Emerging and re-emerging infections

An emerging infection is defined as an infection which has newly appeared in a population while a re-emerging infection is one which has existed in the past but its incidence is rapidly increasing. The reasons for the emergence and re-emergence of infections are not well understood but appear to be associated with factors that involve the pathogen, the host and the environment. These factors are often inter-related and act together in a complex manner to bring about changes in patterns of infection. Pathogens are extremely resourceful and possess mechanisms to adapt to new hosts and environments as well as to acquire new virulence traits. Host factors include herd immunity, social behaviour and demographics. Environmental factors like the climate, deforestation and new technologies have an impact on the emergence of infections. The challenge is to contain an infection when it emerges but more importantly to prevent its emergence in the first place. As the emergence of an infection is complex and multifactorial, a multidisciplinary approach is required. Health based strategies alone are insufficient. Social, economic and environmental measures and the political will to implement appropriate policies are equally important.