CNN  — 

Today, March 11, marks one year since the World Health Organization declared Covid-19, the disease caused by the novel coronavirus, a pandemic.

In the first months of 2020, as the unprecedented health crisis rapidly crossed borders – China, Italy, Spain, South Korea, Japan and soon, the United States – it started to take the shape of a looming, global threat. Something beyond an epidemic.

As I researched, I was surprised to learn that there was no universally agreed-upon definition of “pandemic.” But an increasing number of medical experts and public health officials I spoke with were telling me that the rapidly unfolding situation fit the bill.

Loosely speaking, a pandemic is an outbreak of a virus that can cause illness or death, where there is sustained person-to-person transmission of that virus, and evidence of its spread in different geographic locations. Check, check and check.

Still, to call it a pandemic felt momentous and weighty. It was not a decision CNN (or I, personally) took lightly – we didn’t want to panic people – be we felt we had to call it what it was. And so we did that on March 9.

A couple of days later, WHO adopted the same language.

To be fair, WHO had been sounding the alarm steadily for nearly six weeks, since January 30, 2020, when the director general, Tedros Adhanom Ghebreyesus, declared the situation a “public health emergency of international concern” – the highest level of health alert under international law. The definition is “an extraordinary event that may constitute a public health risk to other countries through international spread of disease and may require an international coordinated response.”

For this symbolic anniversary, I spoke to Maria Van Kerkhove, WHO’s technical lead for the coronavirus response, to reflect on the year of the pandemic and beyond.

Different countries, different responses, different outcomes

Van Kerkhove – who said WHO tries to do for the world what the US Centers for Disease Control and Prevention does for the US – told me the goal of a public health emergency of international concern is to raise the alarm before you’re in an actual pandemic, when there’s still time to possibly prevent and, at any rate, prepare for what is to come. Similarly, for more than a year now, WHO has been trying to change the trajectory of the pandemic through, among other things, expertise, guidance, advice and support as well as frequent news conferences.