Hong Kong is ready to tackle swine flu. It is almost inevitable that cases will be found here. The government's alert level is serious, but will be raised to the emergency phase when the first sufferer is detected or the World Health Organisation has determined that a global pandemic is under way. Authorities are doing their part; now it is up to all of us to ensure vigilance and personal hygiene. The WHO has raised its warning level to five on a one-to-six scale, indicating that the threat of a pandemic is imminent. Governments the world over are expected to have preparedness plans in place. Hong Kong has been a step ahead, having been at the ready since the weekend. Border checkpoints and hospitals have been on alert and a special committee has met regularly to monitor progress. Health secretary York Chow Yat-ngok has said we must not be complacent. Chief Executive Donald Tsang Yam-kuen has told us to be psychologically prepared. Their advice is sound - and well grounded in experience. Our past battles with bird flu and Sars have taught us lessons and given us knowledge. Borders can never be fully impervious to swine flu; what we have learned and know, coupled with being ever ready, mean that we are as prepared as can be for an outbreak. The real test, however, will come if the swine-flu virus is found in Hong Kong and starts to spread. That is when policies have to be implemented and adapted to meet changing circumstances. The same applies to the mainland. Plans have been put in place. The handling of passengers arriving in Shanghai yesterday on the first direct flight to China from Mexico since the alert was sounded last week gives cause for confidence; the process went smoothly. In the past, mainland authorities have lacked transparency where outbreaks of infectious diseases were concerned. The indications that the media will be free to report on swine flu are encouraging. As we learned during Sars, transparency is vitally important. WHO director-general Margaret Chan Fung Fu-chun, our health chief during Sars, has rightly pointed out that questions remain about swine flu. How severe a pandemic will be is unknown. A vaccine has yet to be developed. Why there have been scores of deaths and people falling seriously sick in Mexico, but elsewhere only one person has died and cases have been mild is perplexing. Flu of various types kills hundreds of thousands of people around the world each year. Unorthodox varieties that move between species, like bird and swine flu, are by far the deadliest and most worrying. That they can rapidly mutate and, given the right conditions, easily spread raises concern that they can cause a pandemic. We must not panic. There is no need to worsen the downturn by shutting down transport networks and global trade. Governments should do as ours has done: monitor arrivals, stockpile anti-flu drugs and face masks, get hospitals ready to take and isolate patients and prepare contingency plans for closing schools and other public places. We must now turn attention to cleanliness and getting our homes and offices ready for the possibility of a swine flu outbreak.