One of the most fatal Listeria outbreaks in US history was traced to a cantaloupe packing shed in Colorado.

Unhygienic conditions at the shed are said to have promoted the growth of Listeria that got into the shed by unknown carriers.

The outbreak is said to have killed at least 25 people and caused severe symptoms in 123 others. It has also resulted in a miscarriage and has spread over 26 states.

The US Food and Drug Administration (FDA) say that water had collected in the plant, which made it difficult to clean and sanitize the plant.

The packing shed is a part of Jensen Farms. The outbreak is the most fatal one since 1985, when badly pasteurized Mexican–style soft cheese infected 148 people and killed 48. The contaminant could have come from trucks carrying the melon, or from the fields where the fruit is grown.

Listeria is widely present in agricultural environments. They can be found anywhere including decaying vegetation and even in fields where food is grown. But the amounts found in these places are too little to cause any health hazards. Listeria monocytogenes is a common cause of US food recalls mostly in processed meats and cheeses. The fact that Listeria was found in fresh produce is something to be worried about.

People whose immune systems are weak tend to be at a greater risk than anyone else. Elderly people and pregnant women also risk getting ill. Most of the people who died after being infected by Listeria were the elderly.

The symptoms are fever and muscle aches usually come after severe bouts of diarrhea and other gastric problems.

The FDA says that the conditions at the Jensen Farms are not representative of packing farms in the country. Both say that the plant would not be distributing any more food till the agency said it was safe to do so.