Emerging viruses Lecture 22 Biology W3310/4310 Virology Spring 2015 Nothing endures but change HERACLITUS Emerging viruses • Emerging virus - causaFve agent of a new or previously unrecognized infecon • The terM became popular in 1990s, but eMerging viruses are not new • Since the rise of agriculture - 11,000 years ago - new infecFous agents have invaded huMan populaFons because they can be sustained by nuMbers that were unknown before agriculture and coMMerce Emerging viruses • Expanded host range with an increase in disease not previously obvious • TransMission of a virus froM a wild or doMesFcated aniMal to huMans - zoonosis • Cross-species infecFon May establish a new virus in the populaFon (SIV Moving froM chiMps to huMans) • OVen cross-species infecFon cannot be sustained (e.g. Ebola and Marburg froM bats to huMans) Human - animal interface 6 16 32 Adapted pathogens (> HoMo sapiens) ZoonoFc pathogens HeirlooM pathogens (< HoMo spp.) HeirlooM pathogens (> HoMo spp.) 37 Viruses belonging to # of genera One Health, ASM Press Convergent Forces of Disease Emergence GLOBALIZATION RAPID AIR TRAVEL ALTERED ECOSYSTEMS EXPANDING POPULATIONS “MEGA- CITIES” POVERTY MICROBIAL EVOLUTION DEFORESTATION ENVIRONMENTAL CHANGES Over-riding factors driving the emergence of infecLous diseases of humans and animals: Human popula8on growth and incredible change occurring in all ecosystems brought about by human occupa8on of almost every corner of the planet The Amazon North Region of Brazil Home to 183 Arthropod-borne and Other Vertebrate Viruses Cacipacore, Trombetas, Mapuera, Serra do Navio, Oriximina, Turuna, Saraca, Juruaca Araguari, Amapari, Aura, EEE, Una, WEE, Bussuquara, Ilheus, Ieri, Cupixi Kairi, Maguari, Taiassui, Caraparu, Itaqui, Munguba, Jari, Jutai, Murutucu, Nepuyo, Melao, Acara, Benevides, Monte Dourado, Paru, Benfica, Bushbush, Capim, Guajara, 0º Tumucumaque, Almeirim Ananindeua, Bimiti, Catu, Mirim, Moju, Timboteua, Utinga, Turlock, Bujaru, Icoaraci, Itaporanga, Urucuri, Belem, Para, Acado-like, Mosqueiro, Kwatta-like, Chaco, Timbo, Piry, Marco, Aruac, Inhangapi, Agua Preta, Cotia- like, Marajo, Mucambo, yellow fever, Tacaiuma, Tucunduba, Apeu, Marituba, Boa Vista Melgaco Oriboca, Caraparu-like, Guama, Anhanga, Mayaro dengue 1, dengue 4 dengue 2, dengue 3, Bocas, Triniti, Amapa Barcarena Roraima Macapa Pixuna, SLE, Lukuni, Sororoca, Guaroa, Belem Oropouche, Candiru, Pacui, Caninde, Gurupi, Irituia, Ourem, Tembe, Cocal, Jurona Balbina, Manaus Uatuma Para Arumateua, Caraipe,Tucurui,Guamboa-Like, Uriurana, Anapu, Aracai, Aratau, Aruana, Arawete, Bacuri, Canoal, Coari, Iopaka, Ipixaia, Iruana, Itaboca, Jandia, Jatuarana, Pacaja, Parakana, Murumbi Paranati, Pependana, Pindobai, Piratuba, Surumbi, Tekupeu, Timbozal, Tocantins, Tocaxa, Tuere, Xaraira, Xiwanga, Breu Branco, Trocara, Jatobal, Amazonas Jacunda. Itupiranga Palmas Porto Velho Iaco, Moriche, Acre Xingu, Ambe, Joa, Tapara, Purus, Sena Mojui dos Acatinga, Acurene, Altamira, Madureira, Campos, Santarem, Assurinis, Bacajai, Gorotire, Xiburema Rio Branco Belterra, Jamanxi Kararao, Uxituba, Cajazeira, Cuiaba, Tocantins Codajas, Galibi, Iriri, Uruara Rondonia Alenquer Ariquemes Atlantic Ocean Itaituba, Pacora- like, Jacareacanga, Flexal North Region South America Serra Norte, Catete, Parauapebas, Serra Sites froM which viruses were isolated at the Sul, Tapirope, Carajas, Maraba, Brazil Curianopolis, Evandro Chagas InsFtute Itacaiunas Atlantic Ocean 0 500 1,000 Kilometers Virus Family Drivers of Emergence Urban population density, Dengue virus Flaviviridae mosquito breeding Human contact with natural Ebolavirus Filoviridae host; bushmeat Agriculture: human/rodent Hantaan virus Bunyaviridae contact Bats to horses to stable Hendra virus Paramyxoviridae workers HIV Retroviridae Bushmeat trade Influenza virus Orthomyxoviridae Pig/bird agriculture Junin virus Arenaviridae Agriculture: human/rodent contact Nipah virus Paramyxoviridae Bats to pigs to humans Machupo virus Arenaviridae Agriculture: human/rodent contact Rift Valley virus Bunyaviridae Dams, irrigation Weather, human/rodent Sin Nombre virus Bunyaviridae contact West Nile virus Flaviviridae Mosquito Principles of Virology, ASM Press Roles of EvoluLon • Leads to the biodiversity of pathogens exisFng in nature (quasispecies) • AdaptaFon to new hosts and environMents (through variaFon and selecFon) The general interacons of hosts and viruses • Stable: Maintains virus in ecosysteM • Evolving: passage of virus to naive populaFon • Dead-end: one way to different species • Resistant host: infecFon blocked Principles of Virology, ASM Press Stable host-virus interacLons • Both parFcipants survive and MulFply • SoMe are effecFvely perManent - Humans are sole natural host for measles virus, herpes simplex virus, HCMV, smallpox • May include infecFon of More than one species - Influenza A virus, flaviviruses, togaviruses Principles of Virology, ASM Press Evolving host-virus relaLonshiP • HallMarks are instability and unpredictability • OutcoMe of infecFon May range froM benign to death - IntroducFon of sMallpox and Measles to naFves of AMericas by Old World colonists and slave traders - IntroducFon of West Nile virus into Western HeMisphere, 1999 • IntroducFon of rabbits into Australia Principles of Virology, ASM Press Dead-end interacon • Frequent outcoMe of cross-species infecFon • Ebolavirus: huMans, chiMps, gorillas • New infected host May not transMit the infecFon to others of the same species (H5N1) • Contribute ligle to the spread of a natural infecFon Principles of Virology, ASM Press The complex life cycle of an arbovirus Stable host- virus interacFons Principles of Virology, ASM Press Rodents and insect vectors move EuroPean ck-borne encephalis virus among many hosts Dead-end hosts Principles of Virology, ASM Press Other dead-end infecons • Yellow fever (Monkey) • Marburg, Ebola, Hendra, Nipah, SARS progenitor (bats) • Lassa, Junin, Sin NoMbre (rodents) • Laboratory aniMal Models Emerging infecLons: Two stePs • IntroducFon • EstablishMent and disseMinaFon Encountering new hosts • Rare chance encounters of viruses with new hosts may never be detected • Single-host infecFons are not transMiged among huMans for Many reasons Expanding viral niches • Successful encounters require access to suscepFble and perMissive cells • PopulaFon density and health are iMportant factors • Virus populaFons will endure in nature only because of serial infecons (a chain of transMission) Human are constantly providing new ways to meet viruses Dams and water iMpoundMents IrrigaFon Massive deforestaFon RerouFng of wildlife MigraFon pagerns Wildlife parks Long distance transport of livestock and birds Air travel Uncontrolled urbanizaFon Day care centers Hot tubs Air condiFoning Used Fre trade Blood transfusion XenotransplantaFon Sex and drug abuse Principles of Virology, ASM Press Diseases of exploraon and colonizaon • Explosive epideMic spread May occur when a virus enters a naive populaFon • SMallpox reached Europe froM the Far East in 710 AD, agained epideMic proporFons • SMallpox changed the balance of huMan populaFons in the New World - killed 3.5 Million Aztecs in 2 years (1520 - spread froM Hispaniola), allowing conquest by Cortez Yellow fever virus: Humans change the PaUern and pay the price Yellow fever deaths, Philadelphia, 1793 “Yellow Fever will discourage the growth of great ci8es in our na8on” THOMAS JEFFERSON, 1800 Principles of Virology, ASM Press Changes in human poPulaons and environments • EMergence of epideMic polioMyeliFs in the beginning of the 20th century: iMproved sanitaFon delayed transMission • Known since 4,000 years ago, stable host-virus relaFonship PoliomyeliLs: A disease of modern sanitaLon Principles of Virology, ASM Press Influenza 631 deaths | 253 deaths Bats: a source of zoonoc infecLons •Many new paramyxoviruses found in flying foxes since 1995, including Nipah and Hendra viruses •Cause severe disease in doMesFc aniMals (horses and pigs) and are known to infect huMans Nipah virus • First outbreak Malaysia 1998 - Outbreak of respiratory and neurological disease on pig farms - 105 human deaths, 1 million pigs culled • Fruit bats excrete virus in urine but are unaffected • Pig farMers plant Mangoes near pigpens • Pigs spread infecFon to huMans • Subsequently huMans infected by consuMing date palM sap contaminated by bats (India, Bengladesh) • HuMan to huMan transMission; infecFons conFnue Hendra virus • Discovered in Hendra, Australia, SepteMber 1994 - Outbreak killed 14 racehorses and a trainer • Spread froM flying foxes to horses, then to huMans • Horses conFnue to acquire infecFon hgp://www.twiv.tv/2014/08/03/twiv-296/ Changing climate and animal poPulaons • Hantavirus pulMonary syndroMe - first noted in Four Corners area of New Mexico, 1993 • Disease is caused by Sin NoMbre virus, endeMic in the deer mouse (Peromyscus maniculatus, 30% virus posive) • Originally called Muerto Canyon virus, but residents objected Changing climate and animal poPulaons • In 1992-93, abundant rainfall produced a large crop of piñon nuts, food for huMans and the deer Mouse. Mouse populaFon rose, contact with huMans increased. • Virus is excreted in mouse feces; contaminated blankets or dust froM floors provided opportuniFes for huMan infecFon • HuMans not the natural host for Sin NoMbre virus, huMan disease is rare • Not new - earliest known case 1959 Deer Mouse, white-footed Mouse, rice rat, cogon rat New World Hantaviruses New York Sin Nombre Peromyscus leucopus Peromyscus maniculatus Prospect Hill Muleshoe Microtus pennsylvanicus Sigmodon