Cholera

Cholera is a gut infection that drains fluid faster than any other cause of diarrhoea. The bacterium behind it, Vibrio cholerae, settles in the small intestine and releases a toxin that forces the lining cells to pump water and salts into the bowel. The lining itself is not destroyed, there is no blood in the stool and there is usually no fever — the body simply dries out from the inside at speed. That explains the defining feature of the illness: what kills is not the infection as such but dehydration, and the same feature makes cholera one of the very few lethal infections that can usually be stopped by drinking the right thing. Cholera does not circulate in Europe and imported cases are rare, but anyone travelling to an area with an outbreak is better off knowing how it works.

How the bacterium gets in

Infection happens through the mouth, in water or food contaminated by a sick person's stool. The classic route is drinking water from a source that sewage runs into. Less often the culprits are raw or undercooked shellfish and fish from polluted coastal waters, salad leaves and vegetables washed in that water, ice made from it, or ready-made food handled with dirty hands. Ordinary contact carries no risk: talking, shaking hands or sharing a bus with someone who is ill will not pass cholera on.

You have to swallow a large number of bacteria to fall ill, because stomach acid destroys most of them. The risk is therefore higher for anyone whose acid is reduced: people on long courses of proton pump inhibitors, people who have had stomach surgery, and small children. Illness also tends to be more severe in people with blood group O, although anyone can catch it.

Outbreaks are almost always tied to places where the water supply has broken down: refugee camps, districts hit by flooding or an earthquake, crowded neighbourhoods without sanitation. A tourist staying in a hotel with bottled water faces an incomparably smaller risk than an aid worker in the very same city.

How the illness begins

The gap between infection and the first signs runs from a few hours to five days, most often two or three. An important detail: most people who pick up the bacterium notice nothing at all, or have mild diarrhoea indistinguishable from any other. The severe form develops in roughly one person in ten, and it is that form which gave the disease its reputation.

Cholera diarrhoea is painless and extremely heavy. The stool quickly loses its normal character and turns cloudy and whitish with flecks in it, which is why it is described as looking like the water rice has been rinsed in. There is no griping and no cramping, so people sometimes assume right up to the end that their stomach is merely upset. Vomiting often joins in, without any nausea beforehand. An adult at the peak of the illness can lose up to a litre of fluid an hour, so dehydration builds over hours rather than a day: a dry mouth, sunken eyes, skin that has lost its spring, cramp in the calves, urine that darkens and then stops, falling blood pressure and weakness that verges on fainting.

When help is needed at once

The danger here is the speed. Untreated severe cholera can kill within hours; when fluid is replaced in time, fewer than one person in a hundred dies. The distance between those two outcomes is measured in hours, not days.

Call the emergency services if you see, in yourself or in someone close to you:

• heavy watery diarrhoea that will not stop, especially together with vomiting;
• an inability to keep any fluid down;
• no urine for more than eight hours, or a dry nappy for half a day in a small child;
• sunken eyes and, in a baby, a sunken soft spot and crying without tears;
• cold clammy skin, a fast weak pulse, dizziness on standing up;
• confusion, or drowsiness that is hard to rouse someone from.

Always tell the medical team that you have recently returned from a trip, and name the country, even if several days have passed and you have been home in between. That one sentence changes the whole direction of the assessment.

What the treatment is

The mainstay is water with salts and sugar in exactly the right proportion — in practice, a ready-made oral rehydration solution from a pharmacy. Plain water, tea or sweet fizzy drinks will not do the job: they do not replace the sodium and potassium that have been lost, and sugary drinks can even make the diarrhoea worse. Drink after every loose stool, in small sips and continuously rather than only when thirst prompts it; if there is vomiting, take small amounts very often.

If someone can no longer drink, or has lost too much already, fluid and salts are given into a vein. That is done in hospital, and in the severe form it is the drip that saves the person. Antibiotics play a supporting role: they shorten the diarrhoea and the period during which someone is infectious, but they do not replace drinking. The drugs used usually come from the tetracycline, macrolide or fluoroquinolone groups, and the choice depends on age, on pregnancy and on which resistance patterns dominate in the region. Children are also given zinc, which shortens the illness too.

What not to do is take medicines that slow the bowel down, such as loperamide. They do nothing about the central problem, fluid loss, and they hold the toxin inside. Eating is allowed and encouraged as soon as appetite returns, and breastfeeding should not be interrupted.

How to avoid bringing cholera home

It all comes down to what reaches your mouth. In areas where cholera occurs:

• drink only bottled water with an intact seal, boiled water or water you have disinfected, and clean your teeth with the same;
• skip ice in drinks, as it is rarely made from safe water;
• eat food that is hot and freshly cooked, and choose fruit you can peel yourself;
• avoid raw shellfish, oysters and lightly cured fish;
• wash your hands with soap and water before eating and after the toilet, and use an alcohol hand gel when there is no water.

A cholera vaccine exists, and it is swallowed rather than injected. Most travellers do not need it: an ordinary trip to a city or a resort carries almost no risk. It is worth discussing if you will be working at the centre of an outbreak, joining a humanitarian mission, or travelling through remote places with no access to medical care. Adults take two doses one to six weeks apart and young children take three; the course should be finished at least a week before departure. Protection is partial and lasts a limited time, so the vaccine does not remove the need for care with water and food.

Online consultation

Before a trip, a doctor online can help you judge the real risk of your particular route, tell you whether vaccination is worth discussing, and suggest what to pack — starting with rehydration salts, which are far harder to find abroad than at home. If diarrhoea has already begun, the doctor will go through what the picture looks like, help you work out how much to drink, and name the signs that mean going to hospital straight away rather than waiting until morning.

The online format suits assessing a situation, preparing for travel and going through test results after you return. Severe dehydration is treated only in person: a drip cannot be set up through a screen, and in that case the point of the consultation is to send you as quickly as possible to where you can be helped.

This material is for information only and does not replace medical advice.