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77 Cards in this Set
- Front
- Back
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What characterizes a zoonotic virus?
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Transmitted from animals to humans.
Reservoirs in lower vertebrates and may transmitted through vectors like blood sucking arthropods |
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What are the three groups of zoonotic viruses?
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Arboviruses
Roboviruses Other (rhabdovirus, pox via direct contact; filovirus unknown) |
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What do all arbovirus genomes have in common?
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All are RNA viruses that replicate in the cytoplasm.
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What are some vectors that maintain the cyclic transmission of arboviruses?
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mosquitoes, ticks, biting flies
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What are the arthropod-born virus families?
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Togaviridae (alphavirus)
Flaviviridae Bunyaviridae (some genera) Reoviridae Filoviridae |
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What human diseases are caused by Arboviruses?
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1. Asymptomatic, sub-clinical or mild disease
2. Encephalitis 3. Aseptic viral meningitis 4. Hemorrhagic fevers |
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What clinical diseases are caused by alphaviruses?
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Eastern equine encephalitis
Western equine encephalitis Venezuelan equine encephalitis Chickungunya |
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What is the morphology of alphavirus?
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small - enveloped - ss+RNA
2 glycoproteins Broad host range |
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What is the vector for alphaviruses?
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Mosquito
-Culex, Aedes, Culisetta |
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What is the host for EEE and WEE?
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Birds
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What is the host for VEE?
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rhodents, horses
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What is the difference clinically between EEE and WEE?
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EEE is a more severe illness, affects children and adults and can have severe neurological sequelae in half of survivors.
WEE is seen more frequently, is less severe --> complete recovery and mainly affects infants and children. |
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Where is EEE and WEE found?
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WEE = rural western US
EEE = rural US, NE down to Florida, Great Lakes, central and south america |
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Where is VEE found?
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Central and south america.
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What is the clinical manifestation of VEE?
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Infects mainly horses.
Mild systemic disease that rarely causes severe encephalitis. |
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What is the hosts for Chikungunya?
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Humans and monkeys
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What are the clinical manifestations of Chikungunya?
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"that which bends up"
Acute febrile illness with severe muscle pain and severe joint pain Rarely fatal. |
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What is the morphology of Flavivirus?
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small - enveloped - ss+RNA
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Which flaviviruses cause encephalitis?
Which cause systemic illness? |
encephalitis = SLE and West nile virus
Systemic = Dengue, Yellow Fever |
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Which flavivirus family members are not arboviruses?
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Hep C and Hep G viruses
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What are the host and vector for SLE and West Nile?
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Birds and mosquitoes
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What are the host and vectors for dengue and yellow fever?
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Primates and mosquitoes
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Describe flavivirus pathogenesis.
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1 - Prodrome, viremia
2 - Mild systemic disease 3 - Ab block, viremia 4 - encephalitis, hepatitis (yellow fever), or hemorrhagic fever |
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Describe transmission of SLE. (urban and sylvatic cycles)
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Sylvatic cycle: wild birds such as sparrows and mosquitoes
Urban cycle: mosquitoes infected from birds bite man (no man to man because not enough viremia) |
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Describe west nile virus history and hosts.
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An emerging virus first appeared in US in 1999. Transmitted by mosquitoes and wild birds to dead end hosts = horses and humans.
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Describe the pathogenesis and clinical manifestation of WNV.
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Asymptomatic in most humans.
In 20% --> sudden onset of fever, frontal headache, backpain, myalgias **Neuroinvasive = meningitis or encephalitis in 1/150. - Neuronal complications = flaccid paralysis, seizures, optic neuritis |
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What are some risk factors for WNV encephalitis?
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Over 50 yo.
Hypertension Immunosuppression |
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How is viral encephalitis diagnosed?
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Difficult to do based on clinical only.
Viral isolation in culture is difficult. Serology - detect IgM antibodies - acute phase, convalescent phase is 4-fold higher |
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What are types of illness does dengue virus cause?
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Classic dengue
Dengue hemorrhagic fever Dengue shock syndrome |
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Describe the transmission of dengue.
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1. Transmitted to humans via mosquito saliva.
2. Replicates in target organs. 3. Infects WBC and lymph tissues 4. Virus released and circulates in blood. |
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What is classic dengue?
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Mild systemic disease.
Targets skin, muscles and joints --> fever, malaise, m. and joint pain, rash on elbows, knees and chest spreads to extremities |
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What is hemorrhagic dengue?
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**Look up.
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Where is yellow fever endemic?
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Africa and South America
(first discovered arthropod borne virus!) |
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What are the transmission cycles for yellow fever?
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Jungle cycle: mosquitoes and monkeys (transovarial spread between mosquitoes)
Urban: mosquitoes to humans |
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What is the clinical presentation of yellow fever?
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Target organs = skin, kidneys, liver
Jaundice, fever, myalgias, proteinuria (kidney), hemorrhage of stomach mucosa = black vomit Mortality = 50% (no sequelae) |
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HOw is dengue and yellow fever diagnosed?
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Clinical presentation and SEROLOGY.
- isolate virus from blood or liver biopsy for yellow fever |
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How is dengue and yellow fever treated?
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No specific treatment - supportive.
*Yellow fever vaccine available for travelers to endemic areas. |
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What is the cause of Colorado tick fever?
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Coltivirus from the family Reoviridae
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What is the morphology of coltivirus?
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naked - dsRNA - double capsid
(Reovirus!) |
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Where does coltivirus replicate?
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Replication occurs in the cytoplasm of insect and mammalian cells.
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What are the clinical manifestations of colorado tick fever?
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mild or subclinical disease.
Resembles dengue: fever, chills, myalgia, lethargy. Can be more severe in children Usually no rash but if present differentiate from RMSF. |
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Describe transmission of colorado tick fever.
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Vector = tick; Reservoirs = squirrels and chipmunks
Common in hikers and campers; prevalent in CO, OR, UT, MT, WY |
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Name the Bunyaviridae family arboviruses and roboviruses.
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Arbo - California encephalitis, La Crosse encephalitis
Robo - Hantavirus |
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What is the morphology of bunyaviridae and what is unique about their matrix protein?
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ss (-) RNA - enveloped
Have NO matrix protein unlike other negative sense RNA viruses! |
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What is the clinical presentation of California encephalitis?
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Abrupt syndrome with fever
Highest attack rate for 5-18 yo Abrupt onset of encephalitis with seizures in 50% Lasts days and good prognosis with rare mortality |
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What is the California encephalitis complex?
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14 related virus members of Bunya family
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What is La Crosse encephalitis?
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Bunyavirus part of Cali complex.
Important in US. |
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What are the clinical manifestations of La Crosse E?
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Encephalitis leading to seizures
- majority of infections are mild or subclinical - neurologic sequelae resolve in 1 yr - clinically affects children under 16 - risk = living/playing in woodland areas |
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What are the host and vectors for california encephalitis and La crosse?
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Squirrel, chipmunk and mosquito
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What are virus families include roboviruses?
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Bunyaviridae
Arenaviridae |
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How do humans aquire infection from roboviruses?
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Inhalation of viral particles in contaminated rhodent urine or feces.
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What genus of Bunyaviridae is a robovirus?
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Hantavirus
(-ssRNA) |
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What are some clinical manifestations of hantavirus?
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Hemorrhagic fever with renal failure
Adult Respiratory Distress Syndrome (ARDS) Hantaan virus and Sin nombre virus |
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What is Hantavirus pulmonary syndrome?
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Similar prodrome febrile phase to ARDS but damage to capillaries occurs predominantly in the lungs, rather than the kidney.
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How is hantavirus diagnosed?
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serology: direct Ag detection
PCR Can isolate virus from urine early in infection |
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How do you treat infection with hantavirus?
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Supportive
Ribavirin if given early Vaccine tests in China; need rodent control |
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What is the morphology of Arenaviridae?
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ambisense ssRNA - 2 circular segments and a transcriptase - enveloped spherical or polymorphic
"arena" means sand --> host cell ribosomes often seen inside outer mem = sandy appearance |
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Name viruses part of arenaviridae.
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LCM virus
Lassa virus Junin virus Machupo virus |
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What are the animal reservoirs for arenaviruses: LCM, Lassa, Junin and Machupo?
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LCM: mus musculus (house mice)
Lassa: African bush rat Junin: Calomys mice Machupo: bush mice |
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What is the outcome of infection with arenavirus?
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Death or chronic lifelong viremia
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What is the clinical presentation of LCM?
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subacute choriomeningitis
nonspecific illness: fever, myalgia, vomiting, stiff neck, altered mental status illness may persist for 3 months |
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How is diagnosis of LCM made?
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Suggested by contact history.
CSF shows many lymphocytes |
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What does Lassa virus cause?
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Lassa hemorrhagic fever
- endemic in W. Africa, Nigeria - human to human transfer may occur |
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What are the clinical manifestations of Lassa?
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Insidious onset of non-specific symptoms: fever, petechiae, malaise, sore throat, diarrhea, acute deafness
Hemorrhagic --> liver and spleen necrosis, shock, coagulopathy Mortality rate 10-50%; higher in pregnant women; no damage to CNS |
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How is Lassa fever diagnosed?
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Recent travel to endemic areas
Serology: IgM detection by EIA --> virus can be isolated from blood, urine, throat but is a safety hazard; must isolate the patient |
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How do you treat Lassa?
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Ribavirin has limited activity. Must be given early.
Hyperimmune serum No vaccine. Prevent by rodent control. |
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What is the morphology of the family filoviridae?
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-ssRNA - enveloped - filamentous, pleomorphic
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What diseases are caused by filoviridae?
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Marburg and Ebola hemorrhagic fever
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Where is Marburg and Ebola virus found?
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Central and East Africa
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What are the vectors and reservoirs for ebola and marburg?
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Unknown!
Person-to-person transmission is seen during outbreaks. |
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Where was Marburg virus first detected?
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Marburg, Germany 1967
- African green monkeys from Uganda - Other outbreaks in Zimbabwe, Kenya, and Angola |
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What species is Ebola found in?
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Fatal in all species of monkeys
Four distinctive strains: Zaire, Sudan, Ivory Coast and Reston |
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What is the pathogenesis of filoviruses?
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Highly effective replication
Extensive necrosis in liver, spleen, lymph nodes, and lungs Severe thrombocytopenia |
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What is the clinical presentation of filovirus hemorrhagic fever?
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Incubate 4-6 days.
Symptoms like Lassa but Marburg and Ebola more severe disease. Mortality extremely high - up to 90% high level of person to person spread in rural hospital setting! |
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How is filovirus diagnosed?
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Clinical.
Recent travel to endemic areas. Isolate virus in Vero cells (only in BSL 4 labs). Serology: IgM and IgG by IFA Ag by ELISA, PCR |
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How is filovirus infection treated?
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No specific therapy.
No vaccine. Maintain renal function, electrolyte balance, control hemorrhage and shock. Ab-containing serum. IFN. |
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How can you prevent/control filovirus?
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Quarantine infected patient.
Sacrifice infected animals. Level 4 care of samples and infected materials. |
