You're right, it's about risk.
Say there is a joint population of the UK + France of 120,000,000 people. In the last 17 years there have been ~50 cases.
2 times a week 100,000,000 people eat cheese (not just unpasteurised).
So, in 17 years, we have a cheese-eating situation of:
(17 x 52 x 2 x 100,000,000) / 17
That's a one in 10,400,000,000 of having a listeria infection.
Do you feel lucky punk - well do ya? If you are feeling that lucky can you give me 6 random numbers between 1 and 48?