The World Health Organisation (WHO) says the outbreak of the coronavirus or Covid-19 is not yet a pandemic. The UN health agency’s definition of a pandemic is the spread of a disease that meets these criteria: the infection has to be widespread, over several countries or continents, considered out of control, and affecting a large number of people.
 Lines of infection are usually self-sustaining. Most cases of Covid-19 can be traced back to China. That’s where the disease was first discovered. But if there were an increase in cases in the United States and Middle East, with no clear link back to China, that would be “self-sustaining” and fit the definition of a pandemic.
 The last time the WHO declared a pandemic was for the H1N1 virus, also known as swine flu, in 2009. It’s infected more than 60 million people in the United States alone, and killed up to 575,000 people around the world.
 If a pandemic were to be declared, it would mean all countries would need to be on their highest alert. Governments would have to fully mobilise their health systems, be prepared for an influx of patients and ensure they have access to antiviral medication and other medical supplies.
 The biggest challenge may be encouraging people to adopt behaviour, such as staying at home if they feel sick and avoiding large crowds. Governments of affected countries may even consider applying emergency powers to try to curb the spread of the virus. But extreme measures like that come with an enormous price tag. The World Bank estimates the annual global cost of dealing with moderate to severe pandemics is about US$570 billion.
 Throughout history, the world has had to cope with a number of pandemics. The Black Death in the Middle Ages killed up to 200 million people. And the flu pandemic between 1918 and 1920 infected more than a third of the world’s population, and killed up to 50 million people, including many healthy young adults. And there have been at least six cholera pandemics, all of which originated in India. The last one, between 1910 and 1911, killed more than 800,000 people.
 Covid-19 has a long way to go before reaching those sorts of deaths. But the WHO warns that this latest epidemic has all the potential to become a pandemic, if effective measures aren’t taken now to stop its spread.