Pandemic: what does it mean and does it matter?

When does an epidemic become a pandemic? As the novel coronavirus continues its spread across the globe, what does the designation mean to world healthcare systems as they try to rein in the deadly disease?

The World Health Organization has yet to declare the current outbreak, which originated in central China last month, a pandemic.

It has indicated however that we should prepare ourselves for one.

The WHO defines a pandemic as a situation in which "the whole world's population would likely be exposed to this infection and potentially a proportion of them fall sick," said its emergencies director Michael Ryan.

WHO chief Tedros Adhanom Ghebreyesus said that countries should be doing everything they could "to prepare for a potential pandemic".

"For the moment we are not witnessing the uncontained global spread of this virus and we are not witnessing large-scale deaths," he said on Monday.

While the number of fresh cases in mainland China has slowed slightly in recent weeks, several other countries have seen infections mushroom.

These include South Korea, which has seen more than 1,100 people infected, and Italy, with more than 300 confirmed cases.

On Tuesday Iran reported four more deaths, taking the total number of fatalities to 19 and confirmed infections to 139.

"What we see are epidemics in different parts of the world, affecting countries in different ways and requiring a tailored response," said Tedros.

The WHO has not updated its designation of the outbreak since January 30, when it classed it as "a public health emergency of international concern".

Under its old warning system, which had six stages of alert, the WHO could simply start referring to coronavirus as a pandemic, which comes from the Ancient Greek for "pan demos": all people.

"Definitions and terminology aside, our advice remains the same," said WHO spokesman Tarik Jasarevic.

For Bharat Pankhania, of the University of Exeter Medical School in England, coronavirus is already a pandemic "in all but name".

"It's only a matter of time before the World Health Organisation starts to use the term in its communications," he said.

David Heymann, professor of Infectious Disease Epidemiology at London School of Hygiene & Tropical Medicine said the terminology risked being a distraction.

"What is necessary is to understand the current situation in each country," he said.

Tedros did hint that designating the outbreak a pandemic prematurely might do more harm than good.

"Using the word pandemic now does not fit the facts, but it may certainly cause fear. This is not the time to focus on what word we use," he said.

He added that even if a pandemic is declared, the world alone "will not prevent a single infection today or save a single life today."