“We$can$look$forward$with$confidence$to$a$considerable$degree$of$freedom$from$infec7ous$diseases$at$a$7me$not$too$far$in$the$future.$Indeed$.$.$.$it$seems$reasonable$to$an7cipate$that$within$some$measurable$7me$.$.$.$all$the$major$infec7ons$will$have$disappeared” $$$$$$T.$Adian$Cockburn$1963%“We%can%close%the%book%on%infec4ous%disease”%%%U.S.%Surgeon%General%William%Steward%1969%In%the%mid%20th%century%there%was%considerable%op4mism%on%our%ability%to%combat%and%defeat%infec4ons%diseases.%%%%%Some%of%the%reasons%for%this%are:% %1]%vaccines%(yellow%fever,%% %%%%%%%%%%% % %%%%%%small%pox,%polio)%%%%%%%%%%2]%cloroquine%%%%%%%%%%3]%DDT%%%%%%Some%quotes%that%exemplify%this%aNtude:%%1"Emerging%and%ReQemerging%infec4ous%disease%%• %An%emerging%disease%is%one%that%has%appeared%in%a%%%%popula4on%for%the%first%4me,%or%that%may%have%%%%existed%previously%but%is%rapidly%increasing%in%%%%incidence%or%geographic%range%%%• %ReQemerging,%or%resurging,%diseases%are%those%that%%%%have%been%around%for%decades%or%centuries,%but%%%%have%come%back%in%a%different%form,%different%% %%%%%%%%%%%intensity,%or%a%different%loca4on%For%a%variety%of%reasons,%this%op4mism%was%misplaced%and%we%have%seen%the%%emer gence%or%reQemergence%of%many%new%infec4ous%diseases%since%then. %%These%new%diseases%are%classified%as%“Emerging%and%ReQemerging%infec4ous%diseases”%2"Dengue%impact%%• %2.5%billion%people%at%risk%• %50Q100%million%infec4ons%yearly%• %500,000%Dengue%Haemorrhagic%Fever%cases%• %22,000%deaths,%mostly%children%3""Mosquito%bite%Aedes$aegyp7$Incuba4on%3Q14%days%Febrile%Period%5Q7%days%Convalesence%3%weeks%%Dengue%Clinical%Syndromes%%%1]%50%%asymptoma4c%%%%%2]%%undifferen4ated%fever%(most%%%%%%common%manifesta4on)%%3]%%classic%dengue%fever%(feve r %%%%%%headache,%muscle%and%joint%pain%%%%%%pain,%nausea/vomi4ng,%%%% %rash)%%4]%dengue%heamorrhagicfev e r%(DHF)%%%%5]%dengue%shock%syndrome%(DSS)%4"Dengue"fever"Dengue""haemorrhagic""fever"5"Why%do%some%people%develop%DHF?%Several"ideas"were"proposed"to"explain"DHF:""• Various"forms"of"the"four"serotypes"cause"different"disease?"• Prior"exposure"to"other"serotypes"makes"disease"worse?G>""This"is"called"the"Immune"Enhancement"Hypothesis"• PopulaLon"increase"G>"more"people"so"higher"probibility"of"DHF""• Human"GeneLcs"G>"Some"people"are"more"suscepLble"than"others?"This%is%now%widely%excepted%%6"Dengue%virus%is%occassionally%transmiced%ver4cally%• Transovarial"transmission"of"virus"can"occur!• Ae!aegyp(!eggs"subjected"to"adverse"hatching"condiLons"can"remain"viable"in"the"environment">100"days"This"means"that"the"virus"can"hide"out""in"eggs"for"a"long"Lme""Virus"does"not"disappear"during"dry"or"cold"season"Transmission%from%female%to%offspring%7"ReQemergence%of%Dengue%Fever:%%%%Why?%• Unplanned%Urbaniza4on,%%%%%%%%%%(especially%in%tropics)%• Growing%popula4on%– More%urban%areas%large%%%%enough%to%sustain%ongoing%viral%circula4on%• Poor%housing%• Poor%vector%control%%%• Travel%and%migra4on%Presumed"reasons:"8"Increase In DHF Hyperendemicity: the occurrence of multiple serotypes in a locations 9"US-Mexico Border IgM"posiLve"=>"recent"exposure"IgG"posiLve"=>"exposure"at"some"Lme"in"the"past"Plenty"of"Dengue"on"US"side"G>"oYen"underdiagnosed"10"Global%Public%Health%Entomology%Mosquitoes%and%the%diseases%they%transmit:%Yellow"Fever"11"The"yellow"fever"mosquito"Human"vector"of"yellow"fever"(and"Dengue"fever)"Originated"in"Africa:"Spread"to"New"World"during"16th"century"through"slave"trade""""G>"urban,"human"feeding"form"Aedes!aegyp(!""""(there"is"also"a"sylvaLc"(forest)"breeding,"generalist"form)"""G>"breeds"in"stagnant"water,"e.g."flower"vases,"Lres,"""""""uncovered"water"storage,"wet"showers,"toilet"tanks""""G>""recently"replaced"in"the"US"by"Aedes!albopictus!""""Aedes!aegyp(!12"Viral"haemorrhagic"disease"(Flavivirus)""Mostly"found"in"primates"(including"humans)"and"is"transmieed"by"several"species""of"mosquito""Major"epidemics"in"the"17G19th"centuries,"(Including"numerous"outbreaks"in"the"US"""as"far"north"as"New"York)""Currently:""WHO"esLmates:"200,000"cases/year""""""30,000"fataliLes"(most"unreported)""""""90"%"in"Africa"""""""600"million"people"at"risk"Yellow"fever"13"1]"AsymptomaLc"Cases"Inapparant/apparent"raLo:""""1/2"in"naïve"children"prior"""""""""exposure"to"some"other"flaviGviruses"can"provide"some"""""""""""crossGimmunity"G>"22/1"raLo""2]"Mild"fever"cases"""""Fever"""""Nausea""""Headache""""Nose"bleeding""""Slow"heart"rate""""Yellow fever symptoms 3-6 days intrinsic incubation period ""This"typically"takes"""about"48"hours""14"Yellow"fever"symptoms"3]"More"Serious"Cases:""1st"phase""High"Fever" "Seizures"Headache " "Nausea"Dizziness " "VomiLng"Red"eyes " "Bloody"nose/gums""2nd"Toxic"Phase""Liver"damage"Jaundice"""Internal"bleeding":""Black"Vomit,"resembling"coffee"grounds"G>"invariably"fatal"15"Yellow"fever"cycle"Africa"Transmission"cycle"of"yellow"fever"in"Africa"Insert"graph"3.11"Yellow"fever"is"maintained"in"zoono4c%(primates)"jungle"cycle"(primates"do"not"die)""People"entering"the"jungle"can"bring"yellow"fever"into"rural"and/or"urban"cycle""Rural"cycle"takes"place"at"the"edge"of"forests"and"various"other"mosquitoes"are"involved.""Transmission"between"humans"by"Aedes!aegy("in!urban"(villages"and"towns)"cycle""""16"Yellow"fever"cycle"South"America"Transmission"cycle"of"yellow"fever"in"South"America"Yellow"fever"is"maintained"in"zoonoLc"(primates)"jungle"cycle"(primates""die)""People"entering"the"jungle"can"bring"yellow"fever"into"urban"cycle"(villages"and"ciLes)""No"intermediate"cycle"""Transmission"between"humans"by"Aedes!aegyp("in"!urban"cycle"Insert"graph"3.12"17"Yellow"Fever"DistribuLon"90%"of"cases"CDC"esLmates:"200,000"cases"yearly,"30,000"fataliLes"18"Yellow"fever"distribuLon"Aedes!aegyp(!distribuLon!Why"yellow"fever"has"never"made"it"to"Asia?"Possible"reasons:""G>"lower"vector"competence"of"Asian"Aedes!aegyp(?!!3>!Cross"protecLon"from"other"flaviGvirusses"(e.g.""Dengue)?!!19"Aedes$aegyp7$• Wide%distribu4on%in%urban%areas%– Well%adapted%to%contemporary%urban%life%%• Breeding%sites%– Discarded%plas4c%containers,%cans%– Used%4res,%flowerpots,%tree%holes%• Enters%homes;%prefers%human%blood%•