§ Mr. Hinchliffe
To ask the Secretary of State for Health what information he has on the number of listeria monocytogenes bacteria which need to be consumed to cause illness in vulnerable people.
§ Mr. Kenneth Clarke
According to a recent WHO working group, virtually nothing is known about the infectious dose of listeria monocytogenes in man. It is likely that the infectious dose may be related to host susceptibility. The detailed follow-up by the public health laboratory service of cases of listeriosis in the United Kingdom may shed some light on this.