There have been three major ice-cream recalls for listeria contamination in recent months, starting with Snoqualmie Ice Cream, in Washington state.

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WASHINGTON — With another recall of ice cream announced over fears of listeria contamination — the third in four months — consumers are wondering whether it’s safe to indulge in their favorite summer treat.

What to know about ice cream and listeria:

Q. What brands have been recalled?

A. There have been three major ice-cream recalls for listeria contamination in recent months, starting with Snoqualmie Ice Cream, a Washington state company that issued a voluntary recall in December for all its products produced from Jan. 1, 2014, until Dec. 21, 2014. At least two illnesses have been linked to Snoqualmie’s recalled products. On Monday, Blue Bell Creameries recalled all of its products on the market, which include ice cream, frozen yogurt, sherbet and frozen snacks. At least 10 people have been sickened by Blue Bell products contaminated with listeria in Arizona, Kansas, Oklahoma and Texas. Three people died in Kansas.

Jeni’s Splendid Ice Creams on Thursday announced a voluntary recall of all ice creams, frozen yogurts, sorbets and ice-cream sandwiches.

Q. What is listeria and why is it dangerous?

A. Listeria monocytogenes is a germ that can contaminate food and cause a deadly infection, listeriosis, that’s characterized by high fever, severe headache, stiffness, nausea, abdominal pain and diarrhea. Babies, seniors and people with weakened immune systems are particularly susceptible. Listeriosis has been known to cause miscarriage or stillbirth, a particular concern for expectant mothers craving ice cream.

“We see listeria associated with lots of other foods out there, and now we’ve added ice cream to the list,” said Doug Powell, a former professor of food safety in Canada and the U.S. who publishes barfblog, a food-safety blog.

The bacteria is found in soil and water, and it can be tracked into a manufacturing facility, carried by animals or spread by employees not using proper sanitation practices.

Q. Can listeria be killed?

A. Listeria can be killed with heat, but not cold. “Listeria grows slowly at refrigeration temperatures and it persists in frozen foods,” said Benjamin Chapman, a food-safety specialist at North Carolina State University.

Q. How did it get into the ice cream?

A. No one knows for sure. The companies and federal food-safety experts are investigating. Ice cream typically is pasteurized. That means the milk used to make it is heat-treated to kill pathogens such as listeria before it’s frozen. But there are other ingredients that go into ice cream that could be a source of listeria, such as flavorings. At least one Blue Bell product that tested positive for listeria contained cookie dough.

Jeni’s ice cream hasn’t been linked to any illnesses, but the company recalled its products after Nebraska health officials found listeria in a sample of ice cream. On Friday, Jeni’s said early testing suggested listeria was present in other pints from the same batch the Nebraska officials tested. The company said additional tests appeared to show listeria was present in Jeni’s manufacturing plant in Columbus, Ohio.

Q. Is it safe to eat ice cream?

A. Food-safety experts Powell and Chapman said yes.