Think lockdown’s ov er the top? Read this chilling account and you may think again

A single cough, a hand on a door – and, in disquieting detail, the truth about how the virus can take hold of anyone, with devastating effects

YEOU call a friend and arrange to meet for lunch. It is unseasonably warm, so you choose a restaurant with outdoor seating, which you reason should be safer during the coronavirus crisis.

As usual, you take all sensible precautions. You use hand sanitiser, sit a good distance from other customers and try to avoid touching your face, though that last bit is hard to remember.

A part of you suspects that the whole thing might be overblown. What you don’t know is that ten days ago, your friend’s father met a business acquaintance from whom he caught coronavirus.

Three days after that, your friend’s father coughed into his hand before opening the door of his house to welcome home his son. The saliva of Covid-19 patients can harbour half a trillion virus particles per teaspoon, and a cough ‘aerosolises’ this into a diffuse mist.

As your friend walked through the door, he took a breath and 32,456 virus particles settled on to the lining of his mouth and throat.

Viruses have been multiplying inside his body ever since.

And as he talks, the passage of his breath over the moist lining of his upper throat creates tiny droplets of virus-laden mucus that waft invisibly into the air over your table. Some settle on the as-yet-uneaten food on your plate, some drift on to your fingers, others are drawn into your nasal sinus or settle in your throat.

By the time you extend your hand to shake goodbye, your body is carrying 43,654 virus particles. After you’ve shaken hands, that number is up to 312,405.

One of the droplets gets drawn into the branching passages of your lungs and settles on the warm, wet surface, depositing virus particles into the mucus that coats the tissue there. ACH particle is round and very small: if you magnified a human hair so that it was as wide as a football pitch, the virus particle would be just four inches across on the same scale.

The virus’s outer membrane carries jagged molecules called spike proteins. These stick out like the protrusions on a dog’s knobbly-ball chew-toy.

In the middle of the virus is a coiled strand of RNA, the virus’s genetic material.

As the virus drifts through the lung’s mucus, it bumps into one of the cells that line the surface.

This lung cell is considerably larger than the virus; on the football-pitch scale, it’s eight metres across. A billion years of evolution have equipped it to resist attackers. But it also has a vulnerability – a backdoor.

Protruding from its surface is a chunk of protein called an ACE2 receptor.

Normally, this helps to manage hormone activity in the body. Today, it’s going to serve as an anchor for the coronavirus.

As the spike protein hits the surface of the lung cell, its shape matches that of the ACE2 so closely that it sticks to it like glue.

The membrane of the virus then fuses with the membrane of the cell, spilling the RNA contents into the lung cell. The virus is in.

The virus’s RNA gets busy, hijacking the cell’s own machinery to force it to make more copies of the virus.

Other viral proteins block the cell from fighting back. Soon the cell’s normal business is completely overwhelmed by the demands of the viral RNA, as it builds countless replica viruses.

These travel towards the surface of the cell, which then bursts open and releases new virus particles into your body by the hundreds of thousands.

All up and down your lungs, throat and mouth, the scene is repeated over and over as cell after cell is penetrated and hijacked.

The replicated viruses spill out, invade the bloodstream and pour through the digestive system. You don’t feel any of this. In fact, you still feel completely fine. If you have any complaint at all, it’s boredom.

You’ve been a dutiful citizen, staying at home to practise social distancing. But after two days of watching Netflix, you decide that your mental health is at risk if you don’t get outside.

You call a friend and she agrees to meet you for a walk along the river.

You’re hoping to enjoy your time together, but the facemask your friend is wearing spoils the mood. She gives you a warm hug as you say goodbye, and though you tell her it was great to see her, you leave feeling deflated.

What she doesn’t know is that an hour before, you went to the lavatory and neglected to wash your hands afterwards.

THE invisible smear you leave on the arm of her jacket contains 893,405 virus particles. Fortyseven seconds after she gets home, she’ll hang up her coat and then scratch an itch at the base of her nose just before she washes her hands. In that moment, 9,404 viral particles will transfer to her face.

In five days, an ambulance will take her to hospital.

Meanwhile, your own infected cells spew out virus particles until they burn themselves out and expire.

As fragments of disintegrated cells spread through your bloodstream, your immune system finally senses that something is wrong.

White blood cells detect the fragments of dead cells and release chemicals called cytokines that serve as an alarm signal, activating other parts of the immune system to swing into action. When immune cells identify an infected cell, they attack and destroy it.

Within your body, a microscopic battle is raging, with your immune system levelling its heavy artillery on both the enemy’s trenches and its own troops.

As the carnage mounts, the body’s temperature rises and the infected area becomes inflamed.

Two days later, sitting down to lunch, you realise that the thought of eating makes you feel nauseous. You lie down and sleep for a few hours. When you wake up, you realise that you feel even worse. Your chest is tight and you have a persistent dry cough. You wonder: is this what Covid-19 feels like?

You rummage through your medicine cabinet and find a thermometer. You hold it under your tongue for a minute and then read the result: 38.9C.

You crawl back into bed. You tell yourself that it might just be

flu, and even if the worst comes to the worst, you’re young(ish) and otherwise healthy. You’re not in the high-risk group.

You’re right, of course, in a sense. For most people infected with the coronavirus, that’s as far as it goes. With bed rest, they get better.

But for reasons scientists don’t understand, about 20% of people get severely ill. Despite your relative youth, you’re one of them. After four days of raging fever and feeling sore all over, you realise that you’re more ill than you’ve ever been in your life.

You’ve got a dry cough that shakes you so hard, your back hurts. Fighting for breath, you order a taxi and head to the nearest accident and emergency unit. (You leave 376,345,090 virus particles smeared on various surfaces of the cab and another 323,443,865 floating in the air.)

AT THE hospital, you’re examined and sent to an isolation ward. As doctors wait for the results of a test for the coronavirus, they administer a CT scan of your lungs, which reveals tell-tale fuzzy spots caused by fluid accumulating where the immune-system battle is the most intense

Not only do you have Covid-19, but it’s led to an intense and dangerous pneumonia called acute respiratory distress syndrome, or ARDS. With all the regular beds occupied by the many Covid-19 sufferers, you’re given a space in a room alongside five other patients.

Doctors put you on an intravenous drip to supply your body with nutrients and fluids as well as antiviral medicine.

Within a day of your arrival, your condition deteriorates. You vomit for several days and start to hallucinate. Your heart rate slows to 50 beats per minute.

When a patient in the next room dies, doctors take the ventilator he was using and put you on it.

By the time the nurse threads the endotracheal tube down your throat, you’re only half-conscious of the sensation of it snaking deeper and deeper toward your lungs.

You lie there as she places tape over your mouth to keep the tube in place.

You’re crashing. Your immune system has flung itself into a ‘cytokine storm’ – an overdrive of such intensity that it is no longer fighting just the viral infection but the body’s own cells as well.

White blood cells storm your lungs, destroying tissue. Fluid fills the tiny sacs in the lungs that normally let the blood absorb oxygen. Effectively, you’re drowning, even with the ventilator pumping oxygen-enriched air into your lungs.

That’s not the worst of it. The intensity of the immune response is such that under its onslaught, organs throughout your body are shutting down, a process known as multiple organ dysfunction syndrome, or MODS.

When your liver fails, it is unable to process toxins out of your blood, so your doctors rush to hook you to a round-the-clock dialysis machine. Starved of oxygen, your brain cells begin to expire.

You’re fluttering between life and death. Now that you’ve slipped into MODS, your odds are 50-50 or worse.

OWING to the fact that the pandemic has stretched the hospital’s resources past breaking point, your outlook is even bleaker.

Lying in your bed, you half-hear as the doctors hook you to an extracorporeal membrane oxygenation (ECMO) machine.

This will take over the work of your heart and lungs and hopefully keep you alive until your body can find its way back to equilibrium.

And then you are flooded with an overwhelming sense of calm. You sense that you have reached the nadir of your struggle. The worst of the danger is over.

With the viral attack beaten, your body’s immune system will pull back, and you’ll begin the slow, painstaking journey to full recovery.

Some weeks from now, the doctors will remove the tube from your throat and wheel away the ventilator. Your appetite will come back, the colour will return to your cheeks, and on a summer morning you’ll step out into the fresh air and hail a taxi for home.

That’s what your mind is telling itself, anyway, as the last cells of your cerebral cortex burst in starburst waves, like the glowing algae in a midnight lagoon.

In the isolation ward, your ECG goes to a steady tone. The doctors take away the ventilator and give it to a patient who arrived this morning.

In the official records of the Covid-19 pandemic, you’ll be recorded as victim number 592.