Common colds and related complications are a major healthcare burden in the US, with indirect and direct costs estimated at $60 billion a year, but now researchers have taken another step forward in the quest to cure the common cold - they have mapped the genetic codes of about 100 different cold viruses. By comparing the genomes of the various strains with one another, scientists were able to assemble a "family tree" of sorts and learn how the different strains are related. The researchers have determined that the various strains of rhinovirus(ライノウイルス)fall into 15 distinct categories, but further study is still needed before effective cold treatments can be developed.