IRA FLATOW: This is Science Friday. I’m Ira Flatow. Later in the hour, sleeper cancer cells awakened by chemicals all around us and the story of why researchers glued tiny capes on termites. I don’t think you can do this one at home.

But first, syphilis is on the rise in the US. A new federal report on sexually transmitted infections in Americans revealed syphilis cases rose 80% between 2018 and 2022 with total cases being more than 200,000. That’s the highest count in the US since, what, 1950.

But while the syphilis epidemic is growing, other STI rates are down. Joining me to help explain this and other science news of the week is Rachel Feltman, host of the podcast The Weirdest thing I Learned this Week. Welcome back, Rachel.

RACHEL FELTMAN: Thanks for having me, Ira.

IRA FLATOW: All right. This case of sexually transmitted infections and syphilis, what’s going on here?

RACHEL FELTMAN: Yeah. So as you said, we’ve seen an 80% rise since 2018, and these are the 2022 numbers, which just got released. And the CDC was very clear that they suspect 2023 was worse.

Obviously, this is troubling, but it’s not surprising. For the past few years, every time these reports have come out, the CDC has been sounding the alarm on syphilis. They think this is due to a decrease in condom use but also largely due to issues in access to good health care, social and economic conditions, stigma. So a lot of this has more to do with deep systemic issues than with anything actually related to sexual behavior.

IRA FLATOW: What do you mean by deep systemic issues, something about differences in people or what?

RACHEL FELTMAN: Yeah. So we’re seeing people having a real lack of access to reliable, consistent, affordable health care. And with syphilis, we do see the worst surges are in the group known as men who have sex with men, which is largely probably tied to a decrease in condom use. But we also see rising rates in people of color, in women of color, especially. So that, public health researchers think, really comes down to not just social stigma but just a question of whether people have regular access to checkups and the kind of relationships with their doctors where they’re having conversations about screening for syphilis and other STIs.

IRA FLATOW: Well, there are– speaking of other STIs, how are they comparing to the syphilis cases?

RACHEL FELTMAN: Yeah. So the good news is that chlamydia has finally leveled out, and gonorrhea has actually gone down for the first time in a decade. And a few years ago, gonorrhea was really what the CDC was concerned about. They were very worried that we were going to see a surge in antibiotic resistant gonorrhea, that we were going to run out of antibiotics that work for it.

So it’s great news that those cases are going down. But those are– chlamydia and gonorrhea, those are very likely to cause immediate and noticeable symptoms that don’t go away until you go get treatment for them. Syphilis often is pretty easy to ignore. The initial symptoms tend to go away, and it causes issues later, particularly with congenital syphilis, which is when children are born infected with syphilis. And that has surged by more than 900%.

IRA FLATOW: Wow.

RACHEL FELTMAN: Yeah.

IRA FLATOW: Wow.

RACHEL FELTMAN: And that’s very concerning and also totally avoidable because all that has to happen is that people get screened and they get treated with antibiotics. So again, that’s a real indicator that this is an issue with disparities in health care as opposed to, a few years ago, every time the CDC report came out, people would be like, is Tinder the problem? So I’m glad we’re getting away from that talking point. But this is definitely a concerning thing.

IRA FLATOW: Well, speaking of concerning, scientists have documented the first-ever case of Alzheimer’s disease being transmitted. What’s happening here?

RACHEL FELTMAN: Yeah. So the important thing to note about this before we get into it is that there’s absolutely no way that people will catch Alzheimer’s disease from other people who have it. No one has to be concerned about providing care or sharing space with someone who has Alzheimer’s disease. But this is a very weird specific medical phenomenon that could actually help us learn more about how Alzheimer’s works.

Basically, it turns out that some people who were treated with human growth hormone taken from the brains of human cadavers, which is a procedure that was banned 40 years ago and, in retrospect, seems like, obviously, a bad idea, but we’ve learned a lot about neurological disease since 40 years ago.

It turns out some people who receive this treatment may have been sort of seeded with the beta amyloid proteins that lead to Alzheimer’s, and that led to them developing very unusual cases of Alzheimer’s, some as young as in their 30s. But the fact that this happened through to the transmission of brain material from another human could actually help us better understand the mechanisms that cause Alzheimer’s in all patients.

IRA FLATOW: That’s cool. We’ll learn something from this.

RACHEL FELTMAN: Yes, hopefully.

IRA FLATOW: Yeah. Let’s go on to your next story, and for this one, we need to head into the Wayback Machine to go back in time to when Homo sapiens and Neanderthals lived side by side. Now, we knew that happens, but there’s more information about just how long this period lasted.

RACHEL FELTMAN: Yeah. New evidence from this cave in what’s now Central Germany shows that humans, Homo sapiens, rather, were in Northern Europe 45,000 years ago, which is several thousand years earlier than we had evidence of our ancestors being there before. And we know that Neanderthals were there during that time.

So this basically pushes back the date of when we know that Homo sapiens and Neanderthals were hanging out in the same space by a few thousand years. And it’s just continuing to chip away at this, at this point, pretty defunct idea that humans hit the scene and Neanderthals were toast immediately.

We know, of course, that, actually, there was a lot of interbreeding, that Neanderthals exist in our own genome to this day. But this shows like actually there were probably several thousand years where these two species existed in the same region.

IRA FLATOW: What was the detective work here? How did scientists figure this out?

RACHEL FELTMAN: So they were able to examine some bone fragments and look at the mitochondrial DNA, so the maternal line of these ancient humans. And they were able to show definitively that these were Homo sapiens in this cave. And in fact, there were no signs of Neanderthals in this particular cave at all.

And what’s cool about that is that there were some particular spear-tip fragments that were found there that scientists have long assumed were created solely by Neanderthals during this time. But this is an indication that Homo sapiens were also making them. So that could actually help them find more caves to maybe examine a bit more closely because maybe there were Homo sapiens there instead of or in addition to Neanderthals.

IRA FLATOW: Hmm. All right. Let’s move on to this next story. It’s really interesting. Most of us are used to typing just about every day, but it turns out now there’s evidence that the old-fashioned way, writing by hand, may be better at improving learning and memory.

RACHEL FELTMAN: Yeah, it could be. There’s still a lot to learn, but basically, they slap some electrodes onto some students heads and had them write words by hand and also type them. And they were looking at what parts of the brain got activated during those two activities.

And handwriting activated like almost the whole brain, and different parts of the brain were talking to each other, like the visual, and sensory, and motor cortices. But typing was a very flat, simple activity in terms of what parts of the brain were lighting up. And the researchers think this is because, when you think about it, writing involves making lots of different movements.

There’s a lot of coordination involved. There’s fine motor. You have to recall how different letters are shaped, and how to make, them and how to make them one against the other in different sequences. So it’s actually very complicated.

And typing is a pretty repetitive motion. So it’s not clear yet. We don’t actually have evidence that this activity translates to better memory, better learning. But there are some other studies that have tried to show that.

So it’s building a body of evidence that writing does lead to better recall. There are a couple caveats. The study did use cursive, and the researchers were quick to point out they don’t actually have evidence that cursive is better for your brain than other forms of writing. They just decided to use cursive because they like cursive. As someone who struggled with cursive as a child and really can’t write it, I appreciate it that they made that clarification.

IRA FLATOW: [LAUGHTER]

RACHEL FELTMAN: And they also pointed out they are not arguing that typing is bad. I think one of the researchers said, obviously, if you’re writing a whole essay, you should type it. Don’t write that by hand unless you really want to. But maybe in terms of writing notes, or journal entries, or things that you really want to recall later, maybe it’s worth trying to write them by hand and see if that makes a difference for you.

IRA FLATOW: They’re not saying to kids, hey, step away from the computers and iPads totally–

RACHEL FELTMAN: Exactly.

IRA FLATOW: –when it comes to–

RACHEL FELTMAN: Yeah.

IRA FLATOW: Right. Right. Right. I’m figuring that our next story is going to give me a new use for that pack of disinfectant wipes left over from COVID because a study found that closing the toilet seat before flushing doesn’t really reduce cross-contamination on bathroom surfaces. Didn’t we think that did? Wasn’t there a study years ago that said, yes, you should do that?

RACHEL FELTMAN: Yeah. So as somebody who’s like written about a lot of poop-related science research over the years, whenever a study like this comes out, people freak out. And I always remind people there are poop particles everywhere.

It’s not just the stuff that comes out of your toilet. So I know that disturbs some people, but microbes are– we can’t get away from them. However, that doesn’t mean you can’t do what you can to limit your toilet spewing as many microbes as possible.

So yeah, these researchers, they basically seeded a toilet with this microorganism that’s really easy to track and identify, and then flushed, and examined the whole room to see where things went. And yeah, unfortunately, it seems like the gaps in a closed toilet seat are plenty for microbes and microdroplets to get out. There’s a lot of air flow that happens when a toilet flushes, so there’s a lot of force.

But the good news for people who are freaked out about this is that they did find that rigorously cleaning a toilet bowl with a brush and an antimicrobial cleaning agent, like Lysol, did reduce the contamination quite a lot. So if you don’t want this to happen in your bathroom, you should use disinfectant in the toilet bowl and the toilet tank, especially if you are sharing space with someone who has norovirus or is otherwise sick with a gastrointestinal ailment.

So yeah, disinfectant does help disinfect. That’s a great takeaway from this study.

IRA FLATOW: Yeah. Well, I moved my towels away from the toilet years ago when we first heard about this, so.

RACHEL FELTMAN: Yeah, it’s fair enough.

IRA FLATOW: This is great news, Rachel. You always bring us great stuff. Thanks for taking time to be with us today.

RACHEL FELTMAN: Thanks so much for having me, Ira.

IRA FLATOW: Rachel Feltman, host of the podcast The Weirdest Thing I Learned This Week.

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