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The following is a transcript of the podcast episode:

Rachael Robertson: Hey everybody, welcome to MedPod Today, the podcast series where 麻豆传媒 reporters share deeper insight into the week's biggest healthcare stories. I'm your host, Rachael Robertson.

Today, we are talking with Kate Kahn about some exciting research out of the International AIDS Conference. Then, Jennifer Henderson will tell us about the risks of swimming in dirty water. Yeah, we're talking about you, Olympic swimming in the Seine. Last up, Sophie Putka will share some reporting on whether slushies are risky for small children.

But first, let's get into the latest AIDS research.

The International AIDS Conference – AIDS 2024 – just wrapped up in Munich. A lot of promising research was presented, and 麻豆传媒's infectious disease reporter Kate Kahn is here to tell us about two items that made a big splash. One is a case report about the "next Berlin patient," and the second are the results from the PURPOSE 1 trial.

So Kate, tell us about the next Berlin patient and why this case drew so much attention at the conference.

Kate Kahn: Yeah, so the next Berlin patient is the world's seventh person apparently cured of HIV following a stem cell transplant. Now, the earliest case of a person being cured of HIV this way was in 2007, and that person was known as the "first Berlin patient."

But the next Berlin patient was diagnosed with HIV in 2009 and then diagnosed with acute myeloid leukemia in 2015, and at that time, he received a stem cell transplant as treatment for his cancer. He stopped taking antiretroviral therapy – ART – in 2018, and has had no detectable HIV RNA in his blood or tissue biopsy since, and he's been in drug-free remission for more than 5 years at this point.

Robertson: That is amazing. What makes this case stand out from the handful of other people who have apparently been cured of HIV?

Kahn: Yeah, so the reason this case is so interesting is it's only the second case of HIV cure where the stem cell donor was not homozygous for CCR5-delta 32. CCR5 is a receptor that allows HIV to enter cells, and being homozygous for the CCR5-delta 32 mutation essentially confers immunity to HIV, but it's a really rare mutation, so there are very few donors that have it. The next Berlin patient's donor was heterozygous for CCR5, meaning the donor only had one delta 32 mutation and could probably make some functional CCR5.

But interestingly, last year, there was another report of a person with HIV, referred to as the "Geneva patient," who received a stem cell transplant that was from a donor with wild type CCR5, meaning he had no delta 32 mutations, and that person has been in drug-free remission for about 32 months. Now, both of these cases are really calling into question the role of CCR5 and whether HIV readmission or cure is possible independent of donor CCR5 status and what other factors may be at play, which at this point remains something of a mystery, although a high suppression of HIV with pre-exposure prophylaxis – PrEP – or the drugs given for transplantation might contribute to remission.

Robertson: Got it. Let's move on to the results of the PURPOSE 1 trial, which was one of the most anticipated presentations at the conference. What would you say the key take home points were about this trial?

Kahn: Yeah, so researchers found that twice yearly injections with the antiretroviral drug lenacapavir was very effective in preventing HIV infection in South African and Ugandan women. In fact, there were zero new HIV infections among women and adolescent girls who received lenacapavir, compared with 16 infections among those who took daily oral PrEP with an F/TDF regimen, and 39 infections among those who took an F/TAF regimen.

And it's a really important study, because women, especially those in high-risk countries, face a lot of barriers to oral PrEP adherence, and this is a twice yearly injectable. But it's also important to understand these incredibly encouraging results are no guarantee that women who would benefit the most from lenacapavir will actually have access to it. Lenacapavir currently costs about $43,000 per year in the U.S., so cost alone might limit its access in high-risk countries. And one area of uncertainty that's really important is whether or not lenacapavir is safe during pregnancy. There just isn't enough safety data at this point to make recommendations for or against its use during pregnancy and breastfeeding, and that's a key issue that may limit its use in women of childbearing age.

Robertson: Awesome. Well, thank you so much for your reporting on this and for making your MedPod debut, Kate.

Kahn: Yeah, thank you, Rachael. It's a pleasure.

Robertson: You've probably heard that some Olympic athletes are expected to swim in the Seine River in Paris. But earlier this week, training for the swimming portion of triathlon events was canceled for two consecutive days and the actual events were postponed. The cause? Bacteria in the water. Jennifer Henderson is here to tell us more.

Jennifer, what is going on with water quality in the Seine?

Jennifer Henderson: So the issue is not a new one. Swimming in the Seine has been banned for a century. However, before the Olympics began, France took measures to clean up the body of water. Recently, though, heavy rains returned high levels of bacteria to the Seine, and officials have continued to monitor the river's water quality. So 麻豆传媒 asked an infectious disease expert to weigh in on the hazards that could be lurking there and what the risks to athletes may be.

Bruce Hirsch, MD, of North Shore University Hospital in New York, pointed to high levels of E. coli in the water. Once the concentration is above 900 colony-forming units per 100 milliliters of water, it's considered unhealthy and potentially risky, he explained.

Robertson: Yikes. Okay, so what are the risks to athletes swimming in the Seine?

Henderson: Hirsch said that a significant source of E. coli is in the lower intestine of people and animals, and that it's certainly not alone there. Other germs of concern could include Cryptosporidium and Giardia as well as Salmonella and Shigella. Potential health risks of swimming in contaminated water include gastrointestinal infection with symptoms including diarrhea, nausea, and abdominal cramping. He said: "It's very easy to swallow small amounts of water when swimming, especially when exerting oneself and swimming for a long time."

There's also the potential risk of infections on the surface of the body – for instance, through a scratch or a wound, he noted, and people may also experience eye, ear, or upper airway irritation. "Not everyone is going to be sick, but to ask people to participate in a physical contest in which they're being asked to stretch themselves and there's a good chance that a number of these people can get seriously ill, I don't think that's responsible or appropriate," Hirsch said. Canceling or postponing events and monitoring the water quality are appropriate and cautious, he noted.

Robertson: Okay, are these water quality issues specific to the Seine?

Henderson: So Hirsch said it's not just the Seine that faces potential safety issues. And climate change has heightened some concerns regarding pathogens and water, he noted. For instance, algae blooms can occur when algae overgrows in warm weather and causes a film on the surface of water. These circumstances can lead to skin and airway issues, he explained. Generally speaking, it's important to understand that "immediately after a severe rainstorm, our waterways may be contaminated," Hirsch said.

Robertson: I don't think I'm going to be swimming in the Seine anytime soon. Thanks for this report, Jennifer.

Henderson: Thank you, Rachael.

Robertson: Now we'll hear from Sophie Putka about an ingredient sometimes used in a classic summer treat – and why health regulators in the U.K. cracked down on it after two young children were hospitalized. A pediatric emergency physician in Florida recently warned her followers to limit how much of it to serve to kids. But was she right to raise the alarm?

Sophie, can you tell us – what is this mystery ingredient and what is it used in?

Sophie Putka: Sure. So in the U.K. last year, two very small children came down with some severe symptoms – unconsciousness, seizures – after drinking frozen slushies. And these apparently weren't the huge ones that we have here in the U.S., either, according to the news reports. But it turned out the kids' symptoms were consistent with what's known as "glycerol intoxication." So glycerol, which is also called glycerin, is a sugar alcohol that's actually a really common additive in tons of products, and yes, it's sometimes added to frozen treats like slushies. It's kind of this viscous liquid that can sweeten, it retains moisture, it keeps things at a certain consistency, and it can prevent ice crystals from forming. A few experts I talked to told me that generally it's not something we really need to worry about as adults.

Robertson: Okay, so adults don't have to worry, but kids might. Where do we run into these problems with glycerin?

Putka: You're absolutely right. So we run into problems when children, generally under the age of 4, ingest too much glycerin. The doctor who originally posted about the issue, Meghan Martin, MD, of Johns Hopkins All Children's Hospital in Florida, said in her video that small kids can get headache, nausea, vomiting, diarrhea, and agitation from too much glycerin, and in the worst case scenario, they can go into shock, lose consciousness, and have hypoglycemia – kind of like what happened in the U.K. But Steven Marcus, MD, the former director of the New Jersey Poison Control Center, reminded me of this core concept in toxicology: "The dose makes the poison" – and usually this is by body weight.

So both England and Scotland, after a handful of these cases with the slushies, put out some new guidance around glycerin in slushies. According to Scotland's version, 125 mg/kg of body weight per hour would be the lowest dose of glycerol associated with negative health effects. Children under 4 happen to be pretty small, so they shouldn't have large amounts of slush. But it's actually kind of tough to know what concentration of glycerin is actually used in various brands of slushies. So to make things safer, they told slushie makers to limit glycerol to the minimum amount needed for a "slush" effect, and to include a warning that's visible to consumers against slushies for children 4 and under, and they recommended against free refills where children under 10 are going to be served.

Robertson: That sounds reasonable, though, I'm sure not to the kids under 10. Why aren't we seeing anything similar to that here in the U.S.?

Putka: That's a really good question. The doctor who originally posted about slushies did it for the much loved free Slurpee day at 7-11 and said that their Slurpees do actually contain "sugars" which she took to include sugar alcohols like glycerol or glycerin. I looked up the ingredients and 7-11 does not list glycerin specifically, like she said, so it's still not clear. I looked at some other big slushie brands, like Sonic slushies and Icees, and they don't seem to contain glycerin. Both of them list good old fashioned high-fructose corn syrup. And a few brands of ice cream, though, like Coldstone, do use glycerol in a handful of their flavors. But as far as other frozen desserts go, I really couldn't find much.

I reached out to the FDA to ask them about glycerin, and they confirmed that we don't, in fact, have what's known as an "Acceptable Daily Intake" amount for glycerin, because of what they said was "evidence of the ingredient's safety at levels well above the amounts needed to achieve the desired effect (such as sweetening) in food." They also don't have any specific written warning like the U.K.

The experts I spoke to said they hadn't heard of any bad effects from slushies here in the U.S., and they were kind of stumped. They couldn't imagine it being added in high enough levels to cause problems. So as far as why they were doing that in the U.K., we may never know, but for now, our experts said, just use moderation when it comes to the frozen treats. One small cup for a small kid is probably enough for them.

Robertson: Thanks, Sophie.

Putka: Thanks, Rachael.

Robertson: And that is it for today. If you like what you heard, please leave us a review wherever you listen to podcasts (, ), and hit subscribe if you haven't done so already. We will see you again soon.

This episode was hosted and produced by me, Rachael Robertson. Sound engineering by Greg Laub. Our guests were 麻豆传媒 reporters Kate Kahn, Jennifer Henderson, and Sophie Putka. Links to all of their stories are in the show notes.

MedPod Today is a production of 麻豆传媒. For more information about the show, check out medpagetoday.com/podcasts.

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