The term 鈥�endemic鈥� is increasingly being used by politicians in relation to covid-19. But the term has no single agreed definition and doesn鈥檛 mean that it is safe to stop restrictions, such as wearing masks and limiting social gatherings.
On Tuesday, Marco Cavaleri at the European Medicines Agency that 鈥渨hat we鈥檙e seeing is that we are moving towards the virus being more endemic鈥�. The previous day, European officials should reclassify covid-19 as an endemic illness due to falling death rates. Last week, the UK鈥檚 education minister, Nadhim Zahawi, said the country is 鈥渨itnessing the transition of the virus from pandemic to endemic鈥�.
But at a press conference on Tuesday, Catherine Smallwood at the World Health Organization Europe said . 鈥淓ndemicity assumes that there鈥檚 stable circulation of the virus, at predictable levels with predictable waves of transmission鈥� that doesn鈥檛 rely on external forces being placed in order to maintain that stability.鈥�
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Among infectious disease specialists, endemic may be used in contrast to the term epidemic. An epidemic of a disease means there is a surge in cases, perhaps because a pathogen has crossed over to a new species, as in the case of covid-19. A pandemic is an epidemic that has spread over several continents.
If a disease is endemic, on the other hand, the number of cases is broadly stable, although there can be seasonal fluctuations. Measles is said to be endemic in many countries. Malaria is endemic in some regions, although it may rise in the rainy season.
Endemic conditions can still cause serious illness and require stringent measures. Malaria kills hundreds of thousands of people every year.聽 Smallpox, too, was endemic before we eradicated it, and it killed nearly a third of those who caught it.
Given that many countries are in the middle of a massive surge of cases caused by the omicron variant, it seems hard to argue that covid-19 is currently endemic. 鈥淚 don鈥檛 think we鈥檙e actually anywhere near endemic,鈥� says at the University of Warwick, UK. 鈥淚 think a lot of it is wishful thinking.鈥�
What might endemic covid-19 look like? The coronaviruses that cause common colds, such as OC43, seem to reinfect people every three to six years. As with covid-19, immunity to reinfections doesn鈥檛 last long, but immunity to serious illness does.
If OC43 reinfections occur every four years, that would mean about 45,000 infections a day in the UK. 鈥淭hat is a reasonable estimate of how many covid-19 infections there will be each day, averaged over a few years, when we reach the endemic equilibrium,鈥� says at the University of East Anglia, UK. At the moment, the UK is recording about 200,000 covid-19 cases a day, and there will be many more going unconfirmed by testing.
The number of daily new omicron cases in the UK seems to have recently started falling, as they have done in South Africa, where the variant was first seen. But another covid-19 variant may well emerge this year or next to cause a further surge 鈥� although it is possible that the level of immunity in populations, caused by both vaccines and infections, will continue to offer increasing protection against severe illness.
So we may only be able to say when covid-19 has become endemic by looking backwards. 鈥淥ften you don鈥檛 know when that transition has occurred, except in retrospect,鈥� says Hunter.
