Twice a year, 40 scientists gather together for five days to decide what strains of influenza to vaccinate against for the next flu season. It takes around six months to prepare the vaccine – which usually includes protection against three different strains of flu.

Europe and the US are heading into a flu season that some are warning could be particularly severe this winter. While even as summer approaches in Australia, the country is still registering high numbers of cases after a record-breaking flu season earlier in the year.

So how does the process of deciding on a flu vaccine each year actually work? And does what happens in the southern hemisphere influence the way the virus circulates in the northern hemisphere?

In this episode, we speak to Ian Barr, deputy director for the WHO Collaborating Centre for Reference and Research on Influenza, based at the Peter Doherty Institute for Infection and Immunity, part of the University of Melbourne. Barr is one of those 40 scientists who attend the meetings to decide what strains to focus vaccination efforts on.

This episode was produced by Mend Mariwany, Katie Flood and Gemma Ware. Mixing by Michelle Macklem and theme music by Neeta Sarl. Read the full credits for this episode and sign up here for a free daily newsletter from The Conversation.

If you like the show, please consider donating to The Conversation, an independent, not-for-profit news organisation.

• First human bird-flu death from H5N5 – what you need to know
• Flu season has arrived – and so have updated flu vaccines
• Flu season has started early in the UK – here’s what might be going on

As Pakistanis and Indians struggle with hazardous air quality, in Beijing – a city once notorious for its smog – the air quality is currently rated as good.

Ahead of the 2008 Beijing Olympics, the Chinese government was so concerned about pollution that it introduced temporary restrictions on cars, shut down factories and work on some construction sites. It would take a few more years before the Chinese government implemented a clean air action plan in 2013. Since then, China has achieved a dramatic improvement in its air quality.

In this episode, we speak to Laura Wilcox, a professor at the National Centre for Atmospheric Science at the University of Reading in the UK, to understand how China managed to clean up its air pollution. But Wilcox’s recent research uncovered some unintended consequences from this cleaner air for the global climate: the pollution was actually helping to cool the atmosphere and by taking it away, it may have accelerated global warming.

This episode was produced by Mend Mariwany, Katie Flood and Gemma Ware. Mixing by Michelle Macklem and theme music by Neeta Sarl. Read the full credits for this episode and sign up here for a free daily newsletter from The Conversation.

If you like the show, please consider donating to The Conversation, an independent, not-for-profit news organisation.

• Solar geoengineering: the risks and distractions of trying to reflect sunlight to cool the Earth – podcast
• Delhi: how weather patterns and faraway mountains made this the world’s most polluted megacity
• Cleaner air in east Asia may have driven recent acceleration in global warming, our new study indicates

Since the 1960s, scientists have been developing and honing models to understand how the earth’s climate is changing. One such pioneer of early climate modelling is Syukuro Manabe, who won the Nobel prize in physics in 2021 for his work laying the foundation for our current understanding of how carbon dioxide affects global temperatures. A seminal paper he co-published in 1967 was voted the most influential climate science paper of all time.

In this episode,  we speak to Nadir Jeevanjee, a researcher at the same lab in the National Oceanic and Atmospheric Administration where Manabe once worked, to look at the history of these early climate models, and how many of their major predictions have stood the test of time.

And yet, as climate negotiators gather in the Brazilian city of Belem on the edge of the Amazon for the Cop30 climate summit, the data sources that climate scientists around the world rely on to monitor and model the climate are under threat from funding cuts by the Trump administration.

This episode was produced by Mend Mariwany, Katie Flood and Gemma Ware. Mixing by Eleanor Brezzi and theme music by Neeta Sarl. Read the full credits for this episode and sign up here for a free daily newsletter from The Conversation.

If you like the show, please consider donating to The Conversation, an independent, not-for-profit news organisation.

• How to find climate data and science the Trump administration doesn’t want you to see
• The most influential climate science paper of all time
• 5 forecasts early climate models got right – the evidence is all around you

At dawn on October 28, residents of Rio de Janeiro woke to the sound of gunfire. Battles continued throughout the day in the favelas of Alemão and Penha, as police mounted a huge operation targeting the Commando Vermelho, or the Red Command, one of Brazil’s largest organised criminal gangs.

In the days that followed, as graphic images showed lines of bodies on the streets, it emerged that at least 115 civilians and four police officers had been killed, making it the most violent police operation in Brazilian history.

In this episode, we speak to Robert Muggah, founder of the Institute Igarapé and a research collaborator at the Brazil LAB at Princeton University, about how organised crime become so deeply embedded in Brazil – and if there's a better way to confront it.

This episode was produced by Mend Mariwany, Katie Flood and Gemma Ware. Mixing by Eleanor Brezzi and theme music by Neeta Sarl. Read the full credits for this episode and sign up here for a free daily newsletter from The Conversation.

If you like the show, please consider donating to The Conversation, an independent, not-for-profit news organisation.

• Análise: O crime organizado se tornou o maior negócio do Brasil - e sua mais séria ameaça
• Read more about the Cop30 climate summit in Belem, Brazil
• The rise of Brazil’s fuel mafias and their gas station money laundering machines

In the 16th century, witches and demons weren’t just for Halloween. People were terrified and preoccupied with them – even kings.

In 1590, James VI of Scotland – who was later also crowned James I of England – travelled by sea to Denmark to wed a Danish princess, Anne. On the return journey, the fleet was hit by a terrible storm and one of the ships was lost.

James, a pious Protestant who would go on to sponsor the translation of the King James bible, was convinced he’d been the target of witchcraft. A few years later, James decide to write a treatise called Daemonologie, setting out his views on the relationship between witches and their master, the devil.

Meanwhile, another firm Halloween favourite – ghosts – had fallen out of favour in the wake of the Protestant Reformation because they were seen as a hangover from Catholicism.

In this episode, Penelope Geng, an associate professor of English at Macalester College in the US who teaches a class on demonology, takes us back to a time when beliefs around witches, ghosts and demons were closely tied to religious politics. She explains how these beliefs have come to influence the way witches and ghouls have been portrayed in popular culture ever since.

This episode was produced by Mend Mariwany and Katie Flood with mixing by Eleanor Brezzi. Theme music by Neeta Sarl. Gemma Ware is the executive producer. Read the full credits for this episode and sign up here for a free daily newsletter from The Conversation.

If you like the show, please consider donating to The Conversation, an independent, not-for-profit news organisation.

• From printing presses to Facebook feeds: What yesterday’s witch hunts have in common with today’s misinformation crisis
• Samhain: the true, non-American origins of Halloween
• What’s the difference between ghosts and demons? Books, folklore and history reflect society’s supernatural beliefs

One American company called Strategy owns more than 3% of all bitcoin in existence. In August 2020, its executive chairman, Michael Saylor, pioneered a new business model where publicly listed companies buy cryptocurrency assets to hold on their balance sheet.

More than 100 other public companies have since followed Saylor’s lead and become bitcoin treasury companies, together holding more than $114 billion of bitcoin. There’s been a new rush into crypto treasury assets in 2025 following the general crypto enthusiasm of the new Trump administration.

But holding bitcoin assets also comes with some big risks, particularly given the volatility of cryptocurrency prices, and the share prices of some of these companies are now coming under pressure.

In this episode, we speak to Larisa Yarovaya, director of the centre for digital finance at the University of Southampton in the UK, about whether bitcoin treasury companies are the future of corporate finance, or another speculative bubble waiting to burst.

This episode was produced by Mend Mariwany and Gemma Ware with assistance from Katie Flood. Mixing by Michelle Macklem and theme music by Neeta Sarl. Read the full credits for this episode and sign up here for a free daily newsletter from The Conversation.

If you like the show, please consider donating to The Conversation, an independent, not-for-profit news organisation.

• Cryptocurrency’s transparency is a mirage: New research shows a small group of insiders influence its value
• Bitcoin: why a wave of huge companies like Tesla rushing to invest could derail the stock market
• Could digital currencies end banking as we know it? The future of money

As one of the birthplaces of the industrial revolution, the River Mersey in northern England is no stranger to pollution flowing into its waters. Now it's got a new problem: monitoring shows the amount of forever chemicals, also known as PFAS, entering the Mersey catchment area is among some of the highest in the world.

In this episode we speak to water scientist Patrick Byrne at Liverpool John Moores University in the UK about why so many per- and polyfluoroalkyl substances (PFAS), are still making it into our rivers, many from sources that are lying hidden. Identifying these sources of pollution, can help prioritise how to clean them up.

This episode was produced by Mend Mariwany, Katie Flood and Gemma Ware. Sound design and mixing by Michelle Macklem and theme music by Neeta Sarl. Read the full credits for this episode and sign up here for a free daily newsletter from The Conversation.

If you like the show, please consider donating to The Conversation, an independent, not-for-profit news organisation.

• You can be exposed to PFAS through food, water, even swimming in lakes – new maps show how risk from ‘forever chemicals’ varies
• Australia has banned 3 ‘forever chemicals’ – but Europe wants to ban all 14,000 as a precaution
• How I tracked the biggest hidden sources of forever chemical pollution in UK rivers – new study

Back in the 1980s, when Shimon Sakaguchi was a young researcher in immunology, he found it difficult to get his research funded. Now, his pioneering work which explains how our immune system knows when and what to attack, has won him a Nobel prize.

Sakaguchi, along with American researchers Mary Brunkow and Fred Ramsdell, were jointly awarded the 2025 Nobel prize in physiology or medicine for the work on regulatory T-cells, known as T-regs for short, a special class of immune cells which prevent our immune system from attacking our own body.

In this episode Sakaguchi tells The Conversation about his journey of discovery and the potential treatments it could unlock.

This episode was produced by Mend Mariwany, Katie Flood and Gemma Ware. Sound design and mixing by Michelle Macklem and theme music by Neeta Sarl. Read the full credits for this episode and sign up here for a free daily newsletter from The Conversation.

If you like the show, please consider donating to The Conversation, an independent, not-for-profit news organisation.

• Metal-organic frameworks: Nobel-winning tiny ‘sponge crystals’ with an astonishing amount of inner space
• Nobel physics prize awarded for pioneering experiments that paved the way for quantum computers
• How does your immune system stay balanced? A Nobel Prize-winning answer
• Nobel medicine prize: how a hidden army in your body keeps you alive – and could help treat cancer

As Donald Trump gives oxygen to unproven theories about what might be behind a recent rise in autism cases, experts repeatedly point to the changing nature of how autism is diagnosed and viewed.

A key moment in the history of autism diagnosis was the publication in 1994 of a new version of the Diagnostic and Statistical Manual of Mental Disorders. It's a reference book of psychiatric conditions and how to diagnose them, used by psychiatrists and psychologists around the world.

In this episode, Andrew Whitehouse, a professor of autism research at the University of Western Australia, explains why this shift in autism diagnosis happened in the 1990s, what impact it had, and what it's meant for the support autistic people get.

This episode was produced by Katie Flood, Mend Mariwany and Gemma Ware. Sound design and mixing by Michelle Macklem and theme music by Neeta Sarl. Read the full credits for this episode and sign up here for a free daily newsletter from The Conversation.

If you like the show, please consider donating to The Conversation, an independent, not-for-profit news organisation.

Donald Trump is not letting up pressure on the US Federal Reserve. He's taken efforts to fire one of its governors, all the way up to the US Supreme Court.

Trump's clash with the Fed echoes pressure that Richard Nixon put on the central bank in the 1970s to lower interest rates. In this episode, Cristina Bodea, professor of political science at Michigan State University, why that moment – and the inflation spike that followed – became a cautionary tale about what can happen if politicians threaten the independence of central banks.

This episode was written and produced by Katie Flood and Gemma Ware with assistance from Mend Mariwany. Sound design and mixing by Eloise Stevens and theme music by Neeta Sarl. Read the full credits for this episode and sign up here for a free daily newsletter from The Conversation.

If you like the show, please consider donating to The Conversation, an independent, not-for-profit news organisation.