Princess Diana worked on charities that focused on serious illnesses and health-related matters outside the purview of traditional royal involvement, including AIDS and leprosy. In addition, she was the patroness of charities and organizations working with the homeless, youth, drug addicts, and the elderly. Elton John pays tribute to Princess Diana. In August of 1997, just days before her death, Princess Diana visited Bosnia with the Landmine Survivors Network. Her interest in landmines focused on the injuries they created, often to children, long after a conflict was over. She is believed to have influenced the signing, though only after her death, of the Ottawa Treaty, which created an international ban on using anti-personnel landmines.