The initial sense of urgency and alarm triggered by the arrival of swine flu in Hong Kong has eased as the weeks have passed. The virus continues to spread quickly in the community, but it is no longer regarded as a deadly threat to all who catch it. If the virus turns out not to be as dangerous as had been feared in the early days of the outbreak, the world will be able to breathe a sigh of relief. But governments must not drop their guard. Lessons must be learned from the reaction to swine flu and preparations put in place so that the world is ready the next time a dangerous infectious disease strikes. Our officials continue to modify their approach. While schools have closed, or are closing, early for the holidays to slow the spread of infection, the government has let them decide whether to go ahead with summer activities such as tutorials and special classes. Barring an unexpected turn of events, they will reopen as normal for the new school year. Influenza A(H1N1) is now being treated more like a seasonal flu, posing a serious risk only to the very young and old, the chronically ill and those with compromised immune systems. This contrasts sharply with the tough measures adopted as the city reported its first case, following reports of a growing number of deaths in Mexico, where the pandemic began. Wherever else it has appeared, the virus has proved relatively mild. Other places were more resigned to its spread and adopted less stringent countermeasures to slow it. This, once again, raises the question of whether Hong Kong overreacted. But our officials were right not to take any risks until more was known about the virus, especially given our experience with Sars in 2003. In fact, they can argue that they planned well in advance for the way things have turned out. Government sources said six weeks ago the response would be toned down if H1N1 continued to behave like seasonal flu. Containment measures were needed. But the ease with which the virus spreads meant they were bound to fail eventually. They have been replaced by more targeted mitigation measures. The city will soon have 500 swine flu cases, with scores more being reported each day. Without implementation of the emergency response plan, we might have reached that point much sooner. More importantly, a response plan based on lessons learned during Sars, and dusted off periodically during bird flu scares, has now been tried and tested against what seemed for a time to be a more serious threat. The experience should not be discounted. After all, it is not a matter of whether - but rather, when - we may have to rely on it again, only this time to save lives.