Is it norovirus or Shigella? How to tell the difference

If you’ve recently got the dreaded call home from daycare or school that your child is ill with a stomach flu, we see you. After having reached a 12-month high in February, it seems like cases of norovirus, a viral stomach infection, are still making the rounds. Add to that the fact that cases of Shigella bacterial infections are on the rise, and it’s a double whammy for parents.

A 2022 study published in the journal Pediatrics found that norovirus and Shigella are the leading causes of acute gastroenteritis outbreaks in school and child care settings. 

Norovirus and Shigella can spread rapidly, and to help slow the rate, some school districts are now urging families to keep sick kids home for an extra 48 hours—even after symptoms disappear, which means even more missed school or daycare days. 

Both illnesses cause similar symptoms: diarrhea, vomiting, low-grade fever, cramping and nausea—that we often lump under the catch-all terms of ‘stomach flu’ or ‘stomach bug.’ But how can you tell if you’re dealing with a virus or a bacterial infection? And when should you seek out antibiotics support… or not? Here, experts share a few ways to tell the difference between norovirus and Shigella.

Related: If your child has any of these 5 symptoms, you might want to keep them home from day care

Is it norovirus or Shigella? 

Shigellosis is an infection caused by the bacterium Shigella spp., whereas norovirus is caused by a group of single-stranded RNA viruses. 

Both infections are marked by symptoms ranging from nausea to cramping, diarrhea and vomiting. The best way to tell if you’re dealing with norovirus or Shigella is via stool sample, though doctors may usually be able to diagnose the infection based on symptoms, duration and whether your region is experiencing an outbreak in one over the other. 

Symptoms of norovirus in kids

Norovirus in kids usually shows up as vomiting, whereas adults may experience more diarrhea, notes Roger Seheult, MD, a quadruple board-certified doctor in internal medicine, pulmonary diseases, critical care medicine, and sleep medicine, and medical advisor for Intrivo. 

Here are the symptoms you might expect with norovirus: 

• Diarrhea
• Vomiting
• Nausea
• Stomach pain

Less commonly, norovirus may also present with: 

• Fever
• Headache
• Body aches

Symptoms of shigellosis in kids

Shigellosis in kids is typically marked by watery diarrhea. 

Other symptoms you might expect with shigellosis can include:

• Diarrhea that contains blood or mucus
• Belly cramps
• Fever
• Loss of appetite
• Nausea and vomiting
• Painful bowel movements
• Tenesmus, or the feeling of needing to poop even though your bowels are empty

Related: What to know about shigellosis in kids

Differences between norovirus and Shigella

When looking at symptoms, the primary differences between norovirus and Shigella are minor, but there are a couple notable differences:

• Shigella infection may be more likely to present with a fever
• Norovirus tends to start off with vomiting and then progresses to diarrhea, or both may start at once, Dr. Marci Drees, chief infection prevention officer with ChristianaCare, tells ABC6 News.
• Shigella infection tends to mainly show up as diarrhea rather than vomiting, Dr. Drees notes.
• Norovirus may last 1 to 3 days
• Shigellosis may last 5 to 7 days

Though Shigella may last considerably longer than norovirus, both can shed in the stool for days or even weeks after symptoms resolve. 

Treating norovirus vs. Shigella

Because norovirus is caused by a virus and not a bacterium, taking antibiotics won’t work. In most cases, antibiotics aren’t warranted for shigellosis, either, as the majority of cases are mild in kids, Ali Alhassani, MD, Head of Clinical at Summer Health, a pediatric telehealth platform, and a pediatrician at Boston Children’s Hospital, tells Motherly. Though antibiotics may shorten the duration of shigellosis by a couple days, given the rise in drug-resistant strains of Shigella, avoiding antibiotic use may be wisest, unless your doctor deems them necessary. 

Keeping kids hydrated, offering small amounts of bland foods and trying to promote lots of rest are the best treatment methods for either illness. A children’s electrolyte formula may be helpful to prevent dehydration, and if a fever arises, talk to your child’s doctor about whether fever reducers might help your child feel more comfortable. (In mild cases, it may be best to let the fever run its course without intervention.) Watch out for signs of dehydration in kids, especially if you suspect Shigella, as the infection could take longer to run its course. Again, reach out to your doctor for any concerns.

Preventing norovirus and Shigella

The Pediatrics study found that between 2009 and 2019, there were 4,633 outbreaks of norovirus and Shigella (though many go unreported, so the true number is likely higher). Norovirus accounted for about 51% of the outbreaks, while Shigella spp. caused about 16%. 

As for outbreak setting, the study found that about 65% of school outbreaks were viral, while 10% were bacterial. But in child care settings, about 37% were viral, and 41% were bacterial. 

“Outbreak prevention and control in these settings should focus on handwashing, cleaning and disinfection with effective products, and the exclusion of ill children and staff,” the study authors wrote. 

Related: 12 must-have products for baby during cold & flu season

At home, that looks like regularly bleaching common surfaces and bathroom fixtures, washing soiled laundry and linens in hot water and lots of handwashing to prevent the infections from spreading among family members. If you’re the one who’s sick, try to avoid preparing food for others. If that’s not possible, make sure you work up a good lather with lots of scrubbing.

“Even with good handwashing it takes scrubbing with soap and hot water for at least 30 seconds to be able to eliminate norovirus,” notes Dr. Seheult. (Admittedly, 30 seconds of handwashing is tough with most littles, but it’s worth it.) The CDC notes that hand sanitizer is not effective at preventing norovirus—and though it may work against Shigella, using soap and water for either illness is your best bet.