Listeria is believed to have left three people dead, putting the NHS on high alert, but its symptoms are not always obvious.

Three people are dead and two are injured after eating chocolate mousse thought to be contaminated by listeria bacteria (Picture: PA/Getty) Listeria is believed to have left three people dead ...

Listeria is a bacteria which can cause the infection listeriosis, according to the NHS. It is rare and in most cases can go away on its own, however, some can become seriously ill with the infection.

The patient count in an outbreak of infections from Listeria monocytogenes is increasing as the Food and Drug Administration continues to look for a ...