This is the difference between a pandemic and an epidemic WHO upgrades Covid-19 outbreak

The World Health Organisation (WHO) declared the novel coronavirus strain Covid-19 a pandemic on March 11.

"We have called every day for countries to take urgent and aggressive action. We have rung the alarm bell loud and clear," said Tedros Adhanom Ghebreyesus, the WHO chief.

"All countries can still change the course of this pandemic. If countries detect, test, treat, isolate, trace and mobilise their people in the response," he said.

"We are deeply concerned by the alarming levels of spread and severity and by the alarming levels of inaction."

Here's what the difference between an epidemic and a pandemic is.

What is a pandemic?

The WHO defines a pandemic as the worldwide spread of a new disease, across several countries or continents, affecting a large number of people.