Travellers' Diarrhoea

What causes it

• Bacteria — around 80% of cases. Enterotoxigenic E. coli is the leading culprit, followed by Campylobacter, Salmonella and Shigella
• Viruses — norovirus and rotavirus. The classic cause of an outbreak sweeping a cruise ship or a hotel
• Parasites — Giardia, Cryptosporidium, Entamoeba. Less common, longer incubation, and the usual cause of diarrhoea that will not stop

How you get it

Contaminated food and water. In practice, food handled by someone who did not wash their hands is a bigger risk than the water supply — which is why bottled water alone is not much protection.

Highest-risk items: salads and raw vegetables, unpeeled fruit, buffet food kept warm, ice, unpasteurised dairy, undercooked meat and shellfish, and food from street vendors with no turnover.

Higher-risk destinations

South Asia, sub-Saharan Africa, parts of Central and South America, and parts of South East Asia and the Middle East.

Who is more likely to get it, or to get it badly

• Young adults — partly behaviour, partly adventurousness with food
• Young children and older travellers, who dehydrate faster
• People taking a proton pump inhibitor — stomach acid is a defence, and suppressing it measurably increases risk. Rarely mentioned, and worth knowing if you take omeprazole daily
• People with inflammatory bowel disease, diabetes, or immunosuppression
• Anyone visiting friends and relatives in their country of origin — consistently a higher-risk group, because home cooking feels safe and pre-travel advice is often skipped

The resistance problem worth knowing about

Travel to South Asia in particular carries a substantial chance of picking up resistant gut bacteria — ESBL-producing organisms — and taking antibiotics while there makes that considerably more likely. Most people carry them harmlessly for months and clear them. It matters because it is one of the real arguments against treating mild traveller's diarrhoea with antibiotics.

Most traveller's diarrhoea needs no test at all. It is diagnosed from the history, and a video consultation is well suited to it — including while you are still abroad.

What we establish

• Where you travelled, and when you got back — the first question, always, because of malaria
• How many stools a day, and whether there is blood or mucus
• Fever, and how high
• How much you are managing to drink, and how much you are passing urine — which is what actually determines how worried we are
• How long it has gone on — the two-week mark changes the approach entirely
• Malaria prophylaxis: what you took, and whether you completed it after returning
• Vaccinations, and any antibiotics taken abroad
• Other conditions and medication, including immunosuppressants and PPIs

When testing is warranted

• Stool testing for anything lasting more than 14 days — including specific testing for Giardia and other parasites, which routine culture misses. Note that three separate samples are traditionally needed for parasites, as shedding is intermittent
• Blood or mucus in the stool
• Fever with diarrhoea after travel
• Diarrhoea in an immunosuppressed traveller
• Full blood count, kidney function and inflammatory markers where someone is unwell or dehydrated
• Coeliac screening where symptoms persist — coeliac disease genuinely can be unmasked by a gut infection, and a "never right since that holiday" story is a recognised presentation

What must not wait for a remote consultation

Fever after travel to a malaria area requires a blood film the same day. That is a hospital or urgent care attendance, not a video call. We will say so plainly and direct you there rather than arranging anything ourselves.

Severe dehydration, blood with high fever, and severe abdominal pain also need in-person assessment.

What actually works

• Hand hygiene is the measure with the best evidence — soap and water, or alcohol gel, before every meal and after the toilet. It outperforms every food rule
• Carry alcohol gel, and use it before you eat with your hands

Food and water — sensible, but weaker than people assume

"Boil it, cook it, peel it, or forget it" is reasonable advice, and studies show people who follow it strictly still get ill at similar rates — because contamination usually comes from the hands that handled the food. Worth doing, but do not rely on it alone:

• Bottled water with an intact seal, or water boiled, filtered or chemically treated
• Avoid ice — frequently made from untreated water, and freezing does not sterilise it
• Brush your teeth with bottled water where the supply is unsafe
• Eat food that is freshly and thoroughly cooked and still hot
• Fruit you peel yourself
• Avoid buffets held lukewarm, unpasteurised dairy, and raw or undercooked shellfish
• Busy street stalls with rapid turnover are often safer than quiet restaurants, because the food has not been sitting

Before you go

• Take a standby pack: oral rehydration sachets, loperamide, and where appropriate a standby antibiotic with written instructions
• Get travel vaccinations sorted — typhoid, hepatitis A and cholera where indicated. Note these do not prevent ordinary traveller's diarrhoea, which is a common misunderstanding
• Take malaria prophylaxis exactly as prescribed, and finish the course after you come home. Stopping early is one of the commonest reasons people develop malaria despite taking tablets
• Travel insurance that actually covers medical treatment, and know how to use it
• If you take a proton pump inhibitor, ask whether you still need it — it raises your risk

Probiotics and bismuth

Evidence for probiotics in prevention is weak and inconsistent — harmless, but do not rely on them. Bismuth subsalicylate has modest evidence but requires frequent dosing and turns the tongue and stools black, which alarms people who were not warned.

While you are ill

• Rest, and keep drinking — more than feels necessary
• Wash your hands scrupulously, particularly before handling food for others. Norovirus in particular spreads through a family or a tour group very fast
• Do not go swimming for two weeks after cryptosporidium, which survives chlorination
• If you work in food handling or healthcare, stay off work until 48 hours after the last episode — a legal requirement in many roles, not just good manners. We can provide a sick note

Do I need antibiotics?

Usually not. Most traveller's diarrhoea settles in three to five days with rehydration alone, and antibiotics shorten it by around a day at the cost of side effects and picking up resistant gut bacteria. They are worth taking for moderate to severe illness, or with fever and blood. For a mild upset that lets you carry on with your day, fluids are the better answer.

Can I take Imodium?

Yes for ordinary watery diarrhoea, and it is genuinely useful before a flight or a long journey. Do not take it if there is blood in the stool or a high fever — slowing the bowel when the infection is invading the gut wall can cause serious complications. Not for young children without advice.

I've got a fever since I got back. Is that just the bug?

Treat it as malaria until a blood test says otherwise if you have been anywhere malarious in the past year — even if you took your tablets, and even if the main symptom is diarrhoea and vomiting. Malaria is regularly mistaken for gastroenteritis, and it can kill quickly. Go the same day, and tell them where you travelled.

It's been three weeks and it hasn't stopped.

That is no longer ordinary traveller's diarrhoea. The commonest causes are giardia — bloating, wind, greasy floating stools, sulphurous belching — and post-infectious IBS. It needs stool testing including specifically for parasites, which standard culture misses, rather than another antibiotic course. Coeliac disease is occasionally unmasked this way too.

Will bottled water protect me?

Partly. It helps, but most traveller's diarrhoea comes from food handled by unwashed hands rather than from the water supply — which is why people who drink only bottled water still get ill. Hand hygiene has better evidence than any food or water rule. And avoid ice, which is usually made from tap water.

Do travel vaccinations prevent it?

No, and this is a widespread misunderstanding. Typhoid, hepatitis A and cholera vaccines protect against those specific diseases. They do nothing for the E. coli and campylobacter behind most traveller's diarrhoea. Worth having for their own sake; not a reason to relax about food.

Should I take antibiotics with me just in case?

For higher-risk trips, yes — as a standby pack with written instructions on when to use it, not something to start at the first loose stool. That is far safer than buying an unidentifiable antibiotic abroad, where counterfeit and inappropriate medicines are a real problem. Worth arranging at a pre-travel consultation.

Can I still fly?

Usually, if you are not dehydrated and can manage the journey — loperamide helps for the flight itself. Do not fly if you are significantly dehydrated, feverish, or passing blood; get assessed first. And if you work in food handling or healthcare, you must stay off work until 48 hours after your last episode.