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. 

How to eliminate Covid, and other pandemic news

 

Academics at the University of Otago studied New Zealand’s experience with Covid and say that the virus can be eliminated, not just contained. 

The emergence of an apparently more infectious virus variant is just another reason to eliminate this infection,” they said

Actually only one of them said it, but let’s pretend, for the sake of simplicity, that they spoke in unison. They do stuff like that in New Zealand. 

What you need if you’re going to eliminate the virus, they said, is informed input from scientists, political commitment, sufficient public health infrastructure, public engagement and trust, and a safety net to support vulnerable populations. 

Those will be easier to cobble together in some countries than in others. That’s me speaking in unison and not mentioning any countries by name. To protect the guilty. 

Irrelevant photo: Crocuses. They’ll be coming up soon, and they’re not afraid of the corona virus.

One of the barriers to eliminating the virus is the belief that hard measures will hurt the economy more than half measures, causing greater hardship, which (as advocates of half-measures reminded us at the start of this mess) has its own health impacts.

“Our preliminary analysis suggests that the opposite is true,” the academics said. “Countries following an elimination strategy—notably China, Taiwan, Australia and New Zealand—have suffered less economically than countries with suppression goals.”

The introduction of vaccines should make elimination easier.

 

Antibody therapy

Scientists are testing an antibody therapy that could prevent someone who’s been exposed to Covid from going on to develop it. It could, at least initially, contain outbreaks–in nursing homes, hospitals, or universities, say–or protect people in households where one person is known to be infected. They’re also investigating the possibility that it could protect people with compromised immune systems. 

If all goes well–please notice the if in that sentence–it could be available in March or April.

The Pfizer and Oxford vaccines don’t confer immunity for about a month after injection. With this, the immunity would be immediate.

It goes by the snappy name of AZD7442. 

 

Mass testing evaluated

Britain tried a mass testing program in Liverpool, using rapid-result Covid tests, and managed to miss over half the cases. 

So was it worth doing?

A study went through the data and came back with a definitive maybe. In this corner, wearing the electric pink tee shirt that says No, is the danger presented by false negatives. People who test negative but in reality carry the virus may be prone to riskier behavior than people who haven’t been given any reassurance. They think they present no threat, so they may spread the disease more.

And in this other corner, wearing the soothing green tee shirt that says Yes, is the benefit that comes with spotting Covid cases that would have been missed and taking those people out of circulation. Assuming, of course, that they actually do take themselves out of circulation, which most of them will. 

I think.

The Liverpool data hint that the test may spot people with the highest viral load–in other words, people who may be the most infectious–while missing those least likely to be infectious. But you might want to notice how many tentative words wiggled their way into that sentence. It hasn’t been established that a light viral load means you’re less infectious. 

People who are asymptomatic, by the way, can still have a high viral load, and an estimated 40% to 45% of cases are asymptomatic.

So is mass testing with rapid tests worth doing? It’s a matter of weighing the possible gain (spotting cases that would otherwise have been invisible) against the possible harm (giving false reassurance to people who are in fact carriers). And it depends on that unknown: how contagious people with low viral loads turn out to be.

Whatever it is you come here for–and that’s still a mystery to me–it’s not rock-solid certainty, is it?

 

The compassion report

With a show of compassion worthy of the current American and British governments, Colombia’s president announced that the country will refuse Covid vaccines to hundreds of thousands of Venezuelan refugees. The only refugees who’ll have access to the vaccine are those with dual citizenship or official status. That’s less than half of them, and more are crossing the border daily.

The idea that no one will be safe until we all are is a hard one to get across. As will that business the academics from Otago mentioned–political commitment. 

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A bookstore in Trieste asked for volunteers to call people trapped at home by the virus and spend twenty minutes at a time reading to them over the phone and just generally chatting. They figured they’d be doing well if they found a few people to help out the three staff members who were already doing making calls during their breaks and on their days off.

They got 150 responses. Some were from Italians living abroad. Some came from a theater company that had itself been trapped by the pandemic–not at home but offstage. Some were I have no idea who–people who don’t fall into such neat categories. The plan was to have the calling run during Christmas, but with the response it’s gotten it now has no end date.

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An Amsterdam museum that sold a Banksy work for £1.5 million so that it wouldn’t have to lay off staff had a bit of compassion and goodwill returned to it. The anonymous buyer emailed a few months later and offered to lend it to the museum for at least a year.