The world has reached a "tipping point" in the coronavirus outbreak, an expert has warned, as fears of a global pandemic grow.

Professor Paul Hunter from the University of East Anglia said the current spread of COVID-19, the disease caused by coronavirus, outside China is "extremely concerning" and the sharp rise in cases in Italy is "a big worry for Europe".

Here, Sky News looks at why experts fear a coronavirus pandemic and what authorities are doing to try to stop it.

What is a pandemic?

According to the World Health Organisation (WHO) website, a pandemic is defined as the worldwide spread of a new disease. It can also refer to a disease which is prevalent over a whole country.


The WHO says it will not declare a pandemic as it no longer uses this as an official term with new virus outbreaks - but COVID-19 remains an international emergency.

"We could start describing it as a pandemic, but at the moment we are saying it is clusters and outbreaks in some countries," a WHO spokeswoman said.

In 2009, the H1N1 swine flu outbreak was declared a pandemic but it turned out to be mild, leading to criticism after pharmaceutical companies rushed development of vaccines and drugs.

Image: A worker in a protective suit disinfects the Dongxinzhuang village in Shandong province

How is a pandemic declared?

According to a 2017 report, the WHO has four phases to describe the outbreak of a pandemic.

Interpandemic phase - this is the period between pandemics

Alert phase - this is when a new virus has been identified and risk assessments are carried out at local, national and global levels

Pandemic phase - this is the period of global spread of the virus. Some experts say this is obviously happening with coronavirus.

Transition phase - this is when the global risk reduces and countries begin to recover

In contrast to a pandemic, an epidemic refers to the spread of illness in a "community or region...clearly in excess of normal expectancy".

Image: People in Hong Kong have formed enormous queues for protective masks

Why are we talking about a potential coronavirus pandemic?

More than 79,000 suspected and confirmed cases of COVID-19 have been identified, mostly in China where it originated, with more than 2,600 deaths.

There is now concern about the spread of the virus between people who have no link to China.

Cases in Italy have soared within a few days and the country now has the largest number of cases in Europe, at more than 200.

Fears are growing that unless the outbreak of the virus is contained within Italy, there could be more rapid spread in other European countries.

Meanwhile, South Korea reported another large jump in new coronavirus cases on Monday, a day after its president called for "unprecedented, powerful" steps to combat the outbreak.

The 231 new cases bring South Korea's total to 833, with two more deaths raising its toll to seven.

Why has coronavirus been declared a global health emergency?

The WHO has already declared the coronavirus outbreak "a public health emergency of international concern".

It is defined as "an extraordinary event" that poses a public health risk through the international spread of disease which could require an international response.

The WHO's declaration on 30 January was considered a call to action and a "last resort" measure, suggesting a situation that is "serious, sudden, unusual or unexpected" which may need an immediate response.

However, the virus has continued to spread since then.

Image: People line up outside a drugstore to buy masks in Shanghai

How many global health emergencies have there been?

Since 2009, there have been five:

The 2009 swine flu pandemic

The 2014 polio declaration

The 2014 outbreak of ebola in West Africa

The 2015-16 Zika virus epidemic

The Kivu ebola epidemic as of July 2019

Any new subtype of human influenza is automatically declared a global health emergency - such as SARS (Severe Acute Respiratory Syndrome), smallpox, and wild type poliomyelitis.

What happens after a global health emergency is declared?

The declaration triggered recommendations to all countries aimed at preventing or reducing the spread of the virus, while avoiding unnecessary interference with trade and travel.

The WHO said its greatest concern is the potential for the virus to spread to countries with weaker health systems, who may not be able to contain it.

WHO chief: We don't know what damage virus could do

"We are all in this together and we can only stop it together," said Mr Ghebreyesus.

Didier Houssin, chairman of the emergency committee, said it would hold countries to account over extra measures they may take.

Although the organisation has no legal authority, it can ask governments to provide scientific justification for any trade or travel restrictions.

Is this like SARS?

Both COVID-19 and SARS are diseases caused by types of coronavirus which originated in China and virologists say they are genetically close.

More than 2,600 people have died from COVID-19, compared to 774 killed during the 2003 SARS outbreak.

However, the fatality rate is lower for COVID-19 (at about 3%), compared to the fatality rate for SARS which was 9.6%.

Where has it spread so far?

More than 79,000 suspected and confirmed cases of COVID-19 have been identified across more than 30 countries and territories.

The vast majority of cases - more than 77,000 - are in China, followed by about 830 cases in South Korea.

Italy has seen Europe's biggest outbreak, with more than 150 cases identified and five people killed.

More than 2,600 people have died, mainly in China's Hubei province, the epicentre of the outbreak.

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What are authorities doing?

Around 60 million people are under lockdown in China's Hubei province - of which Wuhan is the capital.

Wuhan's local transport networks - including bus, subway and ferries - have been suspended and airport and train stations closed.

A number of foreign governments - including the UK - have flown their citizens out of Wuhan and advised against non-essential travel to China.

About a dozen towns in Italy are in lockdown as authorities race to contain the biggest outbreak of coronavirus in Europe.