TCA, vol. 35: The Stomach Flu
Its not the flu, and it doesn't infect your stomach.
It’s something we all dread…. the “stomach flu”. A catch-all phrase that includes all of the viruses that cause gastroenteritis (gastro=stomach, enteric=intestines, itis=inflammation). The most common cause of gastroenteritis is the Norovirus. Also lovingly called “the winter vomiting disease” or “the cruise ship virus”. Let’s learn more about this gnarly bug which peaks in incidence between November and April.
The Numbers
The USA:
Causes 19-21 million infections per year (thats 1 out of every 15 people)
The most common cause of food-borne illness (58%)
Causes 2,270,000 outpatient visits, 465,000 ER visits and 109,000 hospitalizations yearly
Worldwide:
Causes 20% of all gastroenteritis
685 million cases per year
50,000 child deaths per year
$60 billion dollars in costs for healthcare and lost productivity
What’s in a name?
There are a lots of “names” for this type of gastroenteritis. Let’s pick them apart:
The Stomach Flu. I think this one bothers me the most because it confuses people into thinking that this disease is caused by Influenza. It is not. Influenza virus only infects the respiratory tract. The “flu” part of this name comes from the fact that some of the symptoms of gastroenteritis are what’s known as “flu-like symptoms”. During influenza infection, the virus stimulates the immune system to produce a massive amount of cytokines, or immune cell communication molecules. These molecules make your feel feverish, tired, and have muscle, joint and headaches. Many viruses cause these symptoms, but influenza seems to be really good at it, so this collection of symptoms is called “flu-like symptoms”. Even though Norovirus does not infect the stomach, vomiting is a major symptoms of this disease…. hence the “stomach” part of stomach flu. There are no known viruses that infect the stomach, they all infect the intestinal lining. Vomiting is initiated when the virus infects the intestine, which then signals to the brain via the vagus nerve that “something is amiss”. The brain’s area postrema, or “vomiting center” (real thing, y’all) makes you queasy and nauseated. The idea being that there may be some contaminated food still in the stomach, so let’s get that out. Diarrhea does the rest of the dirty work.
The Cruise Ship Virus. While Norovirus is not the only disease commonly transmitted on cruise ships, it is one of the most common. Norovirus easily transmits in crowded areas, among people who have questionable personal hygiene, and when there are a lot of commonly touched surfaces (which basically describes every cruise ship I’ve ever been on). But, this is also true of places like college dorms, day care centers, nursing homes and schools: other places where Norovirus commonly circulates. Interestingly, cruise ships are REQUIRED to report any outbreaks of gastroenteritis but other types of places are not. So, it very well may be that outbreaks are just more visible on cruise ships because of the tracking.
The Winter Vomiting Disease. It has been observed that Norovirus incidence peaks in America from November to April. There are a LOT of hypotheticals about why this is the case: The temperature or relative humidity allows the virus to stay intact outside the human body for longer making transmission more likely; people coming together in large gatherings for the holidays; human immunity waning in the winter months; vitamin D levels decreasing due to fewer hours of daylight exposure. Which one of these is the reason (maybe all of them to some degree) is not known.
Norwalk or Norovirus. This virus was orginally identified in Norwalk, Ohio in 1968 after an outbreak at Bronson Norwalk Elementary School. In the past it was very common to name viruses after a geographical landmark where they were first discovered. Ebola virus = Ebola river, Zaire (Now called DR of Congo). West Nile Virus = West Nile district of Uganda. Well, the good people of Norwalk, Ohio were not too pleased with having their town associated with a puking disease, and they made some noise about it. In response, officials started referring to it as “Norovirus”. Officially, the species name of this virus is Norwalk virus, but it belongs to the Norovirus genus. Around 2011, the ICTV (the international committe on taxonomy (naming) of viruses) received a request from one Japanese individual to change the name Norovirus to something else because it might bring shame to Japanese folx with the family name “Noro”. The ICTV recommended people call it the “Norwalk virus” instead. But I hear it both ways so I guess its a constant tug of war between pissed off Ohioans and pissed off Japanese.
Sidebar: Arguments about virus names are common. A type of Hantavirus that transmits by rodent pee and poo was discovered in the 1990s in a member of the Navajo nation. The virus was called Navajo virus, until the members of the Navajo nation raised objections. The virus was renamed “the Four Corners virus” after the four corners area (where the four square-shaped states meet). Of course, the people living there raised a fuss. I guess the scientists who named the virus got exasperated because they eventually settled on the name “Sin Nombre virus” which is Spanish for “no name”.
How is Norovirus spread?
Are you ready for this? Hold onto your butts….. the official name for this type of spread is “fecal-oral”. Which means the virus exits one person in their feces, and then is swallowed by the next person. I’ll give you a minute to recover.
In reality, this happens when poo particles (or to a lesser degree, vomit particles) contaminate food, water or surfaces. The most common ways this happens:
You eat food contaminated with virus. This could be because an infected person prepared the food having not washed their hands appropriately; raw fruits or veggies were grown in a field contaminated with human poo (This is a thing. Some farms don’t provide bathrooms for their workers so they just squat in the field); someone threw up near food and vomit spray contaminated it. Eating filter feeding shellfish raw (like oyesters) can also transmit Norovirus if they were grown in sewage contaminated waters.
You drink water contaminated with virus. This could be from sewage contamination of water; breakdown of water treatment during heavy storms/natural disasters/war/etc; swallowing lake or poorly chlorinated pool water.
You touch a surface contaminated with virus and then touch your mouth or your food without washing your hands first.
As you can imagine bathrooms can be ground zero for surface contamination if someone has vomiting or diarrhea. Similarly, under-chlorinated pools transmit virus when people who have diarrhea go swimming. And good hand washing technique after using the bathroom and before eating/preparing food is critical for preventing transmission.
Unfortunately, Norovirus can linger on surfaces for a long time and is resistant to some disinfectants. It is still active after 700 days in water samples, up to 50 days on stainless steel and PVC, and for a week on refrigerated fruits and vegetables.
For common cleaning, chlorine bleach solutions are effective. You should also wash any contaminated clothing and underwear with detergent in the hot water setting and dry the clothes on the highest heat setting.
Is it deadly?
Not for most. There are approximately 600-800 deaths from Norovirus each year in the USA, and this is predominantly in those under 5 years old, or over 65. The numbers are higher elsewhere in the world, especially in areas where clean water is not available for rehydration, medical access is poor, or dehydration/starvation is already prevalent.
Wash your damn hands.
During the COVID pandemic, we all got a lesson in how to wash our hands appropriately. As a reminder:
You should wash your hands with soap and water, vigorously scrubbing all surfaces of your hands (don’t forget in between fingers, fingertips and thumb, and under nails if you have long ones) for 20 seconds. Rinse hands completely and dry with a towel or air-dry. I really don’t like the blow dryers in bathrooms because they circulate poopy public bathroom air. They are basically warm germ blowers.
When you wash your hands is also important. Wash every time you touch something that might be poopy: after you go to the bathroom, or touching bathroom surfaces, changing a diaper. Wash after you touch common surfaces. Wash before you prepare or eat food. Wash after you care for someone who is sick.
Stay happy, healthy and informed,
Jessica at TCA
Lucero, Y. et al. Norovirus: Facts and Reflections from Past, Present, and Future. Viruses. 2021.
National Foundation For Infectious Diseases. What is Norovirus? 2023.
Science Daily. Mechansim Behind Virally-Caused Vomiting Identified. 2011.
CDC. Norovirus Burden and Trends.
CDC. Facts about Noroviruses on Cruise Ships
CDC. Norovirus Illness: Key facts. Handout.
Fecteau, M. The Virus Named after an Ohio City. Ideastream Public Media. 2018.