The virus is present in the feces of infected persons for a couple of days after symptoms resolve. For this reason, public health officials recommend that during an outbreak, affected persons remain home from school or work for 48 hours after symptoms resolve.
Norovirus is highly contagious, and infected persons have enormous numbers of the virus in their feces. It is spread readily from person to person, and alcohol hand gels do not kill the disease, so hand-washing with soap and water is extremely important.