Ch32-33 Corona- picorna- arbo Flashcards
describe coronaviruses
- positive strand RNA viruses
- enveloped
what is the agent of COVID 19
SARS-CoV-2
what is MERS and what is the mortality rate
- middle east respiratory syndrome
- viral respiratory illness
- 30-40% mortality rate
what is the coronavirus life cycle
- 1st phase of translation: includes an RNA dependent RNA polymerase
- 2ns phase of translation
- acquire viral envelope by budding of nucleocapsid into the ER
what are the clinical presentations of people with SARS CoV 2
-asymptomatic
- mild illness
- moderate illness
- severe illness: less than 94% O2, PaO2/FiO2 less than 300 mmHg, less than 30 breaths per minute
- critical illness: respiratory failure, septic shock, multiple organ dysfunction
explain the viral entry mechanism of SARS coV 2
RBD of spike protein binds to ACE2
what does ACE2 do
lowers BP
what does TMPRSS2 do
transmembrane protease, serine 2 cleaves spike protein
what are the proposed mechanisms of COVID 19 infection
- direct cytotoxic effect
- dysregulatino of RAAS
- endothelial cell damage and thromboinflammation
- dysregulated immune response
describe picornaviruses
- positive stranded RNA viruses
- do not have envelope
what is the habitat of enteroviruses and what are they types
- GI tract
- poliovirus and coxsackievirus
what are the types of picornaviridae
- enterovirus
- hepatovirus
- parechovirus
- rhinovirus
what are the types of enteroviruses
- coxsackievirus A
- cocksackievirus B
- echovirus
- enterovirus
- poliovirus
what is the habitat for rhinoviruses
respiratory epithelium
describe enteroviruses
- very stable in food and water
- stable at pH3 (stomach)
describe rhinoviruses
- sensitive to acidic pH
- replicate poorly above 33 C
describe organ involvement for enteroviruses
- only occurs if viremia persists
what are the 3 types of polioviruses and what are the differences between the types
- PV1, PV2 and PV3
capsid differences
what is the transmission of poilioviruses
fecal-oral
what is the poliovirus receptor
CD155
what is the poliovirus IRES and what does it stand for
- internal ribosome entry site
- serves as the cap of the viral RNA, promoting translation of viral RNA into viral proteins
because of IRES where does translation start
far from the 5’ end of poliovirus RNA
how does poliovirus affect the CNS
- flaccid paralysis: destruction of anterior horn cells in spinal cord
- bulbar poliomyelitis: respiratory muscle paralysis
what are the factors that increase the severity of poliovirus infections
- physical exertion and trauma
- tonsilectomy
describe the poliovirus vaccine
live oral vaccine (Sabin) mimics the normal infection process of poliovirus
what does group A coxsackieviruses cause
-aseptic meningitis
- herpangina: sudden fever, vesicles on tonsils and palate
what does coxsackievirus type A16 cause
hand, foot and mouth disease
what does group B coxsackievirus cause
- heart (myocarditis)
- respiratory tract (pleurodynia)
- mucous membranes of eye ( hemorrhagic conjunctivitis)
what accounts for 50% of the common cold cases
rhinoviruses
what is the mechanism of action of rhinoviruses
binds to respiratory endothelial cells via ICAM-1 or VLDL receptor
describe rhinoviruses
acid sensitive
33 C optimum for replication
- no tissue destruction
what are the complications of infections of rhinoviruses
sinusitis, otis media
- worsening asthma
why are vaccine prospects poor for rhinoviruses
too many variants
what are arboviruses transmitted by and where do they multiply
- arthropods
- in tissues of vector, without producing disease
describe arbovirus infections in humans
- viremia of short duration
- virus levels in blood are low
what are the species that transmit arbovirus infection
- togaviridae
- flaviviridae
- eastern equine ecephalitis
- western equine encephalitis
- St. louis encephalitis
- west nile
- zika
descride togaviruses
- plus stranded RNA
- enveloped
describe togavirus infection
- 2 phases of translation
- first produce early proteins and then late proteins
- like coronavirus
describe rubella virus
- member of togavirus family but not arthropod borne
what does rubella cause
german measles
describe flaviviruses
-plus stranded RNA
- enveloped
what does zika virus cause
- mostly mild illness except congenital infection which leads to microcephaly
how is zika virus transmitted
mosquitos and sexually
what is dengue fever and what causes it
- most prevalent disease caused by arboviruses
- does not cause significant mortality
- caused by a flavivirus
- mosquitos
what happens upon reinfection of dengue fever
- dengue hemorrhagic shock
- dengue shock syndrom e
what is the first human disease found to be caused by a virus
yellow fever
what causes yellow fever
- a flavivirus
- a mosquito
- human to human
- monkey to human
what does yellow fever cause in severe cases
- jaundice
- lesions and hemorrhaging of infected organs
what is the treatment for yellow fever
attenuated live vaccine and insect control measures
