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Health 101 Topic 9 Infectious Diseases and the future of Human Health (abstract) 1/ CURRENT/EMERGING PLAGUES i. AIDS -approximately 33 million in world HIV positive 2007: 2 million die, 2.7 million infected -decline in deaths/new cases since 2

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Queen's University
Health Studies
HLTH 101
Glenn Ward

TOPIC 9. INFECTIOUS DISEASES AND THE FUTURE OF HUMAN HEALTH 1/ CURRENT/EMERGING PLAGUES i. AIDS -approximately 33 million in world HIV positive 2007: 2 million die, 2.7 million infected -decline in deaths/new cases since 2005 (not in all regions) - most cases/deaths in sub-Saharan Africa -greatest increase is in Eastern Europe/Central Asia -important characteristics: 1) no vectors/animal reservoir (HIV actually no from monkeys) 2) low infectiousness (need to exchange bodily fluids) 3) long latency (10-15 years to see symptoms, opportunity to transmit) 4) hedonistic transmission (feel good activites (sex, drugs) making it difficult to eliminate) 5) destroys helper T cells –seeks CD4 receptor, enter, and destroys cell -increases susceptibility to other infections -effects in developing world -implications on treatment: destroy host cells? Treatment: 1) reverse transcriptase inhibitors (prevent multiplication) ie. AZT (azidothymidina) -temporary effectiveness (virus may develop resistance) -nucleotide (act on DNA) and non-nucleotide inhibitors (act on enzyme) 2) protease inhibitors - reduce reassembly, temporary resistance 3) AIDS cocktails - Highly Active Anti-Retroviral Therapy (HAART) -combinations of antiviral drugs -resistance from mutation is less effective as different drugs can combat different mutations -combination of: -reverse transcriptase inhibitors -protease inhibitors -entry inhibitors (disallow CD4 receptor entry) -integrase inhibitors (blocks activation of integrase which injects virus injected DNA -effective reduction of symptoms, increase life expectancy -only temporary resistance (eventual development of resistance) -can also reduce mother-child transmission -when to start HAART: 1990’s: at start of AIDS symptoms Today: early at infection, before symptoms - reduces concentration of virus in body (viral load) - could reduce transmission as result (less virus in bodily fluids) -issues: -severe side effects -complicated treatment regime -expensive (more than $10 000/year) (not effective in developing countries) -increased resistance due to new strains; harder to develop vaccines -in future, hopefully more prevention emphasis, possibly new resistant strains ii. Influenza Viruses -RNA -3 types, based on internal antigens C: mild B: humans mostly, moderate severity A: potentially severe, pandemics, animals/humans -transmitted in aerosol, respiratory droplets -first 18-72 hours: cold symptoms, muscle pain, congestion, fever -can last 5-10 days -virus replicates in respiratory epithelial cells resulting in cell death -special features: capacity for antigenic change Viral coat: 2 glycoprotein antigens: 1) Hemglutinin (15 known subtypes: H1-H15) 2) Neuraminidase (9 known subtypes: N1-N9) -glycoprotein is same but it is the antigens that change -antigenic shift: genetic recombination from more than 1 strain (different host species) -ie. pig exposed to human and bird virus - same cell with both viruses -new virus with RNA from both viruses -then transmitted to human, no antibody protection due to new antigens -human influenza A pandemics: 1918: H1N1; 1956:H2N2; 1968: H3N2; 1977:H1N1; 2009: H1N1 -H and N not necessarily correlated with viruklence/infectiousness (ie. 1918, 1977, 2009: H1N1 reduced virulence each time) -emergency epidemic/pandemic: 1) H5N1: avian influenza -asia -high human case fatality rate (60%) -not easily transmitted (only from bird to human, so far) 2) H1N1: swine flue -easily transmittable -low case fatality rate (less than 10%) -prevention focus Vaccines: WHO (world health organization) coordinates response -identify likely viruses -prepare trivalent vaccine -problems: -after epidemic/pandemic begins, maybe too late to make vaccine -must predict viral antigens and amount required Treatment: Antivirals: -neuraminidase inhibitors (decrease spread in body; ie. Tamiflu) Problems: -supply, storage (shelf life, amount needed) -even after treatment, still infected -increased resistance iii/ Malaria -humanity’s worst health problem -2008: approximately 250 million cases -40% of human population is at risk -less than 1 million die (most less than 5) - in Africa, a child dies every 45 seconds from malaria -comes from plasmodium parasite: 4 main types: 1) P. Falciporum is most serious -life cycle: between mosquito and human -Anopheles female species -usually bite at night -parasite reproduction in liver and move to red blood cells -further reproduce in blood cells, then destroy and continue to reproduce in new red blood cells -results in haemolytic anemia (low iron, destroys haemoglobin (cannot deliver oxygen) -results in chills, fever patterns and if not recovered, can got into coma and die Eradication: -by 1950, public health success in North America, south America, Europe, parts of Asia (no malaria) -at risk population dropped by 50% by 1950 )done by destroying Anopheles habitat (standing water) -not a biomedical success (just eliminated mosquitos) -1950’s, WHO founded -solved by resources from outsiders, not locally -failed eradication in Africa and South Asia (worsened) - due to political instability in region (ie. Africa colonized by Europeans) 2000,2006: ―roll back Malaria program‖ -reduce deaths by 50% (2010) – already failed -reduce deaths by 75% (2015) – right now, not on target -approach: -insecticide-treated mosquito nets - drain standing water -medical treatment (help, not solve) -develop vaccine (still none) -in all, focus on AIDS hurt malaria
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