The mood of caution and alertness that Hong Kong experienced during the 2003 Sars outbreak has apparently returned as the city gears up to guard against the outbreak of deadly swine flu. The government raised its influenza warning from 'alert' to 'serious', stepping up controls at the airport on Sunday. The government and private companies announced a string of hygiene measures yesterday to prevent another massive, deadly outbreak. The Education Bureau will send letters to all schools explaining the symptoms of swine flu. The bureau reminded schools to report any suspected outbreak of respiratory illnesses, to record the body temperatures of pupils and to step up hygiene measures in schools. A spokeswoman for the Leisure and Cultural Services Department said it would place disinfection carpets at the entrances of its buildings, while bleach solution would be used to disinfect escalator handrails, door handles, lift buttons and toilets. A spokeswoman for the Housing Department said it would continue routine cleaning measures in public housing estates, and would introduce more measures if necessary. The Link, which runs 180 shopping centres, car parks and wet markets, will post notices to raise public awareness of the outbreak and improve cleaning in wet markets. The MTR Corp will clean its train carriages with bleach solution every day, instead of once in three days. Escalators, ticket-issuing machines, entry and exit gates and lifts will be cleaned every four hours. MTR staff members are required to check their body temperature before work. MTR Corporation spokeswoman Miranda Leung Chan Chi-ming said its staff would be required to wear face masks if necessary. Kowloon Motor Bus is to continue its practice of cleaning the interior of its buses every day and washing the filters of bus air conditioners every week. It will also make more face masks available to drivers. Amoy Gardens - ravaged by the severe acute respiratory syndrome outbreak and evacuated in April 2003 - has resumed hygiene measures it initiated during that outbreak. Wilson Yip Hing-kwok, chairman of the Amoy Gardens Owners Joint Committee, said sterilisers had been installed in the lobby of each building and more than 20,000 face masks had been made available to residents. Disneyland is providing masks for its staff and visitors. A spokesman said accounting firm PricewaterhouseCoopers would maintain its stock of face masks and require catering staff to wear them, and public areas at its offices would be sanitised every two hours. Depending on how the flu outbreak develops, organisers of next week's Hofex hospitality trade show are prepared to screen the body temperatures of overseas buyers. HSBC has also taken some precautionary measures, while Cathay Pacific Airways is broadcasting a health advisory on all its flights arriving in Hong Kong.