MEDFORD - A Norwalk-like virus has surfaced in two Jackson County retirement communities.

About 25 residents at Mountain View Retirement Center in Ashland have been troubled by the nausea and violent diarrhea that are commonly associated with the Norwalk virus or close relatives known as "noroviruses."

The outbreak has also spread to the Rogue Valley Manor in Medford.

Several Jackson County retirement communities have reported outbreaks of gastrointestinal virus within the past year. Residents of an Eagle Point assisted living community fell ill in November, and more than 100 residents and employees of two Medford nursing homes were sick in January 2003.

Officials at both Mountain View and Rogue Valley Manor have been sanitizing buildings nightly to halt the outbreak. Residents who felt ill were asked to remain in their rooms and workers who attend them have worn gowns and masks to protect themselves.

The noroviruses are named after the Norwalk virus, which was identified as the source of an outbreak of gastroenteritis in Norwalk, Ohio, in 1972. They are also known as "cruise ship viruses" because they sometimes appear on those vessels, infecting large numbers of passengers and crew.