Bio-terrorism could kill more people than a nuclear war, tech titan Bill Gates has warned.

In a chilling address to the Munich Security Conference, the board member of Microsoft said that advances in genetic engineering could allow elite terrorism groups to tailor biological viruses and convert them into weapons.

Gates believes that one of the most harmful viruses could be engineered in the common flu bug. Using a group of contagious strains, it would be easy to manipulate the virus to affect even the most widespread of populations.

"The next epidemic could originate on the computer screen of a terrorist intent on using genetic engineering to create a synthetic version of the smallpox virus… or a super contagious and deadly strain of the flu," said the billionaire.

Intelligence agencies in the UK and US believe that Islamic State (Isis) is trying to develop biological weapons, but in spite of this, Gates believes that governments are still complacent about the risk.

"Natural epidemics can be extremely large. Intentionally caused epidemics, bioterrorism, would be the largest of all," said Gates to The Telegraph.

"With nuclear weapons, you'd think you would probably stop after killing 100 million. Smallpox won't stop. Because the population is naïve, and there are no real preparations. That, if it got out and spread, would be a larger number."

Gates added that it was essential to prepare for the threat with military precision.

With the development of new vaccines and drugs, these medical developments could stop the attacks from spiralling out of control.

"This includes germ games and other preparedness exercises so we can better understand how diseases will spread, how people will respond in a panic and how to deal with things like overloaded highways and communications systems."

In an IPSOS Mori poll led by the Bill and Melissa Gates Foundation, 83% of Britons aged between 16 and 75 said that violent terrorist attacks concerned them the most about global anxieties, with 71% concerned about infectious diseases than warfare.