What is stomach flu?

Written by: Dr Aathavan Loganayagam
Edited by: Bronwen Griffiths

Stomach flu, or gastroenteritis as it’s called by doctors, generally refers to a viral infection that causes an irritated and inflamed stomach and gastrointestinal tract. Despite the name, the stomach flu has nothing to do with the regular flu (influenza); they’re completely different ailments that affect completely different parts of your body. Whilst stomach flu causes nausea, vomiting and diarrhoea, influenza (“the flu”) causes body aches, headaches, fevers, and cold-like symptoms, such as a sore throat or a runny nose. Dr Aathavan Loganayagam, a top gastroenterologist, explains the causes, symptoms and treatment of stomach flu.

What are the causes of stomach flu?

Gastroenteritis is usually caused by viral infection, however, it can also come about as a result of food poisoning. Particular care should be taken when in countries with poor sanitation, as contaminated water and food can easily cause gastroenteritis.

Stomach flu can affect an individual, but it spreads easily through food and water, making large-scale infections entirely possible. The stomach flu can rip through workplaces or schools in particular with ease, under the right circumstances. Nursing homes and aged care facilities are also particularly susceptible to outbreaks due to the high numbers of people with a lowered immune system, living close together in a small space.

However, the stomach flu isn’t solely a viral ailment. At the base level, gastroenteritis is simply an inflammation of the stomach and gastrointestinal tract, and that can be caused by a number of non-viral factors from an individual’s diet and lifestyle. Non-contagious gastroenteritis can be caused by caffeine, food allergies, or otherwise harmless medications, such as antibiotics and aspirin.

While the non-contagious causes are impossible to completely guard against, the best way to prevent viral or bacterial gastroenteritis is maintaining high hygiene standards at home, school and at work, and making sure all food you eat is prepared and handled carefully.

What are the symptoms of stomach flu?

Stomach flu symptoms will often appear within two days after contact with the virus and can include (but are not limited to) the following:

Non-specific stomach flu symptoms include:

  • A fever above 37°C
  • Clammy skin or sweating
  • Pain in the joints and muscles
  • Weight-loss
  • Poor feeding (in children)
  • Headaches
  • Fatigue

Frequent vomiting and diarrhoea can result in severe dehydration, which can be dangerous and even fatal in some cases. This can be the most debilitating aspect of the illness. Symptoms of severe dehydration include:

  • Weakness
  • Confusion
  • An elevated heart rate
  • Producing very little urine
  • Muscular cramps

If severe dehydration is suspected, immediate medical attention is crucial. Trying to rehydrate the patient and taking them to the doctor or the emergency room at your local hospital should be your first move if you see the symptoms of severe dehydration.

Treatments for stomach flu:

There’s not much you can do in terms of treating or preventing most of the stomach flu’s symptoms, so the main focus when treating gastroenteritis is preventing dehydration. To achieve this, it’s crucial that the body has enough fluids and minerals. Vomiting and diarrhoea cause the loss of fluids and electrolytes, so drinking extra fluids is crucial.

An electrolyte-replenishing drink is ideal for older children and adults, but not for younger children. Younger children should drink an electrolyte and fluid replacement solution available at chemists. Don’t consume anything high in sugar, as this will make certain symptoms worse, and won’t work towards replacing lost minerals.

It’s recommended that you drink between 60ml to 120ml of water every half an hour or so. Don’t try and ingest more than this, as it may cause vomiting or worsen the nausea.

Young children and infants with gastroenteritis are at the greatest risk of severe hydration and subsequent death, so parents should seek immediate medical attention and stay vigilant in monitoring the amount of fluids going in and out of their child.

Stomach flu duration:

The stomach flu illness will usually appear and disappear in the space of a few days without treatment. However, the stomach flu can hang around for as long as 10 days, which can be incredibly dangerous, as staying adequately hydrated while sick gets harder over a longer period. Complications from severe dehydration can increase the amount of time the body takes to recover from the stomach flu and lead to conditions that end up causing more trouble and discomfort than the original gastroenteritis.

While gastroenteritis can be an extremely unpleasant experience for those affected, the stomach flu’s duration is usually quite short. So, as long as you remember to stay sufficiently hydrated, you should get through it with minimal stress and discomfort.

By Dr Aathavan Loganayagam

Dr Aathavan Loganayagam trained in medicine at Guy’s, King's and St. Thomas’ medical schools. He then underwent rigorous structured specialty training in gastroenterology and general internal medicine in the well respected South London training programme.

He then spent two years during postgraduate training as a research and endoscopy fellow at Guy’s and St Thomas’ Hospitals, London. His research was in the fields of pharmacogenetics, inflammatory bowel disease and gastrointestinal malignancy. He has received awards and grants for outstanding research work, including the prestigious NHS Innovation London Award.

Dr Loganayagam has numerous publications in peer reviewed journals on all aspects of gastroenterology. He is actively involved in clinical research. He has particular local expertise in the practice of personalised medicine and the utilisation of novel therapeutic agents in the treatment of complex inflammatory bowel disease. He is currently the lead clinician for endoscopy at Queen Elizabeth Hospital, Woolwich.

Diagnostic and advanced therapeutic endoscopy remains a major part of his clinical expertise, including assessment and treatment of inflammatory bowel disease, strictures, polyps and cancers.

Dr Loganayagam is an approachable doctor who takes pride in his communication skills with patients. He is keen to ensure that patients are fully informed and involved in all aspects of their care.

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