS-CoV-2 [Covid-19] have varying degrees of lethality.

Although the case fatality rate of Covid-19 is lower, the virus has already killed more people than the other two coronavirus outbreaks combined, which some have attributed to the pathogen's fast transmission.