Media playback is unsupported on your device Media caption Hannah Fry needs your smartphone and your help to run the project

We seem to be suffering from a global amnesia. Ask any passerby - as we did - “What was the most catastrophic cause of death in the last 100 years?” and you receive the usual suspects: WWII, perhaps WWI. There are also some less obvious replies: Chernobyl, the Boxing Day Tsunami, Hiroshima. Very, very rarely will anyone say Spanish Flu, and yet that particular pandemic killed up to 100 million people.

There have been three others since then. Even more astonishing is that the UK Government considers another flu pandemic so dangerous to our society that it tops the list of the newly updated National Risk Register for Civil Emergencies.

So it’s particularly timely that the BBC has just launched the BBC Pandemic App on the iOS App Store and Google Play.

This free app is part of the biggest experiment of its kind, a citizen science experiment that aims to spread a virtual pandemic - an outbreak of a simulated infectious disease around the entire country.

That may sound like an odd thing to want to do but, if successful, the BBC Pandemic could help save lives when – not if – the next lethal pandemic spreads across the world.

With international air travel at over four billion flights last year alone, stopping a flu pandemic taking hold is pretty much impossible nowadays, but the BBC Pandemic App will help a team of mathematical epidemiologists from the University of Cambridge and the London School of Hygiene and Tropical Medicine predict how a virus could spread across the UK and, crucially, test what might be done to slow it down.

Media playback is unsupported on your device Media caption Who knew flu could be such a big killer?

The problem with pandemic flu viruses is that they emerge unannounced, unlike the seasonal flu we experience every winter.

Seasonal flu can be deadly too and the warning signs from Australia show that this year could be a bad one, but at least we get a heads-up from our southern neighbours several months in advance.

This gives the critical time necessary to get a vaccine tailor-made and manufactured in sufficient volume to vaccinate key workers and those most vulnerable.

But, every now and again, the animal world creates a strain of the flu virus that humans have never seen before - we have little protection from our immune system, or enough time to make a vaccine before the virus has started to spread.

The 2009 pandemic was commonly known as swine flu because the human virus contained genes from a pig flu virus. The devastating Spanish Flu pandemic was caused by a virus that seems to have emerged from birds.

Planning for another pandemic is the best defence we have until vaccine technology manages to catch up. And that’s where everyone in the UK can help, by downloading the BBC Pandemic App.

Once downloaded, users will be asked basic questions like age and employment status.

Then the app will track users’ approximate position every hour for just 24 hours - but the GPS will only be within the nearest square kilometre. Privacy as well as data protection is taken very seriously by the team.

At the end of the 24 hours, there are a few questions about the kind of face-to-face contacts the users made in that time.

And that’s it. Simple but enough to provide real data the researchers can use to help predict the spread of a real outbreak.

The challenge is they would like 10,000 UK-wide to download the app and join in.

This has never been done before so anyone taking part will be participating in ground-breaking research.

The results will be shown in the BBC Pandemic documentary on BBC Four next year, presented by UCL mathematician Dr Hannah Fry and emergency medic Dr Javid Abdelmoneim.

To download the app go to the App Store or Google Play and search for “BBC Pandemic”.

There's much more information on the BBC Pandemic webpage. And, for those people who don't have a smartphone, there will shortly be a questionnaire on the webpage so that everyone can join in.