The Covid testing dilemma

England’s pushing mass testing as a way to contain Covid. It’s free, it’s government approved, it’s somewhere between uncomfortable and painful, and it may or may not be a good idea. Let’s tear the numbers apart and see what we can figure out.

Since the schools reopened, secondary students–those are the older kids–have had to do quick Covid tests twice a week, and that’s been a bulwark of the program to keep the schools open while not letting the virus get out of control. 

The tests, unfortunately, have a reputation for being unreliable, especially when done by non-experts. Since the kids are doing their own tests, or asking their parents or three-year-old sisters to stick the swabs up their noses and down their throats, these are in the hands of the distilled essence of non-expert. One fear about relying on the quick tests has been that false positives will send a lot of people into isolation unnecessarily. So half of the positive tests were sent to a lab to be confirmed by the slower, more reliable tests, and only 18% of them were false positives. 

Irrelevant photo: Rhododendrons. Photo by Ida Swearingen

But wait, because we’re not done yet. Those numbers are from March, and Covid rates have fallen, at least in parts of the country. (Some hot spots remain, and I don’t know if numbers are falling there as well. Just put that possibility off to one side. The recipe may call for it later. If it doesn’t, we’ll stick it in the freezer.) The point is that where the number of cases is lower, everything changes

Why? Because the tests will crank out the same number of false positives, no matter how many people are infected. Find yourself a population of people who’ve never been exposed to Covid and the test will swear on any religious book you like that some of them are infected. 

I’m about to throw some numbers at you, so if your allergies are bad today just skip a few paragraphs.

Ready? In London, the southwest, the northeast, and the southeast of England, the prevalence of Covid ranged from 0. 08 to 0.02. In England as a whole, it was 0.12%. Using those figures (I’d assume that means the England-wide ones), it would take 16,000 tests to find one infected person. If the tests cost £10 each, that means spending £160,000 to find that one person.

Is that worth it? If we were trying to stamp the disease out and keep it stamped, as New Zealand is, it would be. Given that we treat stamping it out as the silly thought of irresponsible day dreamers, probably not. 

Meanwhile, in leaked emails (I do l love a good leak) “senior government officials” are talking about scaling back mass testing, although the Department of Health and Social Care says it has no plans to end the program. One in three infected people, they remind us, show no symptoms but is still contagious. 

That brings us neatly to the question of whether the rapid tests will spot that one person. In other words, it’s time to talk about false negatives. Administered by an expert, the tests pick up 79% of infections. Or to put that the other way around, they miss 21%, and those are mostly people with a low viral load. Or to put that another way, they’re most likely to miss people who don’t have symptoms, who are just the people the testing program is looking for.

Administered by secondary school students or their three-year-old sisters, they’re more likely to pick up 58% of infections, or to miss–umm– I think that’s 42%. Although estimates of the number of cases the test misses vary. It might be as high as 50%. 

The government denies that it has any plans to scale back anything ever and Boris Johnson is urging everyone to get tested twice a week. Even though his advisors say that in areas with low infection rates, only 2% to 10% of the positive results may be accurate. 

But what the hell, guys, we’ve got these tests. Someone’s cousin has the contract for them. Use them, will you, please? For the good of the nation.

 

News of an accurate rapid test that’s in development

A new test is being developed that’s both fast and accurate. It also tracks variants and tests for other viruses that might be mistaken for Covid. It can screen 96 samples at a time and within 15 minutes it starts to report the samples as negative or positive. In 3 hours, it will have sequenced all its samples. 

It’s also small and portable. It doesn’t make coffee, but it just might be able to make you a cup of tea.

Juan Carlos Izpisua Belmonte, a professor in Salk’s Gene Expression Laboratory where it’s being developed, said, “We can accomplish with one portable test the same thing that others are using two or three different tests, with different machines, to do.”

That’s the good news. But will it go from development to being manufactured and used?

Market analysis would be required to determine whether the initial cost of commercialization—and the constant tweaks to the test needed to make sure it detected new variants or new viruses of interest—are worth it.”

I believe that translates to “maybe.”

It’s called NIRVANA, which doesn’t seem to stand for anything, so I don’t know why it’s in all caps. 

 

High- and low-tech approaches to Covid

In New Zealand, they’re trying out an app that connects to smart watches and fitness trackers, monitoring people’s heart rate and temperature. It’s called an Elarm and the developer claims it can spot 90% of Covid cases up to three days before symptoms appear.

Does that include people who don’t go on to develop symptoms? I’m have to give you a definite maybe on that, because the article I found doesn’t address it. The company’s own website doesn’t answer the question either but says it will also let you know about stress and anxiety, although you might notice those without needing an app. Basically, it figures out your normal levels and lets you know when you’ve wandered off them, so you could end up going into isolation over the flu as easily as over Covid. That would scare the pants off you but would, at least, take a lot of the punch out of flu season.

So how do you use this? New Zealand wants its border force to try it out, since almost the only cases of Covid there are in incoming travelers, who have to go into quarantine, meaning the people who work for the border force are in the front lines.

When New Zealand says quarantine, by the way, they actually mean quarantine. It’s one reason they’ve been able to contain the virus.

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On the other end of the scale comes the recommendation that we open windows in public places to minimize Covid transmission. It’s cheap, it’s simple, and–

Oh, hell, how many public places these days have windows that open? Okay, ventilation. The air in public indoor spaces needs to be replaced or cleaned. 

We’ve heard a lot about keeping two meters (or yards) away from people to avoid contagion, but in addition to the heavier droplets people breathe out, which can carry Covid, the tiniest particles that we breathe out can also carry it, and they can stay suspended in the air for hours. The goal is to run them outside and get some fresh air in. 

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If you’re looking for a low-tech way to decide how far from people you should be standing, you can think of it this way: If you can smell that they’ve had garlic or peanut butter for lunch, you’re too close. 

 

Drug news

An asthma drug, budesonide, has been shown to shorten people’s Covid recovery time –and it can be used at home without anyone involved needing welding gloves, a deep-sea diver’s helmet, or a set of allen wrenches. It’s relatively inexpensive and comes in an inhaler. It shortened people’s recovery time by three days and at the end of two weeks the people who used it were in better shape than the control group.

It’s not clear yet whether it made hospitalization less likely. In the budesonide group, 8.5% were hospitalized. In the control group, that was 10.3%. That sounds like a result, but the problem with interpreting the numbers is that hospitalization rates are dropping in Britain. If you want to understand why that makes the numbers hard to interpret, you need to talk to someone who actually knows something.

Everyone in the test was over 50 and had underlying health problems. The drug can be used in the early stages of infection. 

The herd immunity debates

Professors at University College London grabbed some headlines with the news that Britain’s almost achieved herd immunity.

Should we celebrate? 

Nope. The small print said we can’t ease restrictions yet. “If we let up, that threshold will go up again and we will find ourselves below the threshold and it will explode again,” Karl Friston said.

This makes it sound like we’ve probably misunderstood what herd immunity means. Or else that the people who wrote the study have. I thought it marked the point where we could all wander back to whatever we can reconstruct of our normal lives, trusting that the virus will stay in retreat. Apparently not, though–at least not by this definition. 

Irrelevant photo: a rose. Indoors. It’s too early in the year for them outdoors yet.

In a rare moment when the health secretary, Matt Hancock, and I agree (I’m sure that upsets him as much as it does me; sorry Matt; it won’t happen often), he’s dismissed the suggestion of herd immunity, although his comments are oblique enough to be unquotable. They’re not incoherent but they’re not exactly to the point either. Never mind, though. I have agreed with him. It’s a rare moment. We need to mark the occasion.

Cup of tea, anyone?

Another estimate of herd immunity, this one from Airfinity (it “provides real time life science intelligence as a subscription service” and as part of that tracks vaccination programs around the world), sets it at the point where 75% of the population is vaccinated. The U.K.’s expected to reach that point in August, shortly after the U.S. and a few weeks before Europe.

Sorry about the rest of the world. It seems to have dropped off the map the article I found was using. 

There will, of course, still be a need to booster vaccines to keep up with the variants, at least until those countries that fell off the map get access to vaccines so are species can stop producing variants so prolifically. 

 

Creeping out of lockdown

As Covid deaths go down, Britain’s taken another step toward ending its lockdown, opening gyms, shops, pubs and cafes with outdoor seating, assorted other businesses. Internal tourism is causing traffic jams in all the usual places. 

About half the population has at least one dose of a vaccine. Will that be enough to keep the virus from rebounding? I wish I knew. Chile has an impressive vaccination program and unlocked too early, giving the virus the gift of a trampoline. Cases there have spiked. 

Optimist that I am, my mind snags on Britain’s remaining virus hotspots and on the two London boroughs where the government’s chasing cases of the South African variant. I expect they’ll do better with the variant than with the hotspots, because one of the things the government resolutely refuses to do is pay people a workable amount of money to self-isolate, and if you’re broke you’ll go to work, regardless of what the test says. Because you have to. 

On the other hand–and before I go on I should issue an Unimportant Personal Story Warning–I’m grateful to have stores open. I have a battery-operated watch whose battery stopped operating a while ago. (Whose idea was it to run watches on batteries, anyway? I seem to remember winding my watch every day without feeling unduly burdened. I didn’t even break a sweat.) 

How long ago did the battery run out? No idea. We were in lockdown. Who needs a watch? But eventually I did need a watch and I noticed that mine was no longer in touch with consensual reality. So I got a battery (thanks, Tony). I opened up the back (thanks, Ellen), took out the old battery, put in the new one, put the innards back together, and was just starting to congratulate myself when I found that I couldn’t fit the back on, making the whole project pointless. I put a rubber band around the thing and left it alone.

I still didn’t have a watch.

On Monday, the first day that unimportant stores were open, I took it to a jeweler. Jewelers have a little gizmo to hold the back in place while they thump it shut. I now have a working watch.

I don’t need it more than once a week. We’re still halfway locked down. 

So yes, it’s nice to be able to do that sort of small thing. It also makes me nervous–and it should.

 

Lockdown and the economy

Britain’s economy’s now in the worst recession it’s had in 300 years. Worse than the Great Depression of the 1930s? Apparently. To find one that was worse, you have to go back to the great frost of 1709, when Britain was an agricultural country.

On the other hand, having shrunk 9.9%, the economy then grew by 1% in the last quarter of (I believe) 2020. Household savings during the pandemic reached £140 billion–16.3% of people’s disposable income. That’s compared to 6.8% in 2019. Predictably, that’s unevenly distributed, with some people building up savings while others struggle to hold onto their homes and food banks struggle to keep up with need. 

It’s a lovely way to organize a world. 

 

The Covid risk indoors and out

Want to figure out the Covid risk people face indoors? Measure the carbon dioxide level

This works because–well, the thing about infectious people is that they exhale. Admittedly, uninfected people do too. You probably do it yourself. And all that exhaled carbon dioxide joins together and either stays in the room or doesn’t. The Covid virus does exactly the same thing: It either stays in the room or if the room has enough ventilation it wanders out into the world, where it poses next to no danger.

The thing is that carbon dioxide levels can be monitored cheaply. If you see them rise, you still won’t know if anyone infectious is breathing into the mix, but you will know that the ventilation isn’t what it needs to be and it’s a risky place to stand around inhaling. At that point you can (a) limit yourself to exhaling, (b) leave, or (c) improve the ventilation. Preferably (b), since that will help everyone.

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An Irish study reports that roughly one Covid case out of a thousand is caught out of doors. 

Professor Orla Hegarty said, “During Spanish flu people were advised to talk side by side, rather than face to face, and this is borne out by how viral particles have been measured moving in the air when people breath and speak.

“The risk of infection is low outdoors because unless you are up close to someone infected, most of the virus will likely be blown away and diluted in the breeze, like cigarette smoke.”