BRITAIN is most at risk from another terrorist attack on public transport, but a flu pandemic would have an impact on far more people, a government analysis warned yesterday.
It published its previously secret "national risk register" which sets out the most significant threats to the country over the next five years.
A flu pandemic is deemed to be likely to impact on the greatest number of people, with half the population likely to become infected and leaving between 50,000 and 750,000 dead.
But attacks on public transport, at a time the UK's terror threat status is "severe", are judged more likely, in the wake of the 7 July attacks in London in 2005 and those in Moscow and Madrid in 2004.
This is due to the combination of the large number of passengers and the "open" nature of train and underground rail networks, contrasting with the high levels of security at airports.
The report states: "Of the different malicious attacks outlined in this document, conventional attacks on transport systems are judged to be some of the more likely to occur; although the likelihood of them affecting any one individual is still very low."
An attempt to cause chaos with a computer virus is regarded as the second most likely threat to the country.
The document compares 12 major risks in terms of their potential impact and likelihood of them happening. Attacks on crowded places and severe weather are also more likely than a flu pandemic, though experts believe there is a "high probability" of this occurring.
A flu pandemic would have the widest impact on the public – there were three in the 20th century, with 228,000 Britons dying from an outbreak of "Spanish flu" in 1918 to 1919 – followed by coastal flooding and major industrial accidents.
While the government holds sufficient quantities of the Tamiflu vaccine to treat one-quarter of the population, the concern is that a new flu strain could spread rapidly at a time it would take four to six months to develop new vaccines.
Other concerns include major transport accidents, such as the Kegworth plane crash in 1989 in which 47 passengers died, animal disease, such as foot-and-mouth outbreaks and inland flooding.
The government's aim in publishing the report is to increase public awareness of the threats the country faces and to encourage public bodies, businesses and individuals to prepare for worst-case scenarios.
The security minister, Lord West of Spithead, rejected suggestions that publication of the register would simply cause unnecessary alarm.
"I have great faith in the public and they would prefer to have information because the thing that causes fear is ignorance of things," he said.