The influenza season has hit Hong Kong later than usual this year, with a large rise in the number of people in homes for the elderly and kindergartens suffering flu this month. Thomas Tsang Ho-fai, a consultant at the Department of Health's Centre of Health Protection, said the peak season for the virus was usually February, but 'we have detected a significant rise in influenza reports during May'. He said the department monitored private doctors treating flu patients, as well as influenza reported in homes for the elderly, childcare centres and kindergartens. All have seen an increase in the number of flu cases, and Dr Tsang expects them to continue to rise over the next two weeks. In elderly care homes, almost three in 1,000 residents reported flu symptoms this week, he said, while almost 10 per cent of all cases seen by general practitioners in the past week have been flu-related. Dr Tsang said the situation was similar to the influenza outbreak of 2001, when the flu season also began and peaked in May but continued to have high rates of infection throughout June and July. He was unable to explain why the influenza season had started so late this year. 'Influenza is a mysterious disease. The rise in cases in May is a little bit unusual, taking into account what we have seen in previous years,' Dr Tsang said. He said the circulation of three different strains of influenza during March may have prompted this month's outbreak.