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172 People laugh when I say it but I really do love viruses. They fascinate me. The contrast between their structural simplicity and the complex interactions they have with the cells they infect as well as the sometimes drastic consequences on the infected host will never cease to amaze me. I am not noted for being a patient personso the fact that viruses evolve quickly also suits me.We can track and observe how they adapt to their environment in real- time. And there is such diversity among viruses that I dont have to worry about running out of things to learn. My research focuses mainly on viruses that are associated with emerging infectious diseases EIDs.An EID is an infectious disease that has newly appeared in a population or that may have previously existed but is rapidly increasing in incidence or geographic range.Well-known and topical examples include HIV- AIDS dengue chikungunya fever ebola virus disease avian and H1N1 influenza. About 75 of recent EIDs in humans and 60 of all human pathogens are diseases of animal origin.Im particularly interested in the mechanisms by which these viruses gain the ability to affect human populations and in some cases go on to have a major impact. We know that emergence requires that the causative agent is introduced into a vulnerable human population has the ability to spread from person-to-person and can be maintained in the population so that new infections continue to occur. In some cases this is achieved via genetic changes in the pathogen that increase its transmissibility host range and virulencebut very often it is a direct consequence of environmen- taldemographic and societal changes e.g.urbanisationalteration of natural habitats and rapid global travel that increase the probability of susceptible individuals coming into contact with infected hosts or vectors. My research groups current focus is vector-borne viruses such as the dengue viruses Chikungunya virus and other mosquito- borne viruses as well as rabies and other viruses carried by bats.We are trying to answer questions such as - What evolutionary and ecological factors determine viral emergence - What are the patterns of geographic spread demonstrated by emerging viruses in the Americas and what factors influence these patterns - How and where are viruses maintained between epidemics Is there regular reintroduction from other geographic regions or are they maintained locally at low levels - What are the animal reservoirs for current emerging viral diseases - What is the level of viral diversity in animal species that are likely sources of emerging viruses e.g. mosquitoes blood- sucking arthropods and bats Our general approach involves sampling viruses from the infected hosts or vectors sequencing their genomes and using state-of-the-art phylogenetic and bioinformatic techniques to estimate evolutionary relationships among viruses the rates at which they evolve and the forces driving their evolution the dates when individual viruses or specific lineages of a given virus arose how viral population sizes or levels of genetic diversity have changed over time their patterns of geographic spread spatial diffusion and to identify factors that determine and thus might be used to predict patterns of epidemic growth and spread. The beauty of this approach is that it relies on historical information contained in viral genomic sequences rather than epidemiological records to illuminate viral epidemic history.It can therefore recover information on virus transmission that occurred before systematic epidemiological surveillance was initiated.This is a very important consideration in developing countries given the deficiencies of public health infrastructure that frustrate the collec- tion of accurate and timely data through traditional surveillance mechanisms. To date we have completed investigations on the evolution and spread of dengue virus yellow fever and rabies viruses in the Americas. We have also characterised several viruses isolated during our extensive mosquito surveillance in forested regions of Trinidad some of which were previously unknown. This mosquito surveillance work provided updated information on viruses in circulation in Trinidad and their mosquito vectors. We are now focusing on dengue chikungunya and other viruses associated with febrile illnesses in patients presenting at selected healthcare institutions in Trinidad. In addition to providing greater insight into the evolution of these virusesthe level of viral diversity that exists in our region and the factors that shape this diversityour work results in estimates of how quickly specific virus populations are growingreconstruction of virus migration histories and identification of epidemiologically linked countries. In the case of dengue viruses we noted a high degree of virus movement within the Caribbean region and found that the intensity of viral traffic between countries was related to strength of economic and cultural ties between these countries. There was greater movement of virus amongst Caribbean Community CARICOM member countries than between CARICOM members and non-members. Our more recent MEDICAL SCIENCES Professor of Molecular Genetics and Virology Department of Pre-Clinical Sciences Tel 868 645 2640 ext. 4634 E-mail PROF. CHRISTINE V. F. CARRINGTON