How to tell if you have stomach flu or food poisoning
Medical experts explain differences between the two, and how to ease symptoms of both
Recently, plagued with flu symptoms – coughing, sneezing, sore throat – I began to feel nauseous, too. When I began to vomit, I worried – had I eaten something bad?
I had hardly eaten for days, so it could not be food poisoning. It was clearly linked to whichever flu virus I was suffering from.
Gastroenteritis, inflammation of the stomach and intestines, is a broad term for conditions, usually with an infectious origin, that lead to gastrointestinal symptoms, namely vomiting and diarrhoea.
Hong Kong specialist in gastroenterology and hepatology Dr Paul Ng says the infection that triggers gastroenteritis can be bacterial, viral or, less commonly, parasitic.
Food poisoning
Bacterial gastroenteritis is usually caused by something you have eaten or drunk – contaminated food or water, say. Common bacteria that cause food poisoning include salmonella, E coli and listeria.
Salmonella is often carried in undercooked chicken; bird faeces may find their way into poultry during butchering.
E coli can be present in a host of foods, from undercooked hamburgers to raw milk, and including cheeses made from unpasteurised milk. Rarely, listeria is found in soft cheeses and salamis, and the resulting infection can cause miscarriage and stillbirth.
Stomach flu
Stomach flu is simply a viral gastroenteritis, Ng says, an extension of the viral infection that was causing the aches, pains and general malaise of regular flu in my case.
Viral gastroenteritis could be the result of a number of viruses such as norovirus, rotavirus and adenovirus. It is passed in much the same way as a cold – or Covid-19 – might be: through being in confined spaces, among lots of people, or from forgetting to wash our hands.
Gastroenteritis symptoms
Any infection – bacterial or viral, including flu – says Ng, “can affect the nervous system and cause disruption in the normal nervous and hormonal signals, leading to an upset in the normal regulation of the digestive system”.
Poor movement of food through the digestive system and inflammation of the stomach lining leads to microscopic changes, and sometimes swelling and bloating, that can cause nausea, vomiting and diarrhoea.
Hydration is key
Drinking water, fruit juice, tea or another liquid is imperative, as your body is losing a lot of fluid – often from both ends. Dehydration is a dangerous and even life-threatening condition and can come on quickly, especially in the very old and the very young. If a patient is severely unwell and unable to keep down liquids, they may need intravenous fluid replacement in hospital, and sometimes medication, including antibiotics.
Loss of appetite
Ng says: “It is important to make oneself drink even when there is no appetite for it.” Our appetite for food is often low when our gastric system is under attack, Ng says. The brain senses when the stomach is not functioning well, and sends signal not to load it with food.
Holistic nutritionist Sandra Carvajal agrees that when we are ill, our body’s energy is focused on healing. “The body … instinctively knows how to self-regulate,” she says. Digestion demands a lot of energy, which the body needs for healing when you have been unwell, she notes. Dialling back the appetite is your body’s way of prioritising maintaining energy levels.
“When you don’t eat, you feel tired, and if you allow your body to rest and sleep it supports healing,” she says. Then, once on the mend, the appetite returns because our body knows it needs – and is ready for – the nutrients to support recovery.