Is it a cold, the flu or a stomach bug?

This is a post I’ve been meaning to do for a long while – and with cold season approaching and some time on my hands to get it done, here it finally is.

I commonly hear people refer to a stomach bug (more formally known as gastroenteritis) as the “stomach flu“. Hell, before I went through nursing school I’m pretty sure I used to call it that! However, this language can be confusing. Suddenly people are telling you they just have the flu, when they actually have gastro. Or, they have cold symptoms and interpret it as the flu because the two can be similar in many ways and easy to mistake for one another.

So lets break down these 3 cold season bad boys and see what they are and how to identify them; as well as how to deal with them (aka – for which ones should you attend the doctor and when?).

Disclaimer: this is not medical advice nor should it be interpreted as such. This blog is for informational purposes only. Please consult your healthcare provider for medical advice. Please also note Amazon affiliate links are used in this post and I may earn some small amounts from your purchases.

Gastroenteritis (Commonly Known As: a “stomach bug” or the “stomach flu”)

Let me start off by saying, gastroenteritis is unpleasant. I actually developed a legitimate fear of vomiting (known as emetephobia) because of having gastro in childhood. It took many years to get over it, and to be honest it still haunts me slightly to this day – though I will say the nausea and dry heaving of pregnancy helped clear it up a lot. And perhaps hangovers in my younger youth.

If we break down the word gastroenteritis, we find “inflammation (itis) of the stomach (gastro) + small intestine (enter)”.

What causes gastroenteritis?

Gastroenteritis can be caused by different things – which I think makes it confusing for people. It’s nice to be able to point at one virus or cause and say that is what it is! However, with many illnesses or syndromes, there can be the same set of symptoms caused by slightly different things.

Gastroenteritis doesn’t need to be caused by a virus, it can be caused by other things like bacteria or parasites. It can even be caused by a protozoan infection like Giardia, which you may have heard of if you have pets. There is also forms of non-infectious gastroenteritis – meaning it is not caused by an infection of any type, but sometimes by ingestion of harsh chemicals or certain drugs.

Common causes you may have heard of are food poisoning (from bacteria like Salmonella and E. coli) and norovirus, which is highly contagious. Rotavirus used to be a top contender too in North America, but the vaccination has severely reduced the rate of infection in children. Yay!

Viral gastroenteritis is usually the one that is called a “stomach bug”. It is spread through person-to-person close contact, or if you come into contact with a sick persons vomit or feces – or a surface where these things might have been/where viral particles may have spread to through contact (then you touch your face, eyes, mouth, etc – this is called contact transmission or fomite transmission).

It can also be passed on through airborne transmission after someone vomits (or otherwise spreads these now aerosolized particles)- the particles essentially stay in the air for a long period of time and often cover a significant distance.

You can read more about the Rotavirus vaccination in this post.

What are the symptoms?

Stomach symptoms of course – which can and often is both diarrhea and vomiting (but may only be one). Lovely. It really is so lovely. I have vivid memories of getting norovirus in my final semester of nursing school from our niece and nephew. They got it the night before we started having symptoms. Both my husband and I ended up rushing home from work to get to the toilet first. And we lived in a 1-bathroom apartment.

Abdominal pain may occur as well as intestinal or stomach cramps. You probably will not have an appetite understandably and because you’re losing fluids, there is a risk for dehydration. If the cause is viral, you may also have some typical virus symptoms like a fever, aches and pains, chills, and so on. This is why viral gastroenteritis can be mistaken for the flu, but we’ll get to the differences in a moment.

Treatment or Management

Sickness can last a few days or a week in children. The main concern and priority here is managing the risk for dehydration and electrolyte imbalance. Fluids are key – options like Pedialyte are especially great in these situations, to maintain those lytes. If your child won’t drink it, there are also freezie options. You can also talk to your pharmacist about options available locally to you.

If your child is showing early signs of dehydration – nausea, dizziness, dark yellow pee or decreased # of wet diapers, dry lips/tongue – then they need to be seen. Contact your doctor and also your pharmacist as above for recommendations.

If they are showing any severe signs – like loss of consciousness or change of level of consciousness (they seem confused or drowsy), increased breathing rate or heart rate, they are lethargic, pale or very cold – you will want to take them in immediately to emerge (you can still call your GP but don’t wait).

Outside of dehydration – gastro is generally a “deal with at home” situation, unless you have a bacterial or other form that requires medication. Generally, the symptoms would last longer than a few days (bacterial infections often cause bloody diarrhea too) if this is the case. It can be hard to know – so feel free to contact your doctor’s office by phone for triage. Avoid attending the office unless advised by your physician because of how contagious the viral causes can be to others – call first.

Fluids + rest should mend most people up in a few days. If you or your child have other symptoms – like a fever – you can treat those as advised by your medical team. Notably in children, fluids should not be consumed all at once as this may cause more vomiting – if you’re dealing with vomiting for the first time in your child, you should contact your doctor and medical team for further guidance.

The Common Cold

Ah, a cold. It is unpleasant too, in its own way. More often than anything – it is confused for the flu. Lets talk about colds first, then we can compare the two at the end to see what major differences stand out.

The common cold, as it is often called, is also known as an upper respiratory infection. Did you know there is an upper and a lower respiratory tract? No, I am not saying that sarcastically – it may not be common knowledge that your nasal passages and throat are considered the upper portion of your respiratory system; the lower portion would then of course be the lungs and their connections.

What causes the common cold?

It is common because it is caused by so many viruses! That is also why you can have multiple colds in a row.

Since we’re living in a pandemic (yes, still present tense), I am sure many now understand how viruses are spread based on the protective measures that were in place. ICYMI, colds are spread by respiratory droplets – when you sneeze or cough and particles fly into the air. Respiratory droplets are heavier than aerosols (like with gastro) so they fall to the ground (or nearby surfaces) almost immediately. It is important to note that not all respiratory viruses create large droplets – some (like COVID) may create aerosols. Others come into contact with these and can pick it up themselves. That is the simplified version of course, and also why wearing masks (and social distancing, and staying home when you’re sick, etc.) reduced flu rates and colds!

Special mention of what does not cause a cold:

  • Going outside in the rain or cold without a jacket
  • What you eat or your diet

Thank you for coming to my TED talk.

Pause – I’ve now mentioned three types of viral transmission. Airborne (gastroenteritis) and respiratory (most viral colds). Also contact transmission which can occur in both scenarios. The main difference between airborne and respiratory spread is that respiratory droplets don’t tend to 1) be suspended as long in the air because they are heavy; and 2) therefore also don’t travel as far of a distance. This image from the WHO gives a great explanation and comparison. Viruses spread via aerosolized droplets are therefore highly contagious.

What are the symptoms?

You guys know these. Stuffy nose, scratchy or sore throat, sneezing, coughing and just feeling unwell or rundown. Again – we will look at the differences from the flu in a moment.

Treatment or Management

A cold can be managed at home, like most cases of gastro. Unless it is prolonged or you’re having trouble breathing, you usually should be ok to self medicate + manage as you see fit and following any guidance from your provider keeping in mind your unique health situation. If you’re concerned but not sure if you need to be seen, you can call your physician/NP office or a service like Telehealth to get triaged.

Rest and fluids. Medications dependent on symptoms – for example, you may want to use Tylenol or Ibuprofen for a fever or aches/pains. Consult your doctor or pharmacist for dosages for children and follow the instructions. Other options can include cough medicines bought over the counter, humidifiers, saline nasal sprays, and more. Each persons way of coping with a cold will be slightly different.

Check out my posts on use of ibuprofen and acetaminophen with children!


Last but not least: the flu, which is more formally known as influenza. Again – lets break it down and then we can compare the 3.

What causes the flu?

Influenza is caused by a virus… influenza. There are different types though – A, B, C and D are currently recognized. A and B are the ones connected with “flu season”, but most predominantly A.

There are also different strains of each type – so influenza A from last year may not be the same as the one this year. This is also why the flu shot is an annual vaccination – it is tailored to each years predicted dominant strains. And yes, this is why some years it doesn’t seem as effective – because it is a prediction (but they often get at least one of the strains right). You can read more about how they select the virus each year for the flu vaccine here (US) or here (Canada), or on the World Health Organization (WHO) website.

Just like both viral gastroenteritis and the common cold (caused by a virus), the flu can spread through contact transmission – though this is less common than via respiratory transmission. Can influenza be airborne? It is actually being debated, especially since the pandemic. A 2018 study did find aerosolized influenza particles from exhaled breath, for example. However, it is definitely still mostly spread through respiratory droplet transmission.

Influenza can affect the lower respiratory tract (in addition to the upper tract and the rest of your body), which is why you will see some differences in symptoms from the common cold.

What are the symptoms?

Common symptoms include feeling unwell (aches, pain); experiencing chills and/or a fever;; and often a cough. You may also experience headaches, fatigue, and cold symptoms like stuffed/runny nose and/or sore throat. Children may present with slightly different symptoms, like diarrhea (which is otherwise unlikely to see in adults with influenza) and nausea and/or vomiting.

Treatment or Management

Like both the cold and gastro, many cases of the flu don’t require a doctors visit. However, you should monitor your (or your childs) symptoms carefully. With children, we are concerned about dehydration (if they are taking in less fluids, but also if they have vomiting or diarrhea) and change in consciousness or severe irritability. You’d also be concerned, for both adults and children, if there is any difficulty breathing; or really any symptoms that you feel concerned about. If it is mild, you can call your provider’s office or again, a service like Telehealth for guidance. If you are concerned about yours or your child’s wellbeing, breathing, consciousness or a risk for dehydration, an ER visit would probably be more appropriate. Talk to your provider’s office or Telehealth for guidance – but I also say that we know ourselves and our children best, so also trust your gut. Pneumonia and other complications can develop from influenza – especially if you are in a high risk population (seniors, chronic diseases, young children).

If influenza is mild for you, you can stay home and rest, take in adequate fluids, and use medications as is appropriate/safe for you. Again – your provider + a pharmacist are resources that you have available to you. If you’re considering over the counter (OTC) medications, you can always talk to your local pharmacist for guidance. Some cold/flu medications are not appropriate for young children. This should be noted on the boxes, but please use the system and ask your pharamcist too. They are literally the experts.

There is no vaccination to prevent gastroenteritis (other than caused by rotavirus, which I mentioned above) or the common cold, but there is an annual influenza vaccination available to you and your family. I’ve discussed the flu vaccine in detail here for pregnant women and I also have a series on flu vaccine myths here. I will likely do an updated post on this coming into flu season now, so stay tuned. In the mean time – discuss with your provider if the flu shot is right for you and your family.

Did your child just get a vaccination? Here are some after care tips!

Summary and Comparison

Here is a short little summary of the 3 things we discussed in this post.

In words, colds tend to be mild for most people – with typical “cold symptoms”, like sore throat, runny nose and sometimes a cough. You should be able to deal with a cold at home, unless complications develop (not usually the case). Use your resources (provider, telehealth, pharmacist) where possible if you have concerns.

Influenza tends to be more “widespread” than a cold. Symptoms affect your whole body, and a fever is common. Complications can occur – again, resources are here to help. You can often manage this one at home too – but sometimes you may need more support. Children may present with symptoms that are similar to gastroenteritis, but they will likely have additional symptoms too like a cough.

Gastroenteritis is a “stomach bug”, or it may be caused by something else like food poisoning/bacteria. Main symptoms should be related to the gastrointestinal tract, like vomiting or diarrhea. You may also feel overall unwell because well – these things take a lot out of our body. Sometimes there is a fever but there will not be a cough or cold-like symptoms with this one. Again – mostly treatable at home unless it is lasting a long amount of time or you have dehydration concerns (especially in children). Resources, resources, resources.

When possible – avoid going into a doctor’s office, call first to prevent the spread of any of these illnesses. As you can see, gastro and influenza can be very contagious in particular. If you need to go in, consider wearing a mask and social distancing where possible. You should also avoid going anywhere in public while sick – just like is advised with COVID-19. That is why calling your office or Telehealth and similar services are great resources. If your doctor offers virtual appointments, this may be a good option (but with limitations because a doctor cannot examine your throat, for example, via virtual visit).

Hand hygiene is an absolute must with all three but it would be great if you’re just practicing hand hygiene daily regardless of your health status.

Remember that all of these are viral illnesses and none require antibiotics.

I wish you all good health through the fall and winter months this year! I hope to write up some care guides for children for these illnesses in the near future! Stay tuned.

Additional Resources

Overview of Gastroenteritis – MSD Manual

Gastroenteritis – Canadian Society of Intestinal Research

Dehydration in Children– The Royal Children’s Hospital Melbourne

CDC Cold VS Flu

CDC Key Facts About Influenza (Flu)

CDC Selecting Viruses for the Seasonal Influenza Vaccine

Government of Canada – How Canada influences the development of the annual flu shot

World Health Organization (WHO) – Global Influenza Programme

Studies For Further Reading:

Airborne transmission of respiratory viruses (Wang et al., 2021)

Infectious virus in exhaled breath of symptomatic seasonal influenza cases from a college community (Yan et al., 2018)


One response to “Is it a cold, the flu or a stomach bug?”

  1. […] See my previous post on differentiating between colds, influenza and stomach bugs here. […]


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