The Covid pandemic may never be over, but the public health threat should continue to decline

“It’s with great hope that I declare Covid-19 over as a global health emergency,” WHO director general Tedros Adhanom Ghebreyesus said last week. “That does not mean Covid-19 is over as a global health threat.”

The pandemic, which was first declared a public health crisis of international concern by the World Health Organisation (WHO) on January 30th, 2020, resulted in unprecedented lockdowns, economic upheaval and the deaths of at least seven million people worldwide. But the death toll is likely much higher than reported, and the WHO estimates it could be more than 20 million globally.

So is the pandemic over or not?

No it is not, but don’t expect the WHO to be the ones to announce it when it is. The hidebound organisation does not declare the beginning or end of pandemics, although it did start using the term for Covid in March 2020.

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But in a nod to the inevitable questions about the pandemic ending, Dr Mike Ryan, director of the WHO’s health emergencies programme, said the emergency may have ended, but the threat is still there. “We fully expect that this virus will continue to transmit and this is the history of pandemics,” he said. ”It took decades for the final throes of the pandemic [influenza] virus of 1918 to disappear.

“In most cases, pandemics truly end when the next pandemic begins.”

Probably the best indicator that the pandemic is far from over is that there were nearly three million cases and more than 17,000 deaths from the disease reported globally in April.

Why is it so difficult to say, with certainty, when a pandemic is over? A look at the scientific definitions of “epidemic”, “pandemic” and “endemic” may help.

An epidemic involves an increase in the number of cases of illness, but is limited to a specific geographic area – that area could be as small as a single town and as large as a country.

In a pandemic, there’s an exponential increase in cases occurring in multiple places around the globe. There have been many pandemics throughout our history, including in the recent past. The 2009 outbreak of H1N1 – also known as swine flu – was a pandemic. It caused more than 280,000 deaths worldwide in a single year.

An infection is endemic if the case numbers stay relatively consistent over time and the illness stays localised to a specific place. For example, malaria is endemic in India.

It’s far easier to know if an epidemic has ended than it is to call the end of a pandemic. Why? Because all the epidemiological data is concentrated in a single place.

But do we still need to take Covid-19 precautions? For most people many of the measures seen at the height of the pandemic, such as mask-wearing and social distancing, are no longer needed. However, if you live with someone with a compromised immune system or other chronic health condition then mask-wearing and other precautions may be in order. Vaccination still has a role to play – if you qualify for a booster dose you should get one.

Long Covid means the pandemic is likely to have a significant long-term tail to it. Long Covid is not only not going away, its prevalence is increasing. Some studies suggest one in three to five people with Covid go on to develop the longer variant of the illness.

The Covid pandemic may never be over. However, the public health threat of this virus should continue to decline. There are strong signs it is becoming a series of “wavelet” infections as new variants emerge. The latest named variant of interest is Arcturus (XBB.1.16), a sub-variant of Omicron first detected in India in January of this year, but where it is now declining.

“It ain’t over till the fat lady sings” is a sporting and operatic colloquialism. And there are certainly no sounds yet of a pandemic swan song.

mhouston@irishtimes.com