Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain
the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in
Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles
Earlier this year, Deborah Ashom received news that many Nigerian mothers fear. Sean, her six-week-old son, had tested positive for sickle-cell disease. She knew this meant his future might hold bouts of anaemia, infections and painful crises resulting from his c-shaped red blood cells. It would probably also shorten his life — in Africa, up to 80% of children born with the disease die before they turn 5.