After analyzing four of the five types of Listeria implicated in last year’s deadly cantaloupe outbreak, scientists have discovered that a new outbreak strain was among those that contributed to the nearly 150 illnesses and 33 deaths caused by contaminated melons.
The researchers, an international team of government and university scientists, also compared the strains involved in the 2011 outbreak to those that had caused other outbreaks or been collected from other food facilities. By doing this, they identified two new sets of “epidemic clones” – strains isolated in different times and places that appear to have common ancestors.
Only five epidemic clones, or ECs, of Listeria had been identified prior to this study, which raises that number to seven.
FoodWorld 
Which strain of Listeria is linked with contaminated melons? Amel
It was Listeria monocytogenes and there were five strains implicated. There is more detail in the Link on the blog page.