My eight-year-old daughter woke up with a high temperature and bloody diarrhoea. This was the infection to blame, how she picked it up while swimming… and why experts now warn of a ticking timebomb

Aisling McCarthy had no reason not to let her eight-year-old daughter, Keeva, swim at their local beach during this year’s August heatwave. The sea at Avon Beach in Dorset, where the family live, carried the Environment Agency’s highest ‘excellent’ water-quality rating.

So when Keeva was hit by a wave and came out spluttering after swallowing ‘quite a lot of water’, Aisling didn’t give it a second thought, she told the Daily Mail: ‘We had an ice cream – and went home.’

But two days later, Keeva was so lethargic that, out of character, she had to be woken up in the morning.

The family (including father Adam and twin sister Cornelia) were setting off on a camping trip to Devon, but Keeva refused to eat breakfast and slept for almost the entire journey. The following day her temperature was above 39C (102F) and she’d developed constant diarrhoea.

‘It wasn’t a typical stomach bug I’d seen in my children before,’ says Aisling.

‘I was carrying her everywhere as she was so lethargic. Normally, I could control a temperature with Calpol, but it would come down and then she was burning up again.’

The day after, ‘I noticed there was blood in her stool, and I panicked,’ Aisling recalls – and the family raced to A&E, where Keeva was admitted. She was so dehydrated she was put on a drip and diagnosed with a viral infection. Fortunately, she began to improve and was discharged two days later.

But results of tests later revealed she had campylobacteriosis, a bacterial infection that can be contracted from contaminated food or water. It took around two weeks for Keeva’s appetite to return and, a month on, she’s still not back to full strength, says Aisling. When she contacted the local council about the quality of the water, it responded by asking whether the family had been to any food festivals – ‘which we hadn’t’.

Aisling found this frustrating because Keeva eats very little meat and the campylobacter bacterium is often associated with eating undercooked chicken; and her twin sister had not become ill. ‘I couldn’t think of a food she may have had individually that would have caused it,’ she says.

She suspects Keeva’s illness was related to her swim. Keeva’s case exposes a worrying gap in the UK bathing water system. Although Avon Beach was officially rated ‘excellent’, routine checks do not test for campylobacter.

Indeed, experts are warning that the tests used to award these reassuring grades are too narrow.

In England, the Environment Agency grades bathing waters – such as beaches and lakes – according to levels of two bacteria: E.coli, which can cause severe diarrhoea and, in serious cases, kidney failure; and intestinal enterococci, which can lead to urinary and skin infections.

The tests date back to World Health Organisation (WHO) guidance from 2003, which identified intestinal enterococci as a warning sign of faecal pollution and therefore a risk of illness in swimmers.

The EU added E.coli in tougher bathing-water rules introduced in 2006, which England still follows.

But what’s been left out is a host of other potentially dangerous bacteria, viruses and parasites found in sewage and animal faeces, say experts. As well as campylobacter, this includes salmonella, norovirus and the parasites giardia and cryptosporidium and adenovirus – which between them can cause vomiting, diarrhoea and agonising stomach cramps, as well as infections of the eyes, ears and airways.

Children and older people are particularly vulnerable because of their weaker immune systems.

Now figures exclusively revealed to the Mail suggest that more than half of the 1,279 swimmers (57 per cent) who reported becoming ill after swimming in rivers, lakes and seas between May and August this year had been at bathing waters officially rated ‘good’ or ‘excellent’.

According to the charity Surfers Against Sewage, in August alone more than 68 per cent of the 388 sicknesses reported that month came following visits to areas with good or excellent waters.

And the problem is getting worse, says the charity, which has received 1,645 reports of people becoming ill from bathing waters so far this year – already more than the 1,553 received during

the whole of 2025 (last year, almost three-quarters of those cases involved bathing waters rated good or excellent).

These illnesses included gastroenteritis and skin, ear and eye infections, while some needed hospital treatment.

Among the bugs that current tests don’t check for is vibrio, a bacterium usually found in warm subtropical waters, such as the Gulf of Mexico, which can cause severe wound infections and potentially fatal blood poisoning, killing around one in five of those infected, according to the US Centers for Disease Control and Prevention. But it’s becoming more common in British coastal waters as they get hotter owing to climate change, say experts.

Scientists found three times more vibrio in a coastal estuary in south-west England during the hot summer of 2018, according to a 2020 study in Environmental Microbiology Reports. Water temperatures at the estuary reached 32.1C, compared with an average of 18.7C the following summer.

The researchers warned that during heatwaves, low-salt estuaries could become ideal breeding grounds for vibrio, similar to the Baltic Sea, which also has low salt levels and where infections are already established.

Indeed, in that hot summer of 2018, 492 vibrio infections were recorded across six northern European countries, including Germany and Sweden, more than three times the usual number. (While data is still being collected for 2026, already Germany had reported 17 cases by July, including two deaths following visits to the Baltic Sea.)

The British researchers who gathered the data warned that, as the climate warms, potentially dangerous vibrio in UK estuaries would provide a ‘clear human health risk’.

The Met Office reported in July that some seas around Britain were four to five degrees warmer than normal, raising concerns that this bacteria is on the rise again – yet no one is testing for it.

Now experts, including one who helped draw up the latest WHO water quality guidelines, are calling for water testing in the UK and Europe to be updated to reflect such emerging risks.

‘Although official bathing water quality has improved, the odds of illness among water users compared with non-water users remain similar to those reported around 30 years ago when bathing-water rules were far less strict,’ says Anne Leonard, a senior environmental epidemiologist and microbiologist at the University of Exeter, whose own research – published in 2020 – has shown this.

Back then, beaches could be deemed safe to swim in with up to 2,000 faecal bacteria per 100ml.

Today, to get an ‘excellent’ rating E.coli levels must be just 250 per 100ml and for intestinal enterococci, 100 per 100ml. A ‘good’ rating allows 500 and 200, respectively.

For inland bathing waters such as rivers and lakes, the limits are double that: 500 E.coli and 200 enterococci per 100ml for ‘excellent’; and 1,000 and 400, respectively, for ‘good’.

Anne Leonard says one possible reason why more exacting standards haven’t led to a reduction in infections is that the official tests don’t look for the viruses and bacteria that are making swimmers ill.

E.coli and intestinal enterococci are useful warning signs of recent faecal pollution, she says, but ‘may not always correlate well with important human pathogens, particularly viruses’, such as norovirus and rotavirus (which also causes diarrhoea and vomiting) ‘which may persist through wastewater treatment and in the environment’.

The WHO and the Environment Agency say that testing every water sample for every possible disease-causing bug would be slow and expensive.

Instead, intestinal enterococci are used as warning signs that faecal pollution has entered the water – and therefore there’s a broader risk that other bugs and viruses will have, too.

But scientists are now questioning that assumption.

A review published last year in the Journal of Water and Health, which examined nine studies looking at illness linked to swimming – eight in the sea and one in fresh water, mainly in the US – concluded that relying on E.coli and intestinal enterococci alone ‘may not be sufficient to protect health’.

Eight of the studies found that swimmers were more likely than non-swimmers to suffer diarrhoea and vomiting, or ear, eye, skin and breathing problems – and the researchers, from Griffith University in Australia, found that swimmers were becoming ill even when the usual E.coli and enterococci tests suggested the water was safe.

And as Professor Sunny Jiang, a water-quality expert at the University of California, points out: ‘E.coli and enterococci levels could either under-predict or over-predict the presence of human enteric viruses [viruses that infect the gut and are shed in faeces, such as norovirus].’

In other words, high bacterial readings do not reflect the concentration of viruses in the water.

More worryingly, low readings give swimmers false reassurance.

Evidence that these other bugs are causing illness includes 184 people reporting sickness and diarrhoea after bathing at a lake in Cardiff in 2024 – most of those then tested were found to have norovirus, a highly infectious vomiting bug that can spread through water contaminated with faeces.

In 2025, the UK Health Security Agency (UKHSA) recorded 115 cases of leptospirosis in England, a potentially serious bacterial infection caught from water contaminated with the urine of infected animals. Stephen Alcock, a 68-year-old retired aeronautical engineer from Derby, nearly died from it after water splashed into his face while he removed a fallen branch from a fishing lake in October last year. Six days later he developed nausea, exhaustion and aching legs. His GP initially suspected gastroenteritis.

By day ten Stephen could no longer walk and his skin and eyes had turned yellow with jaundice. Within hours of an urgent admission to hospital, his liver and kidneys were failing. He was transferred to ICU, where he needed breathing support and dialysis. His family were warned he might die.

Tests confirmed leptospirosis and sepsis. Stephen spent five weeks in hospital, lost 14kg (2st 3lb) and had to learn to walk again. His kidneys have not fully recovered, and he has to be monitored every six months. ‘I was unlucky to contract leptospirosis, but very lucky to be alive,’ he told Good Health.

Professor Jiang believes routine testing should also look for coliphages, a type of virus that doesn’t infect humans but targets bacteria – as this can act as a warning that water has been contaminated with faeces more reliably than one of the usual tests.

A study published last month found that coliphage levels, along with E.coli, more reliably predicted rates of diarrhoea or vomiting in swimmers in four Hungarian rivers and lakes (which met EU standards) than levels of intestinal enterococci (one of the two bacteria used in England’s bathing-water tests) – which failed to predict an increase in illness.

For each tenfold increase in E.coli, the risk of gastrointestinal illness rose by around 73 per cent, while high levels of coliphages increased the risk by 45 per cent, reported the researchers from the University of East Anglia. Enterococci are a less reliable warning of stomach illness because E.coli and coliphages can survive for longer, explains Paul Hunter, a professor in medicine and director of the National Institute for Health and Care Research Health Protection Research Unit in Gastrointestinal Infections, who led the analysis.

Even a leading expert involved in producing the water-testing protocols is now questioning them.

Dr Joao Brandao, an environmental health scientist at the National Health Institute Doutor Ricardo Jorge in Portugal, helped develop the WHO’s latest recreational-water guidance published in 2021 – it retained intestinal enterococci as its main warning sign of faecal contamination, but he says not testing for more bacteria and viruses is now a major weakness.

He told Good Health he no longer fully supports the ‘latest WHO guidelines’ and checking ‘only for faecal pollution’ because new evidence and faster testing methods have since emerged. ‘Vibrio and other pathogens are not in the regulations as things that must be looked for, and this is just wrong.’

He adds that future checks should also look for ‘emerging infectious pathogens [eg Candida auris], antibiotic-resistant genes, microbial toxins and threats that are not necessarily associated with faecal pollution from faeces [eg, Staphylococcus aureus].’

Candida auris can cause dangerous bloodstream and organ infections and can be resistant to antifungal drugs. Microbial toxins produced by algae can cause rashes, vomiting, breathing problems and, in severe cases, liver or neurological damage. Staphylococcus aureus can cause skin and wound infections.

Another problem with water testing is that officials such as the Environment Agency do not test the water every day – for instance, it takes between five and 20 samples, depending on the site, across the entire bathing season (from May 15 to September 30).

Yet conditions can change within hours, says Professor James Ebdon, an environmental microbiologist at the University of Brighton. Heavy rain can wash manure from fields into rivers, overwhelm drains and trigger sewage overflows. A sample collected on a clean, dry morning may therefore reveal little about the water that swimmers encounter after a downpour several days later.

Indeed, in 2024 the Office for Environmental Protection warned that testing at one fixed spot can miss pollution elsewhere at the same bathing site, as sewage, farm run-off and other contamination is moved by rivers, wind and tides.

Worryingly, Avon Beach, where Keeva swam, is just a few hundred metres from the mouth of Christchurch Harbour, which environmental campaigners have dubbed the ‘toilet bowl of Bournemouth’ because large volumes of untreated sewage are discharged into the River Stour and carried into the harbour.

On August 19, just a few weeks after Keeva became sick, the Christchurch Harbour and Marine Society recorded 370,000 E.coli per 100ml in the Stour. The readings were so high that a junior sailing week was cancelled. That month, three-year-old Ivy Foster became seriously ill with E.coli after paddleboarding with her family in Christchurch Harbour. The infection was resistant to several antibiotics and she was admitted to hospital twice with vomiting and diarrhoea.

Her mother Kimberley said at the time she was so ill ‘I thought she was going to die’.

An Environment Agency spokesman said: ‘During the bathing water season, 464 designated sites benefit from water quality monitoring by the Environment Agency, allowing the public to make informed decisions about when and where to enter the water should they choose to do so.

‘We urge members of the public to follow UKHSA safety advice and to always check our Swimfo website for the latest information.’

Keeva’s family say her illness has taken away all enjoyment of the water. ‘We don’t even paddle any more,’ says Aisling. ‘We moved here for the beach and its natural beauty and this has been ruined in front of us.‘

A spokesperson for Bournemouth, Christchurch and Poole Council said they were ‘pleased that Keeva has recovered from her illness’. ‘We cannot comment on individual cases, but it is very difficult to trace back the cause of infection. We have had no notification from the UKHSA of other infections.’