How to tell if it's a gastro bug or food poisoning

Flu season might be over but Gastro outbreaks are on the rise. Dr Sam Hay explains how to decode the tummy upsets that enter your home. 

This winter has been brutal! The worst flu season on record seems to finally be behind us. But then there were all the gastro outbreaks recently – an illness that smashed our house several times.

As the weather warms up and those holiday vibes kick in, we start venturing out to BBQs, parties, or just cheap and cheerful meals from local restaurants. And with that enthusiasm comes even more days spent cleaning up poo and spew, as rates of food poisoning climb.

So just what is the difference between food poisoning and 'gastro'?

There are many gastroenteritis infections, and many of them can originate from eating food. But classically we tend to group them into 'like' versions, and label them simple 'gastro' or 'food poisoning'.

A quick word on food poisoning: Food can lead to illness in many different ways. It can be contaminated with bacteria, viruses, parasites, or toxins. Then there's chemical contamination, allergies, or simply over eating.

But the classic 'food poisoning' relates to toxins. Food becomes contaminated with bacteria usually from the person preparing the food. They may not have worn gloves, washed their hands, or might have used the same knives and chopping boards for meat and salads. If the food is then left out at room temperature, the bacteria bubbles away producing lots of toxins, which spread throughout the food before it is eaten.

Once ingested, this toxin can immediately trigger an effect on us poor unsuspecting patients.

There are many gastroenteritis infections, and many of them can originate from eating food, says Dr Sam. Image: iStock 

Cause

Gastro

• Most commonly viruses
• Four predominate viruses: Rotavirus, Norovirus, Enteric Adenovirus, Astrovirus
• Some bacteria, for example: Campylobacter, Salmonella, E Coli

These bugs cause illness by either producing a toxin in our bodies after they have been ingested, or they literally invade and infect the lining of the bowel.

Food Poisoning

• Primarily toxin mediated
• Multiple culprits including: S aureus and Bacillus cereus

Spread

Gastro

• Various ways possible, the most common is the 'faecal-oral' route, from person-to-person. People just don't wash their hands after toileting. Bugs are then passed around easily.
• If food is undercooked, then bugs won't be killed off.

Food Poisoning

• Initial contamination of food from the person who prepared it.
• As illness is from a toxin, there is very low risk of person-to-person spread.

Initial contamination of food from the person who prepared it. Image: iStock 

Symptoms

Gastro

• Onset of symptoms takes a day or two to come on, and often builds up over hours.
• Watery diarrhoea is the primary symptom.
• Tummy cramps, nausea, and vomiting will be seen, but to varying degrees.

Food Poisoning

• Onset is sudden and dramatic, usually within 1-6 hours of ingestion.
• Nausea and vomiting predominate.
• Tummy cramps and diarrhoea tend to only occur occasionally.

Duration

Gastro

A few days. But maybe up to a whooping two weeks!

Food Poisoning

Generally comes and goes quickly over 24 hours.

Remember to keep the family hydrated when a tummy upset occurs. Image: iStock 

Diagnosis

Gastro

• Doctors will take a detailed history and conduct a thorough examination.
• Tests are not required for the vast majority of cases. But if symptoms persist they may ask you to send some stool samples off for testing.

Food Poisoning

• Circumstances are usually classic with this one
• Small clusters of people are often affected. For example, whoever ate one particular dish at the restaurant.
• Tests are next to useless, so doctors rely on a good history and examination.

Complications

The complications are the same regardless of the cause, but are more likely in babies and pregnant women.

Dehydration is by far and away the biggest issue with any gastroenteritis illness. Vomiting and diarrhoea cause a massive loss of water from the body. Plus, nausea and vomiting just makes it damned hard to drink enough.

The more dramatic the Ds and Vs, the faster dehydration will set in, so be on the watch out for the floppy, drowsy, listless kids (plus mums and dads!).

Some infections can cause other complications through the body such as brain infection, kidney failure, or persisting lactose intolerance.

Never underestimate the importance of washing your hands. Image: iStock 

Prevention

Prevention is certainly the key when it comes to these illnesses.

Food needs to be prepared and stored well, never left out in the open at room temperature for any longer than a couple of hours. In fact, as Aussie temperatures soar above 32 degrees, an hour is regarded as maximum – so be careful of those long grazing summer lunches.

Avoid cross-contamination by washing knives and chopping boards regularly, and keeping raw meats and other foods well separated.

Wash hands, wash hands, wash hands!

If the food looks dodgy – don't eat it! Poorly maintained foods in bain marie's are perfect brewing pots for bugs and their toxins. If food looks old or poorly looked after, then it's best to give it a miss.

Quarantine the sick ones.

Gastro spreads so well from dirty mucky hands covered in bug laden vomit or poo. Some bugs can even be spread through tiny droplets from coughs, sneezes or wayward vomit sprays (yuck!!!). So often the best strategy is to separate the sick ones from the rest of the family. And this includes making sure no one shares plates, cups, and drink bottles.

Remember, if you're concerned about anything presenting in your home - tummy bug or otherwise - speak to your local GP or healthcare professional.