A section of the South Shore Regional Hospital has re-opened to visitors. The health authority restricted visitation on the medical and surgical unit last week because of a stomach virus circulating among patients and staff. Lab tests have confirmed the illness as Norovirus, a common cause of gastroenteritis. Norovirus illness usually begins suddenly and can last up to three days. South Shore Health is reminding the public that regular and thorough hand washing can help prevent the spread of the illness.