Viral Pathogens (Final)Viral Disease – CharacteristicsAre nonliving organismsViruses effect every type of living organismbacteria, protozoa, fungi, plants, animalsRange of DiseaseBenign(harmless) extremely malignant(very harmful)Also everything in between/ wide rangeExample of being benign: warts on humansNo definitive treatment for any viral diseasehard to find selectively toxic drugPreventionEducation- knowing how certain diseases are transmittedQuarantine- to take people who are ill and separate them from the rest of the healthy population/ cutting down on direct transmission routesVaccination- most effective way to control viral diseaseNo more cases of polio due to huge vaccination programViral Disease - ControlViral Disease Currently Controlled through Vaccination and Preventionsmallpox - eradicated world-wide, vaccinationU.S. childhood vaccinationpoliomyelitismumpsmeaslesrubellaviral encephalitis - U.S. vector controlViral PathogensInfluenzaHIV (Human Immunodeficiency virus)Hepatitis virusesInfluenza (pathogen)An acute respiratory disease of warm blooded vertebratesReservoir – primarily wild birdsOften avirulent in reservoirHostsDomestic birds – ducks, chickensSwineHumansInfluenza VirusEnveloped RNA virus (- sense)RNA in 8 segments (codes for 11 proteins)two important envelope proteinsneuraminidase - helps virus penetrate mucus layer overlaying host cellshemagglutinin - used in adherence and penetration of host cellthree major types: A(more variations), B, Ceach major type has many variationsbased on variations of: (different proteins/ molecules)NeuraminidaseHemagglutininWhat makes Influenza potentially dangerous?Can infect several speciesVirulence usually different among speciesVirus can change readily (genetic material)How?mutation (antigenic drift)recombination of RNA from other influenza strains (antigenic shift)Due to simultaneous infections of two different strains in same hostOutcome:Infect new speciesBecome more virulentInfluenzaHistorical Considerationsrepeated epidemic(one location) and pandemics(worldwide incidence of disease/ multiple countries/ continents) throughout recorded historyOne of the worst pandemics(worldwide)Spanish Flu of 191820 million deaths worldwide500,000 Americans died within first 10 monthsnew types of the virus will certainly cause epidemics in the future. Pandemics?InfluenzaDiseaseinfection of the lower respiratory tract (lungs)rapid onsethigh feverfatigue, muscle acheschest congestion, coughingmay have cold-like symptomsmoderate to severe symptoms lasting 1-3 weeksInfluenzaComplications- serious ones from people who have lung problemssecondary bacterial pneumoniaoften fatal in young, elderly, and immunocompromisedtransmissiondroplet or aerosolcrowded conditionsmost cases seen winter and early springInfluenzaTreatmentsymptomaticantiviral prescription drug currently available“Relenza”, “Tamiflu”limits symptoms and duration of diseasePreventionVaccine availablenot always effectivea “cocktail” (mixed) vaccine against several types - each year a new vaccine must be producedHuman Immunodeficiency Virus (HIV) (pathogen)Cause of Acquired Immunodeficiency Syndrome – AIDS(bacteria)Human Immunodeficiency VirusStructureEnveloped RNA virusFamily: Retroviridaeother “retroviruses” cause malignant disease and have been identified for many mammals and birdscancerimmunodeficiency diseasereversetranscriptase - converts viral RNA into DNATwo variation of the virusHIV-1 and HIV-2Origins of HIVHIV-1 considered a “new” virusevolved (mutated) from existing virus ~1950s or earlierdisease unknown before 1980Early 1980’s first casesevolved from the simian immunodeficiency virusEarliest patientshomosexual menIV drug userslater persons receiving blood transfusions showing same diseaseThe Epidemicmorbidity35 million infected worldwide (2007, WHO, CDC)2/3 live in sub-saharan Africa1 million persons in USA infected (CDC)5 million new cases/year world wideMortality20,000 deaths/year in USA20 million deaths cumulative worldwide since 1981 (UNAIDS)TransmissionVirus found in body fluidsTransmissible levels in:semen, blood, vaginal secretionsModes of transmission:sexual contact with infected personIV drug use with needle sharingpassage from infected mother to infantreceipt of blood transfusions, blood product, organs from an infected personNOT modes of transmission:casual contact, mosquitoPathogenesisvirus infectslymphocytes, macrophages, dendritic cells, othersmain cell infected - T-helper lymphocyteTH cell count in the blood used to monitor progression of the infectionnormal count 800-1200< 200 patients considered to have AIDS or will develop AIDS within 1-2 yearsHIV adsorption to TH (CD4) CellsFigure 25.11Transmission & PathogenesisWhen too few TH cells exist patient unable to mount an adequate immune responsepatient succumbs to opportunistic pathogensStages of InfectionInitial infectionflu-like symptomsantibodies develop against virusLatent StageAsymptomatic- no symptoms at all1-8+ yearsHIV Disease (HIV related symptoms)AIDSCourse of InfectionFigure 25.16HIV Disease & AIDSHIV Disease (AIDS-related Complex)weight losspersistent swollen lymph nodesrecurring feverblood abnormalities (anemia, leukopenia)some opportunistic infection - recoverableKaposi’s sarcoma possibleAIDSsevere repeated opportunistic infectionsDeath due to infectionOpportunistic Infections of AIDSProtozoaCryptosporidium, ToxoplasmaFungiCandida albicans, Pneumocystis cariniiBacteriaMycobacterium avium. Mycobacterium tuberculosisVirusesCytomegalovirus, herpes simplexPrevention & TreatmentPreventionTestingBoth screening and definitive testsEducationVaccine - under developmentTreatmentTreatment of opportunistic infectionssymptomaticpassive immunization (immunoglobulin)Antiviral DrugsCombination Therapy: Nitrogenous base analogs + protease inhibitorsHepatitis Viruses(pathogen)General CharacteristicsMany different types of viruses infect human liver cellsThree main types:HBV - HepadnaviridaeHAV - Picornaviridae (an enterovirus)HCV - TogaviridaeAll cause inflammation of the liver (hepatitis)Hepatitis VirusesGeneral Signs and symptoms of hepatitis:Jaundice- yellow pigmentmalaise & fatiguevomiting, diarrheaabdominal painfeverhepatomegaly- liver problemsHepatitis B Virus (HBV)Known as serum hepatitisenveloped DNA virus, circular partially double stranded genomenot able to grow in tissue culture but easily isolated from blood of patientsPathogenesisaverage incubation period 90