I’ve never thought that much about water. I’m vaguely aware I should drink more of it. But that’s about it. Like most people who have the luxury, I take it entirely for granted.

In Haiti everybody is thinking about water. All the time. Water here has suddenly started killing people. And it’s everywhere. Bucketing down in evening storms, lying in wait in puddles and dripping from broken taps.

So far this life-sustaining liquid – contaminated by the lethal cholera bacteria – has killed more than 800 people and left 12,000 sick according to the UN. And those are just the official statistics. Hundreds more people who may have lived too far away from medical help or didn’t know that this particular bout of vomiting and diarrhoea could kill them within hours if they didn’t get treatment could also be dead. And the numbers continue to rise.

Thankfully post-earthquake Haiti is a country packed with aid workers. Save the Children alone has more than 800 staff on the ground. Until last week, the skills and energy of thousands of doctors, nurses, and technical experts had prevented any major disease outbreak – an achievement given there are still more than 1.3 million people living in temporary camps where conditions are, at best, difficult, and, at worst, squalid.

But now there’s cholera – the most fast-spreading, virulent, and invisible of all water-born diseases. The outbreak can’t be described as a failing on behalf of the aid community – the first cases appeared in a rural area that wasn’t affected by the quake itself and was away from the concentration of aid work. But it’s a massive extra challenge added to a humanitarian crisis that was already overwhelming.

The terrifying reality is that however well aid agencies, the UN, and the Haitian government work to manage to isolate and contain the identified cases, it’s a real possibility that cholera will find its way to the stagnant pools and rubbish-strewn camps of Haiti’s capital.

Port au Prince is a prime cholera breeding ground. And children are the most vulnerable. In the last few days in the camps I’ve seen small children crouching by murky rivulets of water to rinse their hands. I’ve been chatting to mums as their babies reach for my hair, my necklace, my pencil, and try to drag them into their mouths.

There’s a huge prevention job to be done here, to teach parents how to protect themselves and their children from infection. As Dr Joseph, the Save the Children doctor in charge of the cholera response in Leogane (the earthquake epicenter) says, “the outbreak of cholera, for aid workers, is a declaration of ‘war.’”

And the fight is underway. Our teams are out in the communities working with thousands of people spreading the message of clean water; teaching families how to wash their hands properly with soap, to eat only well-cooked vegetables, explaining to young mums how feeding only breast milk to babies will help protect them from infection. We’re stocking our clinics with more drugs and supporting cholera treatment centres where new cases can be treated away from the rest of the community.

The hope is that none of these extra supplies will be needed. But it only takes one person carrying the bacteria to reach the stagnant pools of Port au Prince; one storm to flood the camps with the disease. A country where water itself has become the enemy is a frightening place to be.

Sarah Jacobs is the head of news at Save the Children

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