The Health Protection Agency has blamed the "ready-to-eat" salads from two leading supermarket chains for food poisoning in more than 300 shoppers.
Cryptosporidium parasite causes the disease cryptosporidiosis with diarrhea as the major symptom. According to HPA, the source could be tracked to bagged salads.
A survey on 25% of the affected people revealed that 46% of them remembered buying mixed leaf bagged salad from the Morrisons, while 11% ate spinach from the Asda chain.
The agency states that the data is statistically significant and the spinach, which is found in both the products, could be the source of the parasite.
However, both Morrisons and ASDS have denied the claim as the findings were based on statistics and not on testing.