South Sudan’s hopes of officially being declared free of Guinea worm have been dashed after an outbreak of the parasitic disease was detected in the centre of the country.

Three people in the town of Rumbek have been diagnosed with the disease, the first cases in South Sudan for more than 18 months.

Guinea worm – classed as a neglected tropical disease – is not fatal but it is incredibly debilitating. Once the minuscule parasite is ingested, through drinking contaminated water, it can grow to three feet in size, causing immense pain.

It eventually emerges, usually through a leg or foot, after a year, a painful process that can keep victims bedridden for three months. Seeking relief from the pain, the victim often places his or her leg in water, causing the worm to release larvae, starting the cycle afresh.