Tests have been carried out throughout the week at the Pirbright research complex in Surrey, which is thought to be the source of the leak, after a virus being used in experiments there was identified as being the same virus to infect local cattle.

A report by the Health and Safety Executive concluded that release by human movement "must be considered a real possibility", but left open the question of whether it was accidental or deliberate. However, Dr Andrew King, the former head of molecular biology at the Institute for Animal Health in Pirbright, who is assisting the internal investigation, told The Daily Telegraph yesterday that there was "no way" the virus could have leaked by accident.

He said the centre is very "tightly run", contrary to some recent allegations.

"The idea that someone can work with a virus and get it on their clothes and walk out the door with it is laughable," he added.

"In my view it is impossible for the virus to escape." 

Source: Daily Telegraph