Gastroenteritis occurs when a person comes into contact with a causative agent which develops an inflammation of the gastro-intestinal tract. This can be caused not just by contaminated food, but also in some cases by anti-inflammatory drugs or antibiotics. It also may be as a result of a food allergy, which may present as nausea and vomiting, adominal pain and diarrhoea.
There are various bacteria that can cause gastroenteritis; shigella, salmonella, clostridium difficiel, staphylococcus, yersinia, salmonella, campylobacter jejuni. E coli is one that cause severe gastroenteritis, with patients often presenting with severe watery (non-bloody) diarrhoea and fever.
Gastroentiritis caused by viruses is frequently referred to as ‘stomach flu’ despite not being related to the influenza virus. Half of gastroetniritis is caused by norovirus, although this generally is prevalent in the period from October to April.
Rotavirus is more common in infants under one year old and is seasonal, as is the astrovirus which affects predominantly children and the elderly, whereas the adenovirus is not seasonal and generally affects children up to two years old.
Gastroenteritis can be caused by parasitic infections, generally Giardia. The parasite grows in the gut and symptoms of gastritis appear after about a week, but can last for a further six if not treated. Generally this would be treated with metronidazole. Cryptosporidium is another parasite that can cause gastroenteritis.
Care needs to be taken that the patient doesn’t become dehydrated; watching particularly for signs of dry mouth or tongue, drowsiness, dizziness or light-headedness, fainting, reduced urine output, lethargy or sunken eyes.