Nepal’s Floods Left Thousands Unidentified. DNA Can Help

The Bhotekoshi flood left families searching for loved ones among remains that water and debris had made almost impossible to recognise. More than 1,000 people died, at least 3,916 remained missing, and some bodies were swept downstream into India.

Nepal has turned to forensic DNA testing. The science rests on ordinary biology, but applying it in a disaster zone is difficult. Bodies recovered from floodwater may be swollen, discoloured and barely recognisable. Prolonged soaking can loosen skin from hands and feet, removing fingerprints. Currents may strip away clothing and documents, while rocks, debris and mud can destroy or conceal fractures, tattoos and scars.

As remains stay in warm, contaminated water, visual identification becomes less reliable. Forensic teams increasingly depend on teeth and dense bone, which can preserve DNA after skin and muscle have broken down. At Nepal Police’s Central Police Forensic Science Laboratory, technicians clean a tooth or bone fragment, drill or grind it into powder, remove its mineral structure, and use detergents and enzymes to release the DNA. They then purify and assess the sample before testing it.

Families provide cheek swabs or blood samples. The most useful comparisons usually come from parents, children or siblings, who share inherited genetic material. Laboratories do not need to sequence an entire genome. Instead, they examine short tandem repeats at multiple locations, copy those regions through multiplex PCR, and use fluorescent markers and capillary electrophoresis to produce a numerical genetic profile.

The process cannot reverse the flood or restore what families have lost. It can, however, help establish identities and give families the possibility of bringing their dead home.