An emerging infection is defined as an infection that has newly appeared in a population while a re-emerging infection would be one that has existed in the past but its incidence has increased in recent times. The reasons for the emergence or reemergence of an infection are not completely understood but they are multifactorial and complex in the nature of their interactions. These factors may be related to the etiological organism, the host or the environment. Human activity appears to be a major driver. Malaysia had to deal with outbreaks of several emerging infections over the last two decades. They include Nipah virus infection, SARS and avian influenza. Infections like dengue, tuberculosis and leptospirosis are re-emerging in Malaysia. Both human activity and climatic changes appear to be key factors in the emergence and reemergence of infections in Malaysia. Our country needs to put in place a comprehensive plan to meet the challenge of emerging diseases. A multidisciplinary approach is required and the strategies involved should not merely confined to medical and health strategies.