The World Health Organization has repeatedly stopped short of calling the coronavirus outbreak a pandemic - until today.
Speaking at a press conference today the director general, Dr Tedros Adhanom Ghebreyesus, finally used the term to describe the outbreak, which has now spread to well over 100 countries and infected over 120,000 people.
"WHO has been assessing this outbreak around the clock and we are deeply concerned both by the alarming levels of spread and severity, and by the alarming levels of inaction," Dr Tedros said.
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"We have therefore made the assessment that Covid-19 can be characterized as a pandemic. Pandemic is not a word to use lightly or carelessly," he added.
But what does this actually mean and what are the implications?
What is a pandemic?
Pandemic, a word from the Greek pan ("all") and demos ("people"), is the term used by disease experts when epidemics are growing in multiple countries and continents at the same time.
This is different to an epidemic – which is usually used to describe an outbreak that has grown out of control yet is limited to one just country or location.
But despite the fear the word evokes, "pandemic" refers to the spread of a disease, not its potency or deadliness.
According to the WHO definition, a pandemic is "an outbreak of a new pathogen that spreads easily from person to person across the globe".
This means a disease outbreak will be labelled as a pandemic when it is widespread, over several countries or continents, usually affecting a large number of people. The disease must also be infectious – cancer affects many people around the world, but it is not infectious and so is not a pandemic.
A pandemic also has self-sustaining lines of infection – which means that human to human transmission is widespread.
Until now, the WHO has stopped short of calling the outbreak a pandemic because they said that local spread was limited and most cases had a connection to China or another emerging hotspot - for instance Iran or Italy.
But it's now clear that local transmission is widespread, with over 115 countries detecting the virus and more than 10 confirming at least 500 cases.
When was the last pandemic declared?
Pandemics can vary greatly in scale and potency, but examples include HIV, swine flu and the 1918 Spanish flu. Some of the most deadly pandemics in history were the Black Death, which killed up to 200 million people in the Middle Ages, and smallpox, which killed about 300 million in the 20th century.
But the last time the WHO declared a pandemic was in 2009 for the H1N1 influenza outbreak.
At the time, the decision was criticised by some countries which felt that it caused unnecessary panic. It also led to many nations wasting money on vaccines for a strain of flu that proved to be mild and relatively easy to contain.
What is the process for announcing a pandemic?
But a lot has changed since 2009 – including WHO processes. The organisation says there is no longer a formal process to categorise an outbreak as a pandemic – instead, they announced on January 30 that the epidemic was a public health emergency.
This is the highest level classification to describe a disease outbreak under the International Health Regulations and, officially speaking, probably changed the response more than the announcement of pandemic.
A spokesperson told the Telegraph: "WHO does not use the old system of six phases – that ranged from phase one (no reports of animal influenza causing human infections) to phase six (a pandemic) – that some people may be familiar with from H1N1 in 2009.
"We do use term pandemic for all sorts of purposes and may qualify a situation as pandemic, but there would no official announcement."
So today, when Dr Tedros called the epidemic a pandemic, it was not a decision based on any formal process - although the WHO was keen to emphasise that there had been a lot of consultation with people both inside and outside the organisation.
But language matters and using the term is still a significant step.
Mike Ryan, director of emergencies at the WHO, said: "This is not a trigger for anything other than more aggressive or intense action. It's taken very seriously and we understand the implication of the word.
"The director general has gone through very complex internal and external consultation over long hours on the use of the word," he said.
Does calling the outbreak a pandemic change anything?
Even though though it is not an official process using the term that could still have serious consequences.
According to WHO's pandemic preparedness plan, a response to a pandemic would require national governments to action the "full mobilisation of health systems, facilities, and workers at national and subnational levels", to "distribute personal protective equipment" and to "distribute antivirals and other medical supplies in accordance with national plans".
Dr Tedros also said he used the term because he was alarmed at "levels of inaction" around the globe – so it's likely that he wanted to force nations to take further action to contain the coronavirus.
"WHO has been assessing this outbreak around the clock and we are deeply concerned both by the alarming levels of spread and severity, and by the alarming levels of inaction," he said.
"Describing the situation as a pandemic does not change WHO's assessment of the threat posed by this coronavirus. It doesn't change what WHO is doing, and it doesn't change what countries should do."
Dr Tedros then reiterated advice on how governments should prepare for and respond to the disease:
"I remind all countries that we are calling on you to: activate and scale up your emergency response mechanisms; communicate with your people about the risks and how they can protect themselves; find, isolate, test and treat every Covid-19 case and trace every contact; ready your hospitals; protect and train your health workers.
"Let's all look out for each other," he said.
What's the economic impact of a pandemic?
According to the World Bank, the annual global cost of moderate to severe pandemics is about $570 billion (about £440 billion) or 0.7 per cent of the world's income.
The Sars outbreak in 2002-03 – which only infected about 8,000 people – caused about $50 billion in damage to the global economy. Although its mortality rate is lower, the coronavirus could be even more destructive.
This is partly because of the world's greater reliance on China than 17 years ago. China represented just five per cent of the world economy during Sars – now it accounts for a fifth, and about a third of global growth.
Already in the last week - and before the outbreak was labelled a pandemic - the global economy has taken a huge hit, with oil prices falling and one of the worst days for the stock market since the financial crash.
How do you stop a pandemic?
Just because the outbreak has been labelled a pandemic does not mean it cannot be contained.
Dr Tedros said: "We have never before seen a pandemic sparked by a coronavirus. And we have never before seen a pandemic that can be controlled at the same time.
"We're in this together, to do the right things with calm and protect the citizens of the world. It's doable."