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evolutionary medicine • diseases tracking hosts, and jumping to new hosts • virulence evolves • resistance evolves • antibiotics and evolutionary responses openclipart.org Cytomegalovirus pathogens tend to track hosts • Hosts are ENVIRONMENTS • immune response, nutrients, habitat density, physiological limits • Some pathogens are specialists on narrow range of hosts, others are generalist, broader niche Habitat shift is Often to a similar Environment (Related species) But not always similar! SARS virus apparently Jumped from bats To civets To humans 2003-04 Coinfection 2002-03 • Hemagglutinin evolution in flu virus can evolve through mutation as well as horizontal gene transfer from other virus when in same host • Required new vaccine to be developed Avian strain evolved Virulence In dense aggregations Human strain evolved With human Environmental background Bats also A common Source Human strain evolved With human Environmental background 2013: new outbreak of SARS - like virus In Middle East, appears again to originate in bats Again, we figure this out using PHYLOGENETICS Virus artificial selection = vaccine Variation (high mutation rate, large population size) May be heritable Differential survival Ones that survive carry genes that increased fitness How vaccine is developed using adaptation as a tool Green Goo Awful Orange Give one to UP TO 2 People YOU CAN REACH without standing Give one to Next nearest person (However far) Discuss • what element of pathogen biology did we simulate? • what happened to each pathogen? • what were the parameters in our model? • what would you change? What happens when a dense population with different demographics and migration patterns... Meets a sparse population that is naïve to the pathogen? Virulence Virulence associated w growth rate: uses host resource, by-product is disease Larger number people one interacts with Why selection affects virulence? 1. Population dies out if uses up resources before it finds more (general, selection is at level of host population) 2. Less quick-growing strain loses reproductive advantage to faster (more virulent) strain, selection is within host 3. Note selection (evolution) and competition (ecology) are analogous ways to discuss differential performance of diversity Lateral gene transfer • Diversity effect of sexual recombination, across diverse microbial taxa • SUPERBUGS • Strategy to cycle different antimicrobials in facility - helps population resistant to one antibiotic now be exposed to a second (can evolve) • Instead different treatment for each patient appears to have theoretical/model advantage Bergstrom's work suggests using multiple drugs in random design is probably best for limiting bacterial evolution • Not just in humans, HUGE usage in animals leads to resistant strains in livestock AND US no class thursday • Away at funeral • We will finish chapter 18 (aging and cancer among the topics) next Tuesday, stop there • Exam next Thursday 11/21