Bali belly: managing travellers' diarrhoea, and when it stops being minor

The local name makes it sound like a Bali-specific curiosity. It is not. NaTHNaC describes travellers' diarrhoea as “the most common illness experienced by travellers, affecting over 20 percent of those who travel to high-risk destinations of the world”.

It “can be caused by viruses, bacteria or protozoa” — which is why no single prevention or treatment covers every case — and NaTHNaC is realistic about avoiding it: it is “difficult to prevent for those who cannot prepare their own food and drinks”. Following food and water hygiene advice is described as sensible, with the pointed addition that travellers “should always be prepared to manage the symptoms”.

That is the framing to take seriously for a long stay. The expectation is not that you avoid it, but that you are equipped when it happens.

Source: NaTHNaC / TravelHealthPro — Travellers' diarrhoea, read 3 October 2026

The first-line answer is fluid and electrolyte replacement, and NaTHNaC is specific about why the composition matters.

Oral rehydration solutions are recommended, diluted into clean drinking water, “to help to correct electrolyte (sugar/salt) imbalances”. A commercially available solution should be used because these carry “specific concentrations of sodium, potassium, and sugar”. NaTHNaC calls them “a useful item to have in a first aid kit for any trip” — worth packing before you need them, since the moment you do is a bad moment to go shopping.

Where none is available, NaTHNaC gives a fallback: six level teaspoons of sugar and half a teaspoon of salt to one litre of safe water.

It also notes symptomatic treatment with loperamide or bismuth subsalicylate. Those manage symptoms; the rehydration is what treats the actual risk, which is fluid loss.

This is where a lot of travel advice goes wrong, and NaTHNaC is unusually direct about it.

Travellers' diarrhoea is “usually a self-limiting condition and prescribing antibiotics for standby treatment should be carefully considered”. The reason is not caution for its own sake: travellers who take antibiotics “may acquire organisms that are resistant to antibiotics”, naming multi-drug-resistant Enterobacteriaceae and Clostridium difficile infections.

Standby antibiotics are reserved, following “a detailed risk assessment”, for people at high risk of severe illness, or those visiting high-risk areas in remote locations where access to medical care is limited.

That last clause is the one that applies to Indonesia specifically — not Seminyak, but Flores, Sumba, interior Kalimantan or a dive trip days from a hospital. It is a conversation with a clinician before you travel, and we are not going to publish a dose here. The decision belongs to someone who can assess you.

Most cases resolve on their own. The cases that do not are what cover exists for, and the trigger is usually dehydration rather than the infection itself — which is why the rehydration advice above is the whole first line.

Two things make Indonesia a different proposition from a fortnight's holiday:

Distance. Severe dehydration needs intravenous fluids, which means a facility. On Bali that is close; across most of the archipelago it is not, and the gap between stabilising care and adequate care is a transport question. Evacuation and repatriation is an optional add-on on the plans arranged here, not a standard benefit.

Exposure. A resident eats in the country every day for years. The 20% figure describes trips, not lifetimes.

On the cover question itself this is a clean case: an acute infection contracted after arrival, so neither pre-existing nor chronic. And worth knowing for most long-stay movers — Indonesia's national scheme reaches foreigners who have worked in the country for at least six months, so a retiree, a student or an accompanying spouse sits outside it entirely.