Despite heroic efforts to vaccinate against this crippling disease, why does it persist? The fight to eradicate polio is an amazing story: It began with a grassroots movement in the United States and led to a global campaign to wipe out a disease that can cause paralysis and even death. There is no cure, but countless cases have been prevented by an extraordinary campaign to vaccinate every child aged five and under. It’s an operation that requires access to some of the poorest and most remote regions of the world. But polio was supposed to have been eliminated by the year 2000. Nearly two decades later, new cases are still springing up. Why? Neal Razzell examines the challenges and the triumphs in the effort to rid the world of polio.

Donald Trump is threatening to withdraw the US from Nato while the French President Emmanuel Macron has called it “brain dead”. Charmaine Cozier asks if the 70-year-alliance can survive? She speaks to Jacob Heilbrunn from The National Interest think tank – a right of centre foreign policy think tank based in Washington; Fabrice Pothier - senior defence consulting fellow at the International Institute for Strategic Studies and former Nato policy planning director; Sara Bjerg Moller, assistant professor of international security at the School of Diplomacy and International Relations, Seton Hall University in the US; Elisabeth Braw, senior research fellow, RUSI's Modern Deterrence projectProducer: Helen Grady(Photo: President Macron, PM Boris Johnson and Canada's PM Justin Trudeau at the Nato summit reception. Credit: Nato TV/AFP/Getty Images)

Excluding dictators and royalty, there are around 2,000 people in the world who are billionaires. Some inherit wealth while others might build fortunes through inventions, businesses or investments. Some say individuals holding onto extreme amounts of money is wasteful because it could be diverted to other areas that would benefit more people such as education and healthcare. Others reason than some billionaires should keep what they have because they drive economic growth and inspire others to innovate. Are billionaires the right focus or should attention move to the systems and processes that enable them to make and keep huge amounts of money? Experts: Dr Paul Segal Roxanne Roberts Caroline Freund Will WilkinsonPresenter: Celia Hatton Producer: Charmaine Cozier Researcher: Diane Richardson(Photo: Billionaire Kylie Jenner arrives at the 2019 Met Gala in New York City. Credit: Karwai Tang/Getty Images)

An estimated 2.6 billion people use social media, but in the online world not everything is what it seems. Fake accounts and automatic programmes can be used to spread disinformation and influence political narratives. We hear from experts across the world about how elections have been fought, and won, with the help of this electronic – and sometimes not so electronic – army. In a world where social media expansion shows no signs of slowing – how do we protect our elections from social media manipulators? Presenter: Tanya Beckett Producers: Lizzy McNeill & Helen GradyExperts: Samantha Bradshaw Natashya Gutierrez Idayat Hassan Ben Nimmo

A year ago more than a quarter of a million people took to the streets across France, in what became known as the “gilets jaunes” protests. They began as a reaction to an increase in fuel tax - a tax which was supposed to help the environment, but which the protesters said meant they could no longer afford to drive their cars or get to work.These were the first high profile demonstrations against policies designed to tackle climate change, but they put a spotlight on a sense of unrest that has spread far beyond France.So if it is widely accepted that climate change is a real threat, why is there a backlash against climate policies?Contributors include:Jacline Mouraud - Original member of the “gilets jaunes” Matias Turkkila - Editor of the Finns Party Carol Linnitt - Co-founder of The Narwhal Simone Tagliapietra - Research Fellow at Bruegel think tankPresenter: Tanya Beckett Producers: Beth Sagar-Fenton & Josephine Casserly(Yellow Vests (Gilets jaunes) protest in France against a diesel tax increase, justified as an anti-pollution levy. Credit: Xavier Leoty /Getty Images.)

If there was a serious illness that we knew thirty percent of us would experience in our lives, wouldn’t we do everything in our power to address it? Well research suggests that one in three of us will experience a serious mental health problem at some point in our lives; it’s a topic many are uncomfortable about discussing but one that shows no signs of going away. Slowly we’re beginning to learn more about which factors cause anxiety and depression but old prejudices are hard to come overcome so – what can we do about the world’s mental health problem? Presenter: Celia Hatton Producer: Lizzy McNeill Researcher: Helen GradyExperts: Vikram Patel Shekhar Saxena Sir Graham Thornicroft Grace Ryan(image: Earth sunrise in space. Credit Getty Images)

In September 2019 violence broke out in the city of Johannesburg. Many people were beaten, at least 12 were killed, and shops were looted and burned down. The perpetrators were mainly poor black South African men, and those attacked were predominantly immigrants from other African countries and from Asia. This just the latest in a long line of xenophobic attacks in the country. In 2015 the army was even deployed to deter further unrest. Immigrants are often subject to threats on social media, and some have even voluntarily returned to their home countries in response. But in the country once labelled “the rainbow nation”, why are foreigners so often subject to violence?We hear from: Kimberly Mutandiro – freelance journalist Dr Alex Hiropoulos - Assistant Professor of Criminal Justice at California State University, Stanislaus Dr Suren Pillay - Senior Researcher at the Center for Humanities Research, University of Western Cape Dewa Mavhinga - Southern Africa Director, Human Rights WatchPresenter: Victoria Uwonkunda Producer: Beth Sagar-Fenton Researcher: Lizzy McNeill(A woman sings as she holds a banner during a march against the recent rise of xenophobic attacks in South Africa. Credit: Michele Spatari /Getty Images)

This month activists all over the world have taken over city centres, demanding urgent action to halt climate change. They say we need to eliminate all carbon emissions by 2025. Most people think that’s impossible. But scientists are warning that if we want to stop global warming, we need to cut our CO2 emissions fast. So how soon can the planet achieve carbon zero? Helen Grady speaks to: Chukwumerije Okereke, professor in Environment and Development at Department of Geography and Environmental Science, University of Reading and director of the Centre for Climate Change and Development, Alex Ekwueme Federal University (AE-FUNAI), Ndufu-Alike, Ebonyi state, Nigeria; Mercedes Maroto-Valer, Director of the Research Centre for Carbon Solutions at Herriot Watt University in Edinburgh, Scotland; Roger Pielke Junior, Professor at the University of Colorado; Rachel Moncrief, deputy director at the International Council on Clean TransportationProducer: Beth Sagar-Fenton(Photo: Wind turbines in California USA. Credit: David McNew/Getty Images)

Turkey’s push to clear the Kurds from its border with Syria has brought howls of betrayal. Many Kurds believed the Americans would protect them, after they’d defeated the so-called Islamic State terror group together. But this is just the latest of the dozens of conflicts in which the Kurds have been involved over the past few decades. Why can’t they find peace? Is it their fault? Should the regimes they live under take responsibility? Or does the blame lie further back in history?We hear from: Dr Afshin Shahi - Lecturer in Middle East politics and International Relations at Bradford University Dr Gönül Tol - Director of Center at The Middle East Institute's Center for Turkish Studies Fazel Hawramy – Freelance journalist Lindsey Hilsum – International editor of Channel 4 NewsPresenter: Neal Razzell Producer: Beth Sagar-Fenton Researcher: Lizzy McNeill(Photo: Kurdish fighters withdraw from the border area near the northern Syrian town of Amuda on 27 October 2019. Credit: Delil Souleiman/Getty Images)

After deaths in the US and bans around the world, how risky are e-cigarettes? In some countries, smokeless cigarettes are all the rage. In the UK, doctors say if smokers switch from tobacco to e-cigarettes, it will save lives. But in the US, where the authorities are investigating an outbreak of lung injury linked to vaping, they’re advising vapers to consider stopping. In India, Mexico and dozens of other countries, vaping is banned altogether. It’s a confused international picture. Vaping is still relatively new and scientists are still researching how harmful it may be in the long-term. What we do know is that every year, eight million people die worldwide as a consequence of smoking tobacco. What are the potential health risks associated with vaping? We’ll find out from our expert witnesses, who include a neuroscientist, a pulmonary critical care doctor and a professor of nicotine and tobacco studies.(A young woman smoking an electronic cigarette at the vape shop. Credit: Getty images)