Well, the medical term for a stomach bug is viral gastroenteritis, and it’s generally caused by viruses like norovirus, rotavirus, and adenovirus, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). (Even though some call it a stomach flu it’s completely unrelated to influenza, or the flu, which is a respiratory virus.)
The most common way to get viral gastroenteritis is by coming into direct contact with someone who’s sick or by touching surfaces that have been contaminated with the stool or vomit from someone who has the bug. You can also get viral gastroenteritis after eating food prepared or served by someone who has a virus.
So food poisoning can be caused by viruses like norovirus (or hepatitis A). However, food poisoning can also be caused by a lot of other germs including bacteria like salmonella, E.coli, or Listeria, or parasites like Giardia or Cryptosporidium, according to Dr. De Latour.
Telling the difference can be tricky because you might not realize you’d been in touch with someone who was sick, says Rabia De Latour, MD, a gastroenterologist at NYU Langone Health. Although food poisoning due to bacteria generally shows up within one to eight hours of eating, stomach bug symptoms won’t appear until 24 to 48 hours of being around the person you caught it from—and that person might not show symptoms yet either. “There’s this incubation period,” says Dr. De Latour. “They’re walking around and somewhat contagious.” (If you wake up with a stomachache, find out the 12 things you should do right away.)
Once symptoms do show up, a stomach bug and food poisoning can look almost identical: stomach pain, nausea, vomiting, and diarrhea. The symptoms can be mild or severe, depending on the germ and a person’s susceptibility to it. Some telltale signs that your symptoms are serious are a high fever or blood in the stool, says Neal Shipley, MD, medical director of Northwell Health-GoHealth Urgent Care. “Viral illnesses are less aggressive,” he says.
See a doctor if you have a high fever or bloody vomit or stool, or your symptoms don’t get better within two days. Signs of dehydration, like a dry mouth or throat, low urine output, or feeling dizzy when you stand, are also a reason to seek help.
If your symptoms aren’t serious, try retracing your steps to figure out if you ate anything that was left out too long or wasn’t fully cooked. If other people you shared a meal with also have the same stomach issues, there’s a good chance you all got food poisoning, says Dr. De Latour. (Learn some more signs of food poisoning everyone should know.)
How do you treat the stomach flu or food poisoning?
Viral gastroenteritis and food poisoning in general are treated the same way—drinking plenty of clear liquids and eventually reintroducing bland foods—but knowing the difference will help if you end up at the doctor’s office. Antibiotics (which only work against bacteria) won’t help your viral gastroenteritis symptoms at all, says Dr. Shipley. Instead, a doctor might prescribe medicine specifically designed for an upset stomach or recommend an OTC product.
Washing your hands more often will help ward off both the viruses that cause stomach bugs and other types of bacteria and viruses that cause food poisoning, says Dr. De Latour.
Other important ways to avoid food poisoning are to cook food thoroughly and to a high enough temperature; avoid unpasteurized products and raw milk; and practice good hygiene in the kitchen to avoid cross-contaminating food while cooking. (Don’t miss the meaning behind these other 7 stomach pains.)