E. coli, listeria and salmonella bacteria have been making news, again, for sickening Americans. But what exactly are these tiny troublemakers?
Truthfully, unless you have a microscope and samples of bacterium (and an understanding of microbiology), it can be hard to tell the difference between them.
But health experts carefully track outbreaks of each to limit harm. In recent months, authorities say dozens of people have been sickened with E. coli from eating McDonald's Quarter Pounders, and one person has died; 59 people were hospitalized and 10 died in a listeria outbreak linked to sliced deli meat; and 93 people across about a dozen states were infected with salmonella from eggs.
It's important to note that while concerning, food recalls and safety alerts aren't uncommon. They can be viewed on the Food and Drug Administration's list.
Here's what to know about the bacteria behind these recent food recalls:
E. coli: There are different types of Escherichia coli, or E. coli, that exist in food and water, and in humans' and animals' intestines, the U.S. Centers for Disease Control and Prevention said. It's often transmitted through food or water contaminated by human or animal feces.
Certain types of E. coli can trigger different bodily responses. Some forms can make people sick. The Shiga toxin-producing infection is the most common E. coli illness.
Listeria: Listeria sickens people through food, and it's the third-leading cause of foodborne illness death in the U.S., according to CDC.
The bacterium is unique because it thrives in cool, damp environments, the U.S. Department of Agriculture said. Listeria can grow when refrigerated.
Salmonella: Salmonella causes the most common foodborne illness deaths.
Salmonella live in people and animals' guts. Fewer than 100 of more than the 2,500 Salmonella types of bacteria cause illness. Illness is triggered from eating contaminated food, drinking or having contact with water, or touching feces, animals or animals' habitats.
E. coli: Symptoms typically start three to four days after consuming contaminated food or water. The Shiga toxin-producing form of E. coli, the strain identified in the McDonald's outbreak, causes severe stomach cramps, diarrhea that's often bloody, and vomiting. People can develop serious kidney issues that require hospitalization.
Listeria: There are two types of illness, intestinal and invasive.
Intestinal illness is harder to diagnose because laboratories don't regularly test for listeria, CDC said. Symptoms - such as diarrhea and vomiting - usually start within a day of eating listeria-contaminated food and typically last up to three days.
Intestinal symptoms tend to be mild, but some develop the invasive form, which means it spread beyond their gut. Symptoms start around two weeks after eating food contaminated with listeria.
People who aren't pregnant can expect fever, muscle aches and fatigue that feel like the flu, headache, stiff neck, confusion, loss of balance and seizures. Around one-in-six people with invasive listeria illness die.
People who are pregnant can have fever and the flu-like symptoms of muscle aches and fatigue. Symptoms are typically mild, but an invasive illness during pregnancy usually causes miscarriage, stillbirth, premature delivery or a life-threatening infection to a newborn, CDC said.
Salmonella: Symptoms usually start between six hours and six days after consuming bacteria, CDC said. Most sick people have stomach cramps and watery diarrhea that might contain blood or mucus, and some can have headache, nausea, vomiting and loss of appetite. They usually recover without treatment after four to seven days.
However, some are more at risk of severe illness that requires medical treatment or hospitalization. This includes children younger than 5 years old, elderly people ages 65 years and older, and people with weakened immune systems.
Call a doctor if experiencing diarrhea or vomiting that lasts more than two days, bloody stool or urine, fever higher than 102 degrees, signs of dehydration, and long-term complications.
Consumers can take simple steps to reduce risk of illness. To start, check for food safety alerts and recalls.
Regular hand-washing, with warm soap and water, before and after preparing food, or after touching an animal or contaminated items such as diapers, is an easy way to reduce risk of illness, USDA said. Clean and sanitize items or surfaces that have come in contact with raw foods or waste. Also, don't cross-contaminate foods or surfaces.
Salmonella grows with warmer conditions, according to CDC. Refrigerate or freeze perishable foods, prepared foods and leftovers within two hours, or sooner if it's hot outside.
Listeria thrives in refrigerators, FDA said. Temperatures inside fridges should be 40 degrees or below, and freezers at 0 degrees. Also, make sure to use ready-to-eat refrigerated foods before the "Use By" date listed on packaging, because listeria has more chance to grow the longer it's stored in the fridge. Also, clean refrigerators regularly.