COVID-19: endemic doesn't mean harmless - Nature.com

To an epidemiologist, an endemic infection is one in which overall rates are static — not rising, not falling.

In other words, a disease can be endemic and both widespread and deadly.

Stating that an infection will become endemic says nothing about how long it might take to reach stasis, what the case rates, morbidity levels or death rates will be or, crucially, how much of a population — and which sectors — will be susceptible.

Soon after the Alpha variant emerged and spread in late 2020, I argued that, unless infections were suppressed, viral evolution would be fast and unpredictable, with the emergence of more variants with different and potentially more-dangerous biological characteristics.

The same virus can cause endemic, epidemic or pandemic infections: it depends on the interplay of a population’s behaviour, demographic structure, susceptibility and immunity, plus whether viral variants emerge.

Even if one region reaches an equilibrium — be that of low or high disease and death — that might be disturbed when a new variant with new characteristics arrives.

The fact that immune systems have evolved to cope with constant infections, and the traces of viral genetic material embedded in our own genomes from ancient viral infections, are testament to such evolutionary battles.

Beyond Omicron: what’s next for COVID’s viral evolution.

This is not the case: there is no predestined evolutionary outcome for a virus to become more benign, especially ones, such as SARS-CoV-2, in which most transmission happens before the virus causes severe disease.

Targets set for reduction should consider that circulating virus risks giving rise to new variants.

The more a virus replicates, the greater the chance that problematic variants will arise, most probably where spread is highest

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