The World Health Organization has labeled COVID-19 a global pandemic, the highest-level health emergency the organization can declare.

By calling it pandemic, the WHO hopes it will spur countries to take more action to stem the disease.

A pandemic defines a geographic area, not the medical severity of a disease.

For example, the 2014-2016 Ebola epidemic had up to a 90% death rate, and the 2015-2016 Zika epidemic affected more than 700,000 people, but neither were categorized as a pandemic by the WHO.

The new designation expands on the WHO's declaration in January that COVID-19 was a Public Health Emergency of International Concern (PHEIC).

"WHO has been assessing this outbreak around the clock, and we're deeply concerned both by the alarming levels of spread and severity, and by the alarming levels of inaction," said WHO director-general Tedros Adhanom Ghebreyesu.

Regarding which countries have not acted sufficiently Michael J. Ryan, Executive Director of WHO Health Emergencies Programme said: "You know who you are."

When asked by the Financial Times which countries he was referring to, Ryan said the WHO doesn't call out member countries in public.

The most recent pandemic was the 2009-2010 H1N1 virus that was estimated to have killed 100,000-400,000 people in the first year alone, according to the WHO.

Previous pandemics include the 1968 "Hong Kong Flu" and the 1957-1958 "Asian Flu" which caused 1–4 million deaths each. 

The 1918-1919 "Spanish Flu" was estimated to have caused 20–50 million deaths.