Changes planned after Las Vegas marathon illness probe

On Dec. 4, 2011, some 44,000 runners participated in the annual Rock ‘n’ Roll marathon in Las Vegas. About 500 got sick with sapovirus.

A health district investigation determined that people were probably exposed to the virus the morning before the race — maybe at a runners’ expo where race numbers were distributed, although water distribution during the race had been suspected.

This year, organizers are promising several changes, including strict sanitation rules and a contractor supplying water to runners.