Issue 99

Pus, Covid contacts, and international vaccine generosity

October 11, 2020

Hello friend! Welcome to Scrap Facts.

I'm a reporter covering health and science with insatiable curiosity. I love everything I learn, not all of which gets its own story. Each week, I'll bring you some of my favorite facts that I picked up on the job or while out living life.

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Pus is an example of the extremes your immune system will take to protect you.

Found while reporting: What we (don’t) know about Trump’s Covid-19 long-term prognosis.

To understand how your body’s immune system changes with age, we need to talk about pus.

Pus—specifically, that yellowish oozy stuff that comes out of cuts or other wounds—is not inherently bad. It means that you’ve been exposed to some potential infectious agents, but it also means that your immune system is on it.

Your body’s immune system is comprised of hundreds of kinds of cells, which can broadly be categorized as innate or adaptive. Innate immune cells are fast-acting and less specialized; they respond the same way to all pathogens, sometimes doing extra damage along the way. Adaptive immune cells are slower, but then they fight specific pathogens like little cellular assassins.

Neutrophils are a kind of innate immune cell that patrol your bloodstream. As soon as they chemically detect a pathogen from the outside world—like somewhere you scraped yourself after a fall—they rush to the scene and kamikaze themselves, Matthew Woodruff, an immunology researcher at Emory University in Georgia, told me. Pus’ sticky, slimy qualities comes from neutrophils’ DNA as they bust up their nuclei. This act of self-destruction makes the immediate environment difficult for bacteria or viruses to live in, and sends chemical signals calling for backup. Some of your own tissue gets damaged in the process, too, but the idea is that you can repair yourself after the infection is stomped out. Neat, right?

We need both our innate and adaptive immune systems, but they’ve got to be balanced. If we only had the adaptive immune system, we’d be too slow to respond to infections. If we only had our innate immune system, their aggressive response would ultimately damage our own bodies too much. We’ve seen this with Covid; in a lot of severe cases, the infection overwhelms our innate immune system in a way that’s potentially lethal.

As we age, though, our immune system gets out of whack; it tends to produce way more innate immune cells than adaptive cells. This is one of the reasons why older adults have such a hard time fighting off Covid; they’ve got too much of these aggressive, destructive cells and not enough of the specialized fighters. And in turn, it takes longer for them to produce antibodies, and they may not make as many of them.

There are other reasons it’s harder for older adults to fight off Covid; as we age, our lungs get stiffer. The muscles that help us breathe get weaker, and our hearts get larger with slower electrical signaling, Candace Brown, a professor of gerontology at the University of North Carolina, Charlotte, told me. The degree to which this happens depends on factors—like diet and activity levels—of course, but it’s there for everyone. And that’s before we even consider preexisting conditions like heart disease or diabetes.

How much of this will affect the US president? Who knows—I don’t think it’s wise to speculate on specifics. But I do know that it’s also foolish to think that he’s in tip top shape less than two weeks after his hospitalization.

Contract tracing was never designed to work backwards—which means that even when it works perfectly it’ll probably miss people.

Found while reporting: The challenge of contact tracing Covid-19 in the White House.

When we think about contact tracing, we’re really thinking about a specific set of rules that the US Centers for Disease Control and Prevention has come up with. The process is all about finding all the people a person with a symptomatic Covid-19 infection has come into contact with in the 48 hours before they started showing symptoms, which is generally four days after they got infected.

First, we have to think about the timing of the infection. On average, the first two days after someone is exposed to the virus, they aren’t infectious. The virus is still incubating, which means it’s replicating to reach a critical mass in the body. Two days after that, the virus has had enough time to sufficiently copy itself to make a person infectious to others, even if they still feel fine. This window is the danger zone.

By the time a person actually feels sick, it’s usually been another 48 hours, so four days after they were exposed. Theoretically, a person who knows they’re sick will properly isolate themselves while they recover.

Then there’s the issue of identifying contacts. From an infectious disease perspective, “contacts” are people who have physically touched the now-sick individual, or people who have been within 6-ft of someone indoors for more than 15 minutes. (The exception is if one person wearing a clean, properly-fitted N95 mask; they wouldn’t be considered a contact because the medical-grade masks should protect them.) These contacts would need to quarantine for 14 days to make sure they don’t infect anyone else, even if they don’t develop symptoms. If they do, they should wait about 14 days after their symptoms started—maybe longer if they’ve got a more severe case.

Technically, an infectious person could go to a grocery store and not talk to anyone for a long period of time, and there would be 0 contacts. However, this person could still potentially infect others, though, which is why it’s a good idea for everyone to wear masks (even if they aren’t N95s) and practice good hand hygiene. These people wouldn’t be contacted by a public health department’s contact tracers, however.

What’s confusing about all this, though, is that these rules were created on the average incubation time of the virus and the average transmission rate. Infectious disease biology is more like the English language; it doesn’t strictly follow the rules, and sometimes evades them altogether. Some people are super-spreaders who never feel sick, but are still infectious; others get sick, but avoid giving Covid-19 to anyone else.

Which basically means it’s impossible to go back in time to figure out who the origin of an outbreak was. You’d want to go backward in time so you could conceivably go forward and contact everyone who should quarantine themselves. To do that, you’d have to know exactly how long these incubation/symptomatic periods were in individual cases. But we don’t have the means of doing that—which is why outbreaks, like the one at the US White House recently, often go unchecked and out of control.

A map of all the countries that are committed to making sure a Covid-19 vaccine is globally available, and those that aren’t.

Found while reporting: The nations opting out of a plan to ensure global access to Covid-19 vaccines.

Last month, a report on Covid-19 and global health stated that the fastest way to end the global pandemic was to ensure that every country had adequate access to vaccines when they’re available.

Gavi, the vaccine alliance, and the World Health Organization have created an advanced marketing campaign in which rich countries can chip in to buy vaccines for countries that may not be able to afford them. In the map below, the blue countries are those that have committed to this fund, the pink countries are those that could benefit from it, and the grey are those that have remained silent on the matter.

Most of the map is colorful. The grey spots on the map are Kazakstan, Mauritania, the Western Sahara, Guinea, Togo, Ghana, Malaysia…and the US, China, and Russia. Three of these countries are not like the others. The latter are allegedly global superpowers financially capable of buying vaccines for other countries, but they’ve mostly bought up pre-orders of vaccines for their own citizens.

Bonus fact: If you’re healthy want to actually try to speed up the end of the pandemic on an individual level, you could volunteer to participate in a late-stage vaccine clinical trial. There’s some financial compensation and medical care should you get sick or have any reaction to the vaccine. You can read about the process in this story I wrote a few weeks ago.

Other work you may have missed:

The two women who made history by jointly winning the Nobel Prize in chemistry are also badass entrepreneurs. Between them, they have six biotech startups utilizing different aspects of Crispr, the gene editing system they discovered. Three of these companies have gone to IPOs. These women were also the sixth and seventh to win Nobels in chemistry; there have been 185 male winners.

Your Instagram feed is lying to you: There are way more people who hate cooking than those who love it. I am happily in the cooking-hating crowd, but I’ve learned a few tricks to make it a little more bearable. I wrote about how figuring out why you don’t enjoy cooking can help you figure out how to learn to like it—or at least tolerate it.

Covid-19 could change sexual health monitoring for the better. There’s always been stigmas around STIs. But now, we’ve got the technology to collet the necessary samples for STI testing from home. What if, like Covid-19 testing, you could just take an at-home test instead, and get a call from a health care provider if you needed it? I’m betting that this option will stick around long after the pandemic.

The US government is funding gun injury prevention work for the first time in 24 years. The hiatus was caused by a 1996 amendment authored by Jay Dickey, a representative from Arkansas, who argued that federal money shouldn’t go to gun control research. He later regretted that it stopped all gun research entirely. President Trump signed this new funding into law years ago in Dec. 2019, and projects are just getting started now.

Wastewater-based epidemiology: so hot right now. So many people want to track poop for bits of Covid that the equipment needed to do it is running low.

And finally, here’s a review of Kissing the Coronavirus, a $0.99 Kindle book I’m sorry to have stumbled on that made the Politico Nightly newsletter this Friday. You can read the entire issue of the newsletter here (the review is at the bottom), or just read the excerpt below:

That’s all for now—stay curious, friend ❤️

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Top image by E. Y. Smith, headshot drawing by Richard Howard.