Vibrio spp. is a group of bacteria that naturally live in rivers, lakes, and especially seawater. They tend to thrive in warmer coastal areas and are often linked to seafood and water quality. While many Vibrio are harmless, some species can cause illness in humans. People usually get sick by eating raw or undercooked seafood, like oysters, or by exposing open cuts to contaminated seawater.

Vibrio bacteria, especially Vibrio cholerae and Vibrio parahaemolyticus, can cause serious gut infections when people consume contaminated water or food. These bacteria attack the small intestine, leading to watery diarrhoea, stomach pain, nausea, and dehydration (Dabanch et al., 2023; Mthembu et al., 2021). Because diarrhoea flushes out not only water but also important electrolytes and beneficial gut microbes, infections with Vibrio spp. can leave the gut microbiome unbalanced and weaker than before. This imbalance makes it harder for the body to fight off other harmful germs and can cause lingering digestive discomfort even after the infection has passed (Siddique & Cash, 2014).

✔️ What it is: A group of bacteria found in water and seafood, with some species (like Vibrio cholerae and Vibrio parahaemolyticus) causing gut infections.

✔️ Where it’s found: Common in warm coastal waters, raw or undercooked seafood (especially shellfish), and sometimes in contaminated drinking water.

✔️ How it spreads: Usually through eating contaminated food or drinking unsafe water. Rarely, through open wounds exposed to seawater.

✔️ Main symptoms: Watery diarrhoea, stomach cramps, nausea, vomiting, and dehydration. In severe cases (V. cholerae), life-threatening fluid loss can occur.

✔️ Gut health impact: Infections disrupt the gut microbiome, flush out good bacteria, and weaken digestion, making it harder to fight off other illnesses.

✔️ Who’s most at risk: People with weakened immune systems, liver disease, or low stomach acid, as well as children and the elderly.

✔️ Prevention tips: Avoid raw or undercooked seafood, ensure safe drinking water, and wash hands after handling seafood or water sources.

✔️ Testing matters: Early detection can prevent severe dehydration, restore balance in the gut, and speed up recovery.

When Vibrio bacteria, such as Vibrio cholerae, enter the gut, the body’s first line of defence is the innate immune system. This includes the stomach’s acidic environment, protective mucus, and antimicrobial peptides that try to stop the bacteria from multiplying. If some bacteria survive, the immune system activates white blood cells and inflammatory signals to attack the invaders (Harris et al., 2012).

The adaptive immune system also plays a role, especially through antibodies such as IgA, which are produced in the gut lining. IgA helps block Vibrio bacteria from sticking to the intestinal wall and reduces toxin activity. Over time, this adaptive response creates a memory effect, meaning the body can respond more quickly to future infections. However, severe infections may overwhelm the immune system, leading to diarrhoea and dehydration, which highlights the importance of both natural immunity and medical treatment (Sack et al., 2004; Clemens et al., 2017).

Unhealthy levels of Vibrio spp. in the gut can cause a range of uncomfortable and sometimes serious symptoms. The most common are gastrointestinal issues such as watery or sometimes bloody diarrhoea, abdominal pain, nausea, and vomiting. These symptoms usually develop within 24 hours of infection and may last for a few days. In some cases, people may also experience fever and chills, as the body responds to the infection. While many cases resolve on their own, dehydration can occur quickly—especially in children, older adults, and people with weakened immune systems—making early attention important (Hosseini et al., 2022; Luo et al., 2020).

In more severe cases, particularly in people with underlying health conditions or compromised immunity, Vibrio spp. can lead to systemic infections where the bacteria spread beyond the gut. This may result in bloodstream infections (septicaemia), skin infections if there are open wounds exposed to contaminated water, and prolonged intestinal damage. Long-term disruption of the gut microbiome may also occur, weakening digestive and immune functions. Because these bacteria thrive in warm, aquatic environments and can be transmitted through contaminated food and water, monitoring gut health and preventing exposure are crucial steps in reducing health risks (Baker-Austin et al., 2018; Luo et al., 2020).

In early 2023, South Africa experienced a significant cholera outbreak caused by Vibrio cholerae, recording nearly 1,395 suspected cases and at least 47 deaths across all nine provinces by March 2024 (WHO, 2023). This surge highlighted the lethal impact of Vibrio species when public water and sanitation are compromised. Although cholera often steals the spotlight, other Vibrio species like V. parahaemolyticus and V. vulnificus are also known to cause gastroenteritis—commonly through the consumption of raw or undercooked seafood, especially shellfish (Qin, 2020).

Beyond acute outbreaks, V. cholerae and other vibrios disrupt gut health by inducing severe diarrhoea that damages the gut lining, dehydrates the body, and weakens the balance of beneficial gut bacteria. A balanced microbiome can help resist colonisation by these pathogens. Still, factors like malnutrition, poor immunity, or prior gut infections can compromise this resilience making South African individuals, particularly in areas with water and sanitation challenges, more susceptible to repeat infection and gut microbiome imbalance.

Keeping your gut strong and resilient is one of the best protections against infections like Vibrio spp. A healthy gut microbiome provides a natural barrier, helping to prevent harmful bacteria from taking hold. Diet plays a central role—eating foods rich in probiotics (like yoghurt, kefir, and fermented vegetables) and prebiotics (such as garlic, onions, and fibre-rich whole foods) can encourage the growth of beneficial bacteria that keep pathogens in check (Olaniran et al., 2015). Staying hydrated is also essential, especially since Vibrio infections often cause fluid loss through diarrhoea.

Good hygiene and safe water practices are equally important in the South African context, where Vibrio-related outbreaks are linked to contaminated water. Washing hands thoroughly, cooking seafood properly, and ensuring safe drinking water all reduce exposure risks (World Health Organization [WHO], 2023). For those who have already experienced gut infections, restoring balance through probiotic supplementation and nutrient-rich diets can help repair the intestinal lining and boost the immune system’s ability to fight off future threats (Raszl et al., 2021). Together, these steps strengthen both the gut and overall immune defences, offering protection against harmful Vibrio strains.