The winter vomiting bug norovirus has struck 2.8million people, with health professionals braced for another rise as people return to schools and offices. The virus - which causes projectile vomiting, diarrhoea, mild fevers and headaches - is striking down more than 200,000 a week, according to official estimates. Three hospitals have been placed on red alert, while hundreds of wards up and down the country have been closed to new patients as the number of beds being taken up by bug victims reaches critical levels.