In Hong Kong, outbreaks of acute gastroenteritis (AGE) have seen a significant increase, particularly at the start of 2025 . This has made it increasingly important for residents to maintain good personal hygiene, environmental cleanliness, and food safety to prevent the spread of this common illness. With gastroenteritis being highly contagious, understanding its causes and how to avoid it is crucial for safeguarding both personal and public health.

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What is Acute Gastroenteritis?

Acute gastroenteritis is the inflammation of the stomach and intestines that leads to symptoms such as vomiting, diarrhea, abdominal pain, and sometimes fever . This infection is primarily caused by viruses and bacteria, both of which can result in food poisoning or stomach flu. Acute gastroenteritis is an umbrella term for various forms of gastrointestinal infections, which can be classified into four categories: viral gastroenteritis, bacterial gastroenteritis, parasitic gastroenteritis, and non-infectious gastroenteritis. Each type has its unique causes, symptoms, and treatment approaches.

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Viral Gastroenteritis

Viral gastroenteritis, commonly referred to as stomach flu, is one of the most common causes of gastroenteritis worldwide. It primarily causes watery diarrhea, stomach cramps, nausea, and vomiting, with a mild fever sometimes accompanying the infection. This type of gastroenteritis is transmitted through contact with contaminated individuals or by consuming contaminated food or water. The two most prevalent viruses that cause viral gastroenteritis are Norovirus and Rotavirus.

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Norovirus

Norovirus is the leading cause of foodborne illness globally, accounting for over 60% of foodborne diseases and 95% of nonbacterial acute gastroenteritis . It is contagious, particularly in confined spaces such as cruise ships, schools, and hospitals. In Hong Kong, it is one of the key contributors to outbreaks of acute gastroenteritis, particularly in crowded environments. Symptoms of norovirus typically include nausea, vomiting, diarrhea, and stomach cramps.

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Rotavirus

Rotavirus is the most common cause of viral gastroenteritis in children. It spreads primarily through contaminated hands, surfaces, or food, especially in schools and daycare settings. The incidence of this infection in children has been significantly reduced by the rotavirus vaccine, which involves administering two doses of the vaccine separately to babies at 8 and 12 weeks old.Although adults can contract rotavirus, they often do not show symptoms, but can still spread the infection. Older adults are more vulnerable as their immune systems weaken with age.

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Are There Treatments for Viral Gastroenteritis?

There are no specific treatments for viral gastroenteritis, as antibiotics are not effective against viral infections. The primary treatment one can take is self-care, which includes staying hydrated, especially with oral rehydration solutions (ORS), and avoiding alcohol, caffeine, and other irritants that can dehydrate the body, until recovery is achieved.

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Bacterial Gastroenteritis

Bacterial gastroenteritis occurs when harmful bacteria infect the digestive system and is less common than viral gastroenteritis. Common symptoms include vomiting, diarrhea, and abdominal pain, often accompanied by fever. Bacterial gastroenteritis is usually caused by either E.coli or Salmonella.

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E.coli

E. coli is a dangerous cause of bacterial gastroenteritis, which can lead to severe conditions that may result in kidney failure. The symptoms of E.coli infection include bloody diarrhea, which may last for several days, vomiting and nausea, which make hydration difficult, and severe stomach cramps. E. coli is primarily spread through contaminated food, such as undercooked meat and untreated water.

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Salmonella

Salmonella is another common bacterial cause of gastroenteritis, usually contracted from contaminated water or food. It is typically found in undercooked poultry, eggs, and dairy products. The symptoms of Salmonella are similar to those of E.coli, which include bloody diarrhea, fever, and abdominal cramps. To prevent Salmonella, it is advised to cook poultry thoroughly to an internal temperature of 74°C.

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Parasitic and Non-Infectious Gastroenteritis

Parasitic gastroenteritis is caused by parasites that infect the gastrointestinal tract. These parasites are typically transmitted through contaminated water sources, including recreational water like pools, lakes, or rivers, where proper sanitation is not maintained. People who travel to areas with poor sanitation or limited access to clean drinking water are at a higher risk of contracting parasitic infections, especially if they consume untreated water or food that has been contaminated by it. Individuals who do not wash their hands properly or fail to follow proper hygiene practices before preparing and eating food are also susceptible to parasitic gastroenteritis.

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Unlike infectious forms of gastroenteritis, non-infectious gastroenteritis isn’t caused by bacteria, viruses, or parasites. Instead, it stems from factors like chemical irritants, allergic reactions, or physical triggers such as certain medications or alcohol consumption. Common triggers include caffeine, alcohol, spicy foods, and even stress.

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The symptoms of non-infectious gastroenteritis including nausea, vomiting, abdominal pain, and diarrhea, but do not require antibiotics. Managing this condition typically involves rest, staying well-hydrated, and avoiding the specific irritants or triggers that initially caused the symptoms. By making a few lifestyle adjustments and paying attention to dietary and environmental factors, most people can recover without the need for medical intervention.

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Beat Acute Gastroenteritis: Protect Yourself and Others

Acute gastroenteritis is a common illness that can be caused by viruses, bacteria, parasites, or non-infectious factors, each requiring different prevention and treatment approaches.

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While most cases can be managed with hydration and rest, it’s essential to seek medical attention if symptoms are severe, especially for vulnerable groups. Understanding the causes of gastroenteritis and taking preventive steps can help protect your health and prevent the spread of the illness to others. By adopting simple habits, such as proper hand-washing and safe food handling, we can significantly reduce the impact of all forms of gastroenteritis.

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Source:

1.The Government of the Hong Kong Special Administrative Region Press Releases. (2025). CHP urges public to be vigilant in preventing acute gastroenteritis. Retrieved from https://www.info.gov.hk/gia/general/202501/08/P2025010800580.htm

2.Cleveland Clinic. (N.D). Gastroenteritis. Retrieved from https://my.clevelandclinic.org/health/diseases/gastroenteritis

3.National Library of Medicine. (2013). Epidemiology, Prevention, and Control of the Number One Foodborne Illness. Retrieved from https://pmc.ncbi.nlm.nih.gov/articles/PMC7126578/

4.Mayo Clinic. (2013). Viral gastroenteritis (stomach flu). Retrieved from https://www.mayoclinic.org/diseases-conditions/viral-gastroenteritis/symptoms-causes/syc-20378847

5.Healthline. (2022). What to Know About Parasitic Gastroenteritis. Retrieved from https://www.healthline.com/health/parasitic-gastroenteritis

6.Healthline. (2024). What’s the Difference Between Noninfectious Gastroenteritis and Colitis?. Retrieved from https://www.healthline.com/health/noninfectious-gastroenteritis-and-colitis