Scientists and disease experts say the Wuhan coronavirus outbreak could soon be declared a pandemic.

The World Health Organisation last week designated the coronavirus – whose scientific name is 2019-nCoV – a "public-health emergency of international concern."

Calling the virus a pandemic would take it to a new level, however, since that term refers to a more global outbreak.

The coronavirus is "very, very transmissible, and it almost certainly is going to be a pandemic," Anthony Fauci, the director of the US's National Institute of Allergy and Infectious Diseases, told The New York Times on Sunday.

Here are criteria for a virus to be labelled a pandemic:

The WHO defines a pandemic as "the worldwide spread of a new disease."

A pandemic disease spreads across "several countries or continents, usually affecting a large number of people," according to the US Centres for Disease Control and Prevention.

A viral outbreak could be characterised as a pandemic if it is "markedly different from recently circulating strains" and if "humans have little or no immunity" to it, according to the UK's Health and Safety Executive.

A disease becomes a pandemic when it can infect many people over a large area, be transferred from person to person, and cause clinical illness, the HSE said.

An epidemic, by contrast, refers to a more localised or regional outbreak rather than a global one. That's what health agencies have so far considered the coronavirus outbreak to be.

The CDC says an epidemic is an "increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area."

Similarly, the WHO defines an epidemic as the "occurrence in a community or region of cases of an illness, specific health-related behaviour, or other health-related events clearly in excess of normal expectancy."

Thomas Frieden, a former CDC director, told The Times that it is "increasingly unlikely" that the coronavirus "can be contained."

He added: "It is therefore likely that it will spread, as flu and other organisms do, but we still don't know how far, wide, or deadly it will be."

Robert Webster, an infectious-disease expert at St. Jude Children's Research Hospital, told The Associated Press on Sunday that "it sounds and looks as if it's going to be a very highly transmissible virus."

The Wuhan coronavirus has killed at least 362 people and infected more than 17,000 other people in more than 24 countries since the first cases were reported in December.

All but one of those deaths were in China; on Saturday, a man in the Philippines became the first to die of the virus outside China.

This article was originally published by Business Insider.

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