Another subject that has received renewed attention is the possibility of human modification or management of viral virulence by impacting transmission dynamics. This is important for the application of rapid public health measures in the event of the emergence of new strains of parasites, bacteria or viruses (Lipsitch and Moxon 1997) . We presume we can influence virulence by the application of changes in human habits or by the use of control factors such as vaccines -and there are numerous precedents of how public health measures have changed the population dynamics of microorganisms (e.g., there are now more cases of vaccine-induced polio or yellow fever in some countries). Efforts to understand the relationship between parasite adaptation to hosts, virulence and transmission have developed into a small industry in evolutionary biology (Bull and Dykhuizen 2003) . Although most discussion is still theoretical, the relationships between virulence and transmission have been weighed, presuming that there is an evolutionary trade-off for optimizing either factor within an organism (Ebert and Bull 2003) . That is, to increase its chances of transmission to another host, an organism will limit its replication or virulence in so far as to not kill its host. For example, highly virulent, zoonotic viruses such as Ebola and rabies are less transmissible than measles or common cold viruses, which rarely kill their human host. However, this is overly simplistic when it comes to the evolution of viruses that have multiple strains (multiple infections, with some cross-protection), where virulence involves immunopathology, or where there is another host or an amplifying vector involved in transmission (Day et al. 2007 ). Thus, the main goal for disease control is to understand how we can reduce virulence in a virus population without making its level of transmission higher. However, this seems a daunting task if we include the effects of evolution by individual versus group selection, bottlenecks and changes in fitness trade-offs. The concern here is whether we will shift DENV evolution and population dynamics by applying incomplete control strategies (e.g., nonsterilizing vaccination or vector transformation).