You can take precautions, but, unfortunately, there are few ways to fully defend yourself against gastrointestinal illness outbreaks. (HealthGrove photo via Mic445 / Flickr)

With all the news of foodborne illness outbreaks, names like norovirus and E. coli are in the forefront of Americans’ minds. However, many other bugs can cause equally unpleasant — if not worse — gastrointestinal symptoms.

The stomach flu, also known as gastroenteritis, can sneak its way into your system through the food you eat or person-to-person contact. Although the list of stomach-flu-causing bugs is long and varied, Summerland-based HealthGrove found 16 repeat offenders.

HealthGrove used data from the Centers for Disease Control and Prevention to curate this list of the 16 most common stomach bugs. These bugs have caused the highest number of outbreaks in the United States between 2009-2013. An outbreak is defined as an increase in the number of cases of a disease, above what is normally expected in the population of a region.

Although there is no way to defend yourself fully against these illnesses, simple precautions such as washing your hands and handling food carefully can decrease the risk.

#16. Enterotoxigenic E. coli


Outbreaks From 2009-2013: 1

This strain of E. coli is one of the biggest causes of traveler’s diarrhea and a major contributor to diarrheal disease in underdeveloped regions. This bacteria lives in the intestines of humans and animals and is transmitted via contaminated food or water.

Most people recover from infection within 48 hours and don’t require any specific treatment.

However, this strain is less common than many other forms of E. coli, such as Shiga toxin-producing E. coli (STEC), which causes far more outbreaks.

Note: This strain of E. coli has only caused one outbreak between 2009 and 2013, but the visualization counts outbreaks caused by all strains.

#15. Cyclospora


Outbreaks From 2009-2013: 1

The microscopic parasite cyclospora causes cyclosporiasis, an intestinal illness. People usually contract cyclosporiasis by consuming food or water contaminated with the bug. Those with healthy immune systems usually recover without treatment.

Untreated symptoms can last anywhere from a few days to a month or longer, however.

Typical treatments include antibiotics such as Bactrim and Septra.

#14. Astrovirus


Outbreaks From 2009-2013: 1

Astrovirus affects the gastrointestinal system and causes diarrhea and vomiting. These symptoms can cause dehydration, so it is important to drink fluids if infected with this virus.

Symptoms last between three to four days and typically resolve without medical intervention.

#13. Listeria


Outbreaks From 2009-2013: 2

According to the CDC, listeriosis typically affects older adults, pregnant women, newborns and those with weakened immune systems.

This disease is usually caused by consuming food infected with the listeria bacteria. Symptoms include fever, muscle aches and diarrhea.

This disease is particularly dangerous for pregnant women, as it can cause miscarriage, stillbirth or death of the newborn.

#12. Yersinia


Outbreaks From 2009-2013: 2

Most cases of yersiniosis are caused by the Y. enterocolitica species of the Yersinia bacteria.

Although Yersinia typically affects young children, anyone can get infected. Infection can cause symptoms including fever, abdominal pain and diarrhea. Symptoms usually occur four to seven days after exposure and can last one to three weeks.

#11. Staphylococcus aureus


Outbreaks From 2009-2013: 2

This bacteria is most commonly known for causing staph infections in hospitals, but it can also cause food poisoning if food is not handled properly. If food is contaminated and not properly refrigerated, the bacteria can multiply quickly and produce a toxin that causes illness.

Symptoms include nausea, vomiting, diarrhea and mild fever.

The illness is typically short-lived, however, as most people improve within 24 and 48 hours.

#10. Sapovirus


Outbreaks From 2009-2013: 12

Sapovirus is unknown to many clinicians, but it is responsible for many cases of viral gastroenteritis in the United States.

This pathogen was discovered in 1977 and is in the same family as norovirus. It is named after Sapporo, Japan, where the virus was first discovered after an outbreak in an orphanage.

Symptoms of infection include diarrhea, vomiting and fever and typically resolve within 48 hours.

#9. Clostridium


Outbreaks From 2009-2013: 19

Clostridium difficile, also known as C. diff., lives in the intestines of many people and is part of the normal balance of bacteria in a person’s gut. Though it typically does not cause problems, if the balance of microbes in your intestines gets thrown off, C. diff can grow out of control and start to release toxins that attack the intestinal lining.

Common symptoms include diarrhea and abdominal pain.

If clostridium developed while taking antibiotics, treatment typically includes halting the antibiotic regimen. If not, antibiotics may be prescribed. However, antibiotics may be prescribed sparingly as antibiotic-resistant Clostridium difficile is already a threat in many hospitals.

#8. Rotavirus


Outbreaks From 2009-2013: 19

This virus is most common in infants and young children, though older adults are not immune.

Symptoms include diarrhea, vomiting and fever, which can last three to eight days. While no antiviral drug exists to treat rotavirus, there is a vaccine for infants.

When dealing with rotavirus symptoms, drinking plenty of fluids helps prevent dehydration.

#7. Cryptosporidium


Outbreaks From 2009-2013: 36

This microscopic parasite causes the diarrheal disease cryptosporidiosis. Most commonly spread through drinking and recreational water, this parasite can survive outside the body for long periods of time due to its protective outer shell.

Symptoms of cryptosporidiosis generally occur two to 10 days after infection and the most common symptom is watery diarrhea. Other symptoms include vomiting and fever and can last anywhere between one to two weeks.

#6. Giardia


Outbreaks From 2009-2013: 48

The diarrheal illness giardia is caused by a parasite of the same name. It is found in soil, food and water that has been contaminated with the fecal matter of infected humans or animals, however it is most commonly transmitted through drinking water. Symptoms include diarrhea, gas, vomiting and dehydration and can last from one to two weeks.

Treatments typically include medications such as metronidazole, tinidazole and nitazoxadine.

#5. Campylobacter


Outbreaks From 2009-2013: 60

The Campylobacter bacteria is one of the most common causes of diarrheal illness in the United States. Typically, this bacteria is not related to concentrated outbreaks as it most commonly affects those who handle raw poultry incorrectly, such as not cooking it thoroughly and forgetting to wash food preparation surfaces.

The CDC reports that approximately 14 out of every 100,000 people contract the illness per year. Most infected people recover on their own within two to five days — antibiotics are only prescribed in the most severe cases.

#4. Shiga toxin-producing E. coli


Outbreaks From 2009-2013: 125

Also known as STEC, Shiga toxin-producing E.coli normally lives in the intestines of humans and animals. Though many strains of E. coli naturally live in human intestines and are actually harmless, STEC is one of the most commonly heard about with respect to foodborne outbreaks.

STEC typically causes diarrhea, vomiting and severe stomach cramps. Most people get better within five to seven days.

#3. Salmonella


Outbreaks From 2009-2013: 251

Salmonella infections are more common in the summer and are typically caused by two strains, salmonella typhimurium and salmonella enteritidis. When infected with salmonella, most people develop diarrhea, fever and abdominal cramps within 12 to 72 hours.

Those with impaired immune systems and the elderly or infants are more likely to experience severe reactions to this bacteria.

#2. Shigella


Outbreaks From 2009-2013: 301

In humans, the group of bacteria shigella causes shigellosis, which causes diarrhea, fever and stomach cramps about a day or two after exposure.

Usually shigellosis clears up in five to seven days. Frequent hand-washing can help prevent the spread of this bug.

#1. Norovirus


Outbreaks From 2009-2013: 3,215

Also known as the winter vomiting bug, norovirus incidence peaks in the winter. A December 2015 outbreak of norovirus sickened hundreds of people in Santa Barbara County.

Diarrhea, throwing up and nausea usually develop within a day or two after exposure. Given these symptoms, victims of this virus should remember to drink plenty of liquids to prevent dehydration. Most people recover within one to three days.

Although this illness is relatively short lived, the number of outbreaks far outnumbers those of other bugs on this list.

Comparing the Stomach Bugs


Click here for more research on other conditions on HealthGrove.

— Sabrina Perry is an associate editor at Graphiq, a Summerland data analysis and visualization startup. This article is based on data curated by HealthGrove, a division of Graphiq.