According to the U.S. Centers for Disease Control, more than 100,000 Americans get sick from salmonella in eggs every year. Salmonella is a bacteria that can grow on the shell of an egg as well as inside it, which is why health officials advise consumers to wash and cook eggs thoroughly.

Symptoms of salmonella infection include fever, diarrhea, nausea and vomiting. But for elderly people, children and those with compromised immune systems, it can pose more serious health problems and lead to death. So far, there are no reports of any illnesses in Maine. But Caroline Smith DeWaal says this latest outbreak has the potential to grow.

“There have already been nearly 300 reported cases of illness, and the quantity of eggs being recalled goes back three months, which means that a lot of eggs may still be in consumers’ refrigerators,” says DeWaal, the director of food safety for the Center for Science in the Public Interest, which represents more than 900,000 consumers in the U.S. and beyond.

Last week, Wright County Egg of Galt, Iowa voluntarily recalled 13 brands of its eggs, including those sold under the Farm Fresh, Shoreland, Albertson, Mountain Dairy and Dutch Farms brands. Wright County Egg, which is operated by DeCoster Farms, is now undergoing an FDA review of its records and testing for salmonella.

“The DeCoster Egg Farms have a long history of worker violations, environmental violations and extreme animal cruelty, so unfortunately it’s no surprise that this has a connection to one of the largest egg recalls in history,” says Nathan Runkle, the executive director of the Ohio-based animal rights group, Mercy for Animals.

In 2009, the group sent an undercover worker to DeCoster Egg Farm in Turner, Maine, where he documented the mistreatment of hens. The case resulted in a $125,000 fine and a pledge to make improvements, including more testing for illness, regular visits from a veterinarian and worker training.

In Iowa, Wright County Egg houses more than 7.5 million hens. And Runkle says the outbreak shows why small wire cages that house four or five hens apiece should be outlawed. “When we cram birds in cages on factory farms, where they can’t spread their wings, and these birds are living in filth, the risk of salmonella being spread onto consumers is increased dramatically.”