I’d like to talk about the other pandemic: the one caused by marauding chocolate bars rather than somebody sneezing. It’s been rather upstaged for obvious reasons, but it’s doing amazingly well. According to WHO, obesity affects well over 2 billion people and kills roughly 2.8 million a year. That’s enough to fill nearly 30 countries the size of Britain entirely with overweight and obese people, and wipe out the population of Wales every year. Although not necessarily in Wales; obesity gets everywhere, even places where not long ago, people were hard put to get enough to eat.

And although not the most burning issue of the day, it’s still a hot topic because Covid is particularly good at killing people who are fat, and in Britain 64 per cent of people are overweight or obese.

So how has it achieved this runaway success?

Well, to start with, the vectors are magnificently effective. For the first time in the history of pandemics, they are almost entirely manmade – created in laboratories and mass-produced in factories. It’s a work of genius: pouring sugar into cans of fizzy water; turning corn into syrup and injecting it into practically everything; blanketing innocent little biscuits in thick layers of chocolate – they’ve come up with infinite ways to get our fat-cells beautifully plumped up. Right down to the hi-vis, shiny plastic wrappers and employing master-flavourists to make them irresistible, the creators have thought of everything; they’ve even managed to get them classified as food.

And it’s not just the vector design that is so impressive: the vector delivery model deserves a Nobel Prize for services to death: instead of relying on the vagaries of mosquitos or fleas – or worrying that people might use masks to prevent air-borne infection – the vectors are placed in every possible location: schools, shops, service stations, restaurants, cafes, bars, hospitals and sports facilities. It’s easier to social-distance from a grandchild than a bar of chocolate. And any time we are not in the physical vicinity of weight-boosting substances, the best Oxbridge and Ivy League brains are paid handsomely* to come up with messages to remind us, on television… billboards… social media… magazines… newspapers, how much better our lives would be if only we ate more of them.

*I would like to take this moment to reassure shareholders and pension fund managers that food conglomerates do not waste their millions on marketing strategies that do not work.

It has to be said that the obesity vectors couldn’t work without enthusiastic cooperation from our genes – the ones that are determined that we should get fat and stay fat in order to get through the next famine. But I think they can still take the credit; the genes have been there all along, though they were getting nowhere on their own.

And some people are apparently immune: they consume the vectors by the bucket load and stay exactly the same weight. If they’d been cave-dwellers, they’d be dead, but in the 21st century they can smugly pat their flat stomachs while they sink their teeth into their second Big Mac. But for those of us with survival-of-the-fattest genes, the vectors super-size our evolutionary advantage.

The manufacturers – often backed up by government – make it quite clear that consuming their obesity-in-a-bag is entirely a personal choice. And let’s be even clearer: if you get fat, it’s your own fault. But in the dense junk-food jungles with all the product-placement and nudge techniques, personal choice gets rather lost.

For example, for much of the year, my local Co-op displays chocolate, sweets, and crisps in 16 different locations: whether you are looking for apples or loo paper, they will probably be sitting next to a pile of chocolate bars.

Queuing to pay for petrol, you shuffle past a 30ft-long wall of chocolate; in the unlikely event you have resisted picking up your Mars-a-day by the time it’s your turn to pay, there are probably bags of doughnuts grinning enticingly beside the till.

In W.H. Smiths – and increasingly, other places  – when you get to the till, they point to a chocolate bar the size of a small lawn and ask if you’d like to buy it for a pound.

At many fast-food and restaurant chains, sugar-in-a-can drinks and pudding and are included in meal-deals, but you have to pay extra for vegetables.

Every Thursday, I get a text from Vodafone with an offer of free popcorn or sweets, and in the mile or so that I walk to get fresh fruit and veg at my local market, I pass 22 opportunities – each way – to buy fast food or ready-wrapped, weight-boosting substances.

There is no limit to where and when you can get hold of them, and no law against underage junk-fooding:  if a four year old tips up at the checkout with a shopping trolley filled with Maltesers, Mini Eggs, and Cadbury Dairy Milk, so long as they have the money to pay for it, there’s nothing to stop them.  My four year old is hypothetical, but there was nothing hypothetical about the queues of schoolchildren stocking up with sweets at the Co-op on the way to school.

And on top of the almost infinite opportunities to boost your weight, it’s remarkably difficult to find food on the go that’s not calorie-dense – and if you do, it is often quite expensive and not substantial enough to fill you up. Unless you are a self-control superhero, the chances are that halfway through the afternoon you will succumb to a KitKat, especially if it has been winking at you all day from a vending machine.

We don’t all succumb to the marketing wiles, but if we manage to get safely home and slam our front doors against the onslaught of chocolate, chips and pizza, we are unlikely to be dreaming about boiled carrots for dinner.

But although the drive towards global obesity has been a total masterpiece, its progenitors are reluctant to take the credit. They’re not unique in this. If asked about malaria, the average mosquito would look at you blankly and say “look mate, I just needed to suck a bit of blood.” The obesity manufacturers say the same.

To be fair, their aim is wealth not fat creation – and the economic imperatives are serious: in Britain alone, the food industry contributes billions to the economy and provides hundreds of thousands of jobs. Many shops rely on selling high volumes of obesity-in-a-bag to remain viable, especially given the structure of business rates and sky-high rents. The hospitality sector needs us to eat up our pudding and drink buckets of wine or people’s livelihoods disappear – and the government would be hard put to cope without all the tax revenue. Economically speaking, it is our patriotic duty to eat ourselves fat.

However, the world didn’t respond to malaria by letting mosquitos swarm wherever they felt like it, and they didn’t blame people for getting ill from the bites. And we have seen from Covid what governments are prepared to do to prevent a massive death toll. So perhaps it’s time to liberally douse the food conglomerates with DDT, and start to limit where, when, and how they can peddle their wares. This is not about limiting our freedom and personal choice; it’s about limiting the freedom of the obesity merchants to do everything in their power to persuade us to make the wrong choice.

It would be difficult economically, and would require significant changes to make the retail sector viable without needing to peddle obesity to survive. But imagine how many people might have survived the Covid pandemic if they had not been fattened up for profit.

Lizzie Wingfield is a classical singer, a performance psychologist and a cook who writes about her experience of staying in the thin lane.