It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Saturday, September 20, 2025
Scenario projections of COVID-19 burden in the US, 2024-2025
In this decision analytical modeling study of COVID-19 burden in the U.S. in 2024 to 2025, ensemble projections suggested that although vaccinating high-risk groups had substantial benefits in reducing disease burden, maintaining the vaccine recommendation for all individuals had the potential to save thousands more lives. Despite divergence of projections from observed disease trends in 2024 to 2025—possibly driven by variant emergence patterns and immune escape—averted COVID-19 burden due to vaccination was robust across immune escape scenarios, emphasizing the substantial benefit of broader vaccine availability for all individuals.
Corresponding Author: To contact the corresponding author, Sung-mok Jung, PhD, email sungmok@ad.unc.edu.
Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.
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Menstrual cycle and long COVID: A relation confirmed
Women suffering from long COVID have a greater risk1 of experiencing abnormal uterine bleeding2. The symptoms of the illness intensify during the perimenstrual and proliferative phases of the menstrual cycle, notably fatigue, headaches, and muscle pain. This bidirectional relationship between long COVID and menstrual disorders has been revealed by a French-British research team co-led by a CNRS researcher3. An inflammatory reaction is suspected of being behind this connection, after the discovery of an immune cell cluster in the endometrium of the patients receiving treatment. No abnormalities were detected in relation to ovarian hormones.
These conclusions, which were just published in Nature Communications, are based on a combination of three approaches: a study conducted among 12,187 British women; follow-up care for 54 women suffering from long COVID for three months; and analysis of blood and endometrial samples.
As long COVID affects 3-7% of the world’s population4, and is twice as prevalent among women than men, this novel study paves the way for new therapeutic prospects. It also underscores the importance of considering the menstrual cycle in long COVID biomarkers, as well as the need to develop therapies specifically adapted to women.
Notes
1 – Outside of a long COVID context, “abnormal” uterine bleeding already affects one in three people worldwide, causing anaemia and major socioeconomic impact.
2 – Compared to a control group, long COVID is associated with reporting more abundant and longer periods, in addition to bleeding between cycles, contrary to acute COVID.
Researchers at the ESRF - the European Synchrotron-, together with CNRS, ENS Lyon and the Institute of Marine Research in Norway, have unveiled how Atlantic Bluefin tuna transforms the toxic form of mercury into less harmful forms. Their study, published in Environmental Science & Technology, shows that the tuna’s edible muscle contains not only toxic methylmercury, but also mercury bound in stable, non-toxic compounds.
Mercury contamination in seafood is a global health concern. Mercury (Hg) originates both from natural sources like volcanoes and forest fires and from human activities such as coal burning, gold mining, and industrial waste incineration. Bacteria convert it into toxic methylmercury, which is biomagnified within food webs. Because tuna are top predators, eating many smaller contaminated fish, mercury accumulates in their bodies over time.
However, not all mercury is equally toxic, its chemical form makes a big difference. A study led by Alain Manceau, researcher emeritus CNRS/ENS Lyon, scientist at the ESRF, who has spent years studying how animals detoxify mercury, recommends how the mercury content should be measured. “When evaluating the level of toxicity, we should do so by measuring the concentration of methylmercury, which can be done routinely today, instead of total mercury”, he explains. "Otherwise, we include forms of mercury that are sometimes present in fish but are harmless to the human body."
Bluefin tuna detoxify the toxic form of methylmercury
Using the ESRF’s intense X-ray beams, the team tracked how mercury is processed inside Atlantic Bluefin tuna. They discovered that, unlike toothed whales and apex seabirds, where detoxification occurs mainly in the liver, Atlantic Bluefin tuna rely primarily on the spleen to break down methylmercury. The process of detoxification takes place due to the interaction between selenium – an essential nutrient found in seawater – and mercury, as selenium binds mercury into stable mercury–selenium complexes, which are far less toxic, if at all. High-trophic marine predators detoxify methylmercury through a series of reactions involving reduced selenium in the form of a prominent selenoprotein (Selenoprotein P).
To obtain these results, Alain Manceau and Pieter Glatzel, an ESRF scientist, used a synchrotron technique called high-energy-resolution X-ray absorption spectroscopy. The team found that part of mercury in edible muscle of Atlantic Bluefin tuna occurs as a tetraselenolate complex (Hg(Sec)4), which is arguably not toxic, since this complex transforms into inert mercury selenide in the spleen. “The reason why the muscle has no mercury selenide is simply because the mercury concentration is not that high in this tissue to begin with”, adds Manceau.
Different tuna species, different concentrations
The Atlantic Bluefin tuna investigated were caught along the Norwegian coast. “Samples of such large individuals, which can weigh up to 300 kg, are difficult to get, but being high trophic predators, they make key model organisms to study” explains Martin Wiech, scientist from the institute of Marine Research.
The Atlantic Bluefin tuna is a high trophic predator, like Bigeye tuna, so the results of this research cannot be extended to lower trophic tuna species, which contain much less mercury. The smaller tuna species, such as albacore and skipjack, typically found in tuna cans, are much less contaminated.
This study highlights the need for more precise testing of seafood, distinguishing between toxic methylmercury and less reactive mercury–selenium complexes, to provide consumers with better-informed food safety recommendations. “One generally assumes that all mercury in fish is methylated” concludes Manceau. “While this is usually the case, our results show that up to a quarter of the mercury present in the edible muscle of bluefin tuna is in less harmful forms. This proportion reaches 90% in marlin, also known as makaire. Health risks, therefore, depend not only on the total amount of mercury, but also on its chemical form.”
Reference:
Manceau, A., et al., Demethylation Pathway of Methylmercury in the Spleen and Peripheral Organs of Bluefin Tuna – Implications for Fish Consumers, Environmental Science & Technology, 18 September 2025. DOI : https://doi.org/10.1021/acs.est.5c08815
Alain Manceau, researcher emeritus CNRS/ENS Lyon, scientist at the ESRF, during experiment at the ESRF, the European Synchrotron
Posidonia seagrass meadows, veritable underwater forests, play a major ecological role. Under constant pressure from human activity, scientists are looking for ways to ensure their survival, in particular by carrying out restoration campaigns. A study conducted by the University of Liège at the marine and oceanographical rsearch station STARESO (Calvi, Corisa) reveals that the transplantation method directly influences the root microbiome, which is essential for the survival of the plants. These results pave the way for more effective and sustainable restoration techniques.
Often compared to terrestrial forests, Posidonia oceanica seagrass meadows form off the coast of the Mediterranean. These ecosystems act as environmental sentinels, stabilising the seabed, storing carbon and harbouring exceptional biodiversity. Unfortunately, scientists have been observing a decline in their population for many years due to coastal urbanisation, boat anchoring and climate change.
To halt this decline, researchers are experimenting with transplanting cuttings. "Until now, efforts have focused mainly on their visible survival, i.e. root recovery and leaf growth," explains Arnaud Boulenger, a PhD candidatein oceanography at ULiège (Belgium). However, the study we conducted at STARESOreveals that the health of seagrass beds also depends on an invisible network of microorganisms associated with the roots." It is therefore not enough to simply replant the seagrass meadows; we must also ensure the good health of their microbiome!
By testing three transplantation techniques – metal staples, coconut fibre mats and potato starch structures – the team showed that the choice of substrate profoundly changed the composition of the microbiome. "Staples, which allow direct contact with the sediment, promote the establishment of key bacteria such as Chromatiales and Desulfobacterales, which are essential for the sulphur and nitrogen cycles," the researcher explains. Conversely, the other methods delay this beneficial colonisation."
Scientists highlight that restoration methods must now incorporate this microbiological dimension, as these bacteria play a direct role in plant resilience. "These results are groundbreaking," says Sylvie Gobert, oceanographer. "This is the first time that a study has demonstrated in situ the importance of the microbiome in the success of Posidonia transplantation. The results we have obtained open up concreteperspectives, such as the inoculation of beneficial bacteria or the design of supports that facilitate root-sediment interaction."
Restoring a seagrass bed is therefore much more than just replanting cuttingsunderwater. It means recreating an entire ecosystem, both visible and invisible, in which bacteria play a crucial role. As Arnaud Boulenger sums it up, "it's a bit like replanting a forest, while also ensuring that the soil that nourishes it is brought back to life."
The three transplantation techniques used in this study: (A) metal staple, (B) coconut fibre mat, and (C) potato starch structure.
The Red Sea, circled by desert landscapes, is home to marine life accustomed to the water’s bathtub-like temperatures—often reaching 85 to 90 degrees Fahrenheit in the summer. But in the past three years, marine heat waves have made the Red Sea even hotter. Rising ocean temperatures, there and around the world, have been devastating for many sea creatures, including an iconic ocean duo: clownfish and anemones.
A new paper from a Boston University–led research team finds that this extreme heat has caused a breakdown in the mutualistic relationship of clownfish—also called anemonefish— and anemones and has resulted in a population collapse in the central Red Sea.
This pair forms one of the most widely recognized mutually beneficial relationships in the ocean—thanks to Finding Nemo. They’re adapted to work as a team to get nutrients and for protection. Anemones also have a symbiotic relationship of their own—with a microscopic algae called zooxanthellae, the same algae that pairs with coral. Just like corals, anemones expel the algae from their tissue during periods of unusually high heat, causing them to bleach. The researchers found that prolonged bleaching can not only lead to the death of the anemone and the anemonefish, but collapses the entire mutualistic system.
“We always hope that anemones and clownfish groups survive bleaching events, as they have over and over again in the last 10 years, but it hit a point where it was too extreme,” says Morgan Bennett-Smith (GRS’25,’27), a PhD candidate in BU’s Marine Evolutionary Ecology Laboratory and lead author of the paper. He has studied anemones in the Red Sea for the last decade and has witnessed firsthand how exceedingly high temperatures have pushed the anemones and clownfish past the temperature threshold they can tolerate.
The research, which started when Bennett-Smith was studying at King Abdullah University of Science and Technology in Saudi Arabia, focused on Red Sea clownfish (Amphiprion bicinctus) and their host sea anemones (Radianthus magnifica) on three central Saudi Arabian Red Sea reefs from 2022 to 2024—coinciding with a 2023 marine heatwave. According to Bennett-Smith, the monitored anemones were bleached for about six months during that time. As a result, the paper estimates that 94 to 100 percent of the clownfish died, and 66 to 94 percent of the anemones.
“It’s especially painful because the Red Sea is a place many researchers have been hoping and hypothesizing is a thermal refuge,” he says, meaning that organisms there would be protected from the impacts of climate change due to its location and already hot temperatures. “The fact that even this thermal refugium is collapsing in different ways is especially horrific. It’s not turning out to be the safe haven we thought it was.”
To a clownfish, anemone bleaching is a catastrophe—their once safe home turns white, exposing them to dangers lurking in the surrounding reef. Under normal conditions, clownfish are camouflaged and protected underneath the swaying, stinging tentacles of an anemone, which are related to jellyfish. The clownfish secrete a mucus that shields them and their eggs from getting stung, so when they attract a predator fish to the anemone, it gets zapped and eaten. Human-caused climate change has heated the ocean to new extremes, and has started to unravel the mutualistic relationships that sustain underwater environments, like those between algae and corals, algae and anemones, and anemones and clownfish.
“Historically, anemones have bleached relatively little compared to corals, but now we’re getting up to levels where the anemones are bleaching, and that results in a catastrophic breakdown in the mutualism with the anemonefishes that everybody knows and loves," says Peter Buston, a BU College of Arts & Sciences associate professor of biology,one of the senior authors on the paper. “We’re seeing nearly a 100 percent die-off in a population of fish in response to a heating event,” says Buston, who leads the Marine Evolutionary Ecology Laboratory. “This should be a big warning for ourselves as well.”
From the Wild to the Lab
Bennett-Smith didn’t set out to study anemone bleaching or the effects of climate change (he was interested in studying the mutualism between anemones and other sea creatures), but he was intrigued when he first observed a bleached anemone in the Red Sea in 2018. At the time, it was an extremely uncommon occurrence. “Since then, year after year, we keep running into worse and worse bleaching events,” he says. Now it’s the main theme of his research at BU. In Buston’s lab, Bennett-Smith and a team of BU students are investigating these dynamics to identify what exactly is causing the population declines.
“We’re interested in figuring out why the fish disappear and die shortly after the bleaching occurs,” says Buston, who is also CAS associate dean of the faculty for the natural sciences. “This mutualism is protecting the fish from predation, so what is happening post-bleaching that leaves the fish exposed? We have a suite of hypotheses that we’re testing in the lab.”
Their first hypothesis is that the fish become more conspicuous—these bright orange fish get exposed against an unnatural white background. They’ve also found that the behavior of the fish changes when their anemones bleach, with more of the clownfish getting into conflicts that leave smaller fish outside of the anemone. The team, in collaboration with colleagues at Harvard University, has also done preliminary testing on the anemones’ stinging cells and found that they don’t fire as well when bleached. In the lab, they’re able to mimic the conditions that lead to bleaching, and study the effects up close.
“There’s a lot going on; increased conspicuousness, increased time outside of the anemones, increased conflict between the fish, and reduced protection from the anemones,” Buston says. “These anemonefish become sitting ducks. They’re not great swimmers and don’t stray from their anemones, so they presumably get taken off by predators.”
Even if wild anemones recover from the bleaching, once the anemonefish are gone, they become much more vulnerable to their own predators, like butterflyfish, who feed on anemones.
“Anemones aren’t as well studied compared to coral, so there’s a lot to unravel,” Bennett-Smith says.
As a continuation of the work in the Red Sea, the team will soon be reporting on similar heating events off the coast of Papua New Guinea, where the bulk of Buston’s research is done. His students travel there multiple times a year to study different aspects of the anemonefish life cyle—like parental care, growth changes, and other dynamics in the small fish colonies. The anemones in the waters of Papua New Guinea have also experienced heating events and bleaching, resulting in noticeable declines and changes to the clownfish. Earlier this year, Buston, Bennett-Smith, and collaborators from Newcastle University in the United Kingdom found that a wild population of clownfish in Papua New Guinea shrink to survive heat stress.
“I’ve studied anemonefishes for a long time, and unavoidably, I and all my students now study them in the context of climate change,” Buston says. “You get enough of these local extinction events, and it ultimately leads to complete extinction.”
Losing these important species has cascading effects on the reef, their paper on the Red Sea points out. The authors call for surveys in other regions of the Red Sea, as well as worldwide, to evaluate their conservation status at large. The hope, according to Bennett-Smith, is that local experts can strengthen conservation and restoration efforts to protect the areas in need, before it’s too late.
The same Radianthus magnifica, in November 2023, show striking changes in the anemone and reef caused by the 2023 heatwave-resulting in the anemone and reef to lose its bright colors.
Credit
Morgan Bennett-Smith
This work received funding from the National Science Foundation. Complete information on authors and funders is available in the published paper.
