9.19 Acute RNA Viruses – Flashcards
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| What enzyme must a negative RNA virus have? |
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| virion transcriptase |
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| Name the naked RNA viruses. |
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| picornaviridae, caliciviridae, astroviridae, reoviridae |
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| T/F Astrovirus contains ds RNA. |
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| false, ss rna |
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| What are the only two examples of diseases in humans caused by reoviruses? |
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| colorado tick fever and rotavirus |
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| Enteroviruses, hepatoviruses, and rhinoviruses are all types of ____ viruses. |
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| picornaviruses |
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| Name the different types of enteroviruses. |
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| poliovirus (3), coxsackie A (1-22 & 24), coxsackie B (1-6), echovirus (1-9, 11-27, 29-34), parechovirus (1-4), kobuvirus (aichi prototype), enterovirus (68-71) |
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| Name the picornovirus that is also a hepatovirus. |
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| hepatitis a |
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| How many different types of rhinoviruses are there? |
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| 1-100+ |
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| Describe picornavirus virions. |
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| small icosahedral, naked virions with + ss RNA. Capsid formed from 60 copies of nonglycosylated proteins |
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| How long does it take for one cycle of replication of a picornavirus? |
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| 6-7 hours |
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| How do picornaviruses leave the host cell? |
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| cell lysis |
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| How do picornaviruses enter the host cell? |
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| attachment then entry via receptor-mediated endocytosis. Receptors are members of the immunoglobulin superfamily |
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| What receptor does polio use? |
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| PVR/CD155 |
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| Of the picornaviruses, most rhinoviruses and several coxsackie viruses use which receptor? |
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| ICAM-1 |
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| Describe the translation of picornoviruses. |
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| proteins translated at one polyprotein and initated at internal ribosome entry site. Polyprotein cleaved by a viral protease. Viral RNA synthesis through "-" strand intermediate with VPg at 5' end. Terminal cleavage of VPO into VP2 and 4 matures particle |
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| Describe the poliovirus polyprotein. |
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| first capsid (P1) then noncapsid genes (p2 and 3) |
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| Describe the characteristics of enteroviruses and Hep A relevant to transmission. |
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| resistant to pH between 3-9, detergents, heat, mild sewage tx |
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| Describe the characteristics of a rhinovirus (picornovirus) relevant to transmission. |
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| labile at acidic pH; optimum gorwth at 33 degrees C |
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| About how many symptomatic infections do enteroviruses cause each year? |
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| 10-15 million |
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| How do enteroviruses get from where they entered the body to where they cause the disease? |
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| intestines-> lymhphoid -> target tissue |
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| There have been no cases of wild poliovirus in the US since ___. |
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| 1979 |
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| IPV (instead of OPV) has been used in the US since ____. |
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| 1999 |
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| What is bulbar paralysis caused by paralytic polio? |
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| when CNs and respiratory center in teh medulla are affected leading to paralysis of neck and respiratory muscles |
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| What are the symptoms of a mild case of polio? |
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| mild fever with diarrhea |
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| T/F Most polio infections are asymptomatic. |
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| true |
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| In what percent of patients is poliovirus replication limited to the GI tract? |
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| 90% |
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| T/F Polio can cause an aseptic meningitis. |
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| true, occurs in about 2% of patients |
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| What parts of the CNS are infected by polio? |
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| anterior horn cells of the spinal cord and motor cortex of the brain |
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| Nuerons can continue to recover from polio infections for how long? |
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| up to 6 months |
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| What are the target tissues of coxsackie A? |
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| herpangina and hand, foot and mouth disease, aseptic meningitis |
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| What are the target tissues of coxsackie B? |
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| myocardial and pericardial infections, pleurodynia, and aseptic meningitis |
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| What are the target tissues of parechovirus? |
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| respiratory and GI, rare encephalitis and myocarditis |
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| What is the target tissue of kobuvirus? |
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| gastrointestinal |
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| What is the target tissue of echovirus? |
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| aseptic meningitis, usually during the summer |
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| Which enterovirus infect the meninges? |
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| echo, polio and cox |
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| Which enteroviruses infect muscle? |
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| echo and cox a and b |
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| Which enteroviruses go on to infect the skin and cause hand, foot, and mouth disease as well as rash herpangina? |
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| echo and cox a |
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| How do you diagnose and treat enteroviruses? |
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| RT-PCR or viral isolation and culture. However, viremia may be undetectable at time of symptoms. CSF specimens during acute phase are positive in 10-85% of samples treatment is supportive care |
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| What is the principle agent of the common cold? |
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| rhinovirus (restricted to upper respiratory tract, causes mild URI in all age groups) |
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| What is the time course of rhinoviruses? |
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| 1-2 day incubation period; acute symptoms last 3-7 days |
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| How do you treat rhinovirus infection? |
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| no specific tx or vaccine (possible block of receptor attachment) |
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| What type of virus is a norovirus? |
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| calcivirus |
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| What are the characteristics of gastroenteritis caused by calciviruses? |
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| family/community-wide |
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| WHat are the characteristics of gastroenteritis caused by astrovirus? |
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| mild, self-limiting, in children |
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| What two factors contribute to a high transmission risk in viruses that cause gastroenteritis? |
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| large quantities of virus in the stool and the virus is resistant to the environment |
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| Describe the calcivirus virion. |
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| naked, icosahedral, positive ssRNA. Contain a single large capsid protein. Viral surface has 32 cup-shaped depressions (calici) |
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| What are the caliciviruses are medical importance? |
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| norwalk and "norwalk like" viruses (NLV) "sapporo-like" viruses (SLV) |
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| What is the primary agent responsible for most acute diarrheal diseasein adults and children? |
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| norovirus (90% of all viral diarrheal disease) |
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| T/F Norovirus is considered ubiquitous. |
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| true, 70% of people have had it by age 7 |
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| What are the different genogroups of norovirus? |
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| GI-V, which are each divided into at least 31 genetic clusters |
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| Which is the most dominant type of norovirus over the last several years? |
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| GII.4 |
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| How many particles of norovirus are needed to cause infection? |
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| 10 |
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| Name the norwalk and norwalk like viruses. |
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| norwalk, hawaii, snow mountain, montgomery county, taunton (england) |
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| What is the time frame of norovirus? |
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| incubation period of 24-48 hours. abrupt onset with watery diarrhea, N/V, lasting 24-60 hours |
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| T/F Most norovirus infections are asymptomatic. |
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| false, around 30% of norovirus infections are asymptomatic |
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| What percent of diarrheal cases in infants does astrovirus account for? |
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| 2-8% |
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| T/F Astrovirus cannot be grown in cell culture. |
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| true |
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| Astrovirus particles are resistant to... |
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| acid stable and heat resistant |
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| Describe Reovirus genome and virion. |
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| ds RNA, segmented genome, icosahedral capsid, naked |
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| What is the leading cause of severe acute gastroenteritis among children worldwide? |
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| rotavirus |
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| Describe the viral nucleocapsid of rotavirus? |
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| composed of three concentric shells that enclose 11 segments of ds RNA |
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| How many serotypes are there of rotavirus? |
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| 5. the outermost layer contains two structural proteins: VP4 (protease cleaved protein, P protein) and glycloprotein (G protein) which dfined the serotype of the virus. Also targets for neutralizing antibodies |
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| T/F Rotavirus is highly contagious. |
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| true |
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| When does rotavirus infection usually occur? |
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| late fall, winter and early spring |
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| What is the disease course of rotavirus? |
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| 1-3 day incubation, followed by abrupt onset of vomiting, abdominal cramps, low-grade fever with frequent copious watery stools |
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| T/F Most children are seropositive for rotavirus by age 3 |
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| true |
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| How do you diagnose rotavirus? |
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| detection of virus particles or viral antigens in the stool |
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| T/F Both rotavirus vaccines are orally administered, non-living virus vaccines. |
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| false they are live virus vaccines |
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| How was Rotateq developed? |
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| contains 5 reassortant rotaviruses developed from human and bovine parent rotavirus strains |
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| RotaTeq contians which antigen? |
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| RV5 pentavalent human-bovine reassortant rotavirus vaccine |
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| What are the doses of rotarix? |
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| 2 doses at 2,4 months of age |
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| What is the antigen used in rotarix? |
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| RV1 (monovalent human rotavirus vaccine) |
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| When were the two rotavirus vaccines liscensed? |
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| rotateq in 2006, rotarix in 2008 |
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| How was rotarix vaccine created? |
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| contains a human rotavirus strain isolated from a child; was first attenuated by passaging 33 times in African green monkey kidney cells, then cloned and further passaged in vero cells |
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| T/F The second infection with rotavirus tends to be less severe than the first infection. |
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| true however niether vaccine nor natural infection will provide full immunity from future infections |
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| What is a possible complication of RotaShield? |
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| intussusception, taken off the market in 1999 |
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| What are the symptoms of colorodo tick fever? |
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| acute disease with fever headache and severe myalgia |
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| Characterize the genome of the virus that causes colorado tick fever. |
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| 12 double stranded RNA genomic segments |
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| Where is reovirus that causes colorado;tick fever;found? |
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| western and northwestern US, western canada; host is the dermacentor andersoni wood tick; natural host are mammals (squirrel, rabbits and deer) |
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| What are the most prevalent and/or significant enveloped RNA viruses? |
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| influenza, paramyxo, and retroviruses |
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| Name the enveloped RNA viruses that cause CNS disease and hemorrhagic fevers? |
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| togaviruses (alpha viruses), flavivirus, and bunyaviruses |
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| Name the togaviruses. |
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| equine encephalitis viruses (EEE, VEE, WEE) chickungunya fever (asia) and rubella (rubi viruses) |
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| Name the flaviviruses. |
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| yellow fever, dengue, st louis encephalitis, west nile, and hep C |
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| Name the bunya viruses. |
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| california encephalitis, LaCrosse encephalitis, Rift valley fever, hantavirus |
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| Where are california and laCrosse encephalitis found and what are they transmitted by? |
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| found in US, transmitted by mosquitoes and chipmunk is a reservoir host |
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| Where is rift valley fever found and what transmits it? |
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| sandflies in Africa |
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| What are the symptoms of hantavirus infection. |
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| hemorrhagic fever and pulmonary syndrome |
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| What population does california encephalitis affect most? |
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| highest rates of disease in children |
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| What time of year is california encephalitis at its peak? |
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| summer |
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| Does california encephalitis predominantly affect suburban or rural environments? |
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| vector is found in both places (aedes triseriatus) |
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| Describe the virion of a togavirus. |
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| SS RNA + enveloped with icosahedral symmetry |
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| How does a togavirus enter a cell? |
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| via receptor-mediated endocytosis |
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| What is alphavirus? |
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| insect borne encephalitis |
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| What causes rubella? |
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| rubivirus |
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| T/F Rubella is insect borne. |
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| FALSE! |
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| What is the natural host of an alphavirus and how is it transmitted? |
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| mammal or bird with no apparent disease; transmitted by mosquitoes |
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| Why is is alphavirus only trandmitted by mosquitoes? |
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| viral replication in gut of vector is essential |
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| Describe the pathogenesis of alpha virus. |
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| infected arthropod bites and injects virus from salivary glands to capillary bed. Then the virus replicates in the reticuloendothelial system. The systemic phase with symptoms of viremia and fever. Then there is active infection of target tissue (CNS or skin and blood vessels, or viscera and muscle) |
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| What organisms are infected by alphaviral encephalitides? |
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| found principally in horses (and humans) as accidental dead-end hosts from enzootic transmission from birds or rodents |
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| What are the different types of alphaviral encephalitides? |
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| EEE (eastern equine encephalitis), WEE (western), VEE (Venezuelan) |
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| Which is the most severe of the alphaviral encephalitides? What's the mortality? |
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| EEE, 33% mortality with severe neurological sequelae |
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| Where is EEE found? |
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| EE is very rare but it is found in atlantic and southern coastal states |
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| Where does EEE come from? |
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| reservoir in birds, possibly pheasants, bird-bird transmission |
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| T/F Most people recover completely from WEE. |
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| true, there is a 2-3% mortality |
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| What are the symptoms of WEE? |
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| more frequently symptomatic in children and range from mild flu-like to encephalitis |
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| How is WEE transmitted? |
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| bird-mosquito-bird |
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| Where is WEE found? |
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| mostly in western and mid-western states but range of bird and vector rules, so not restricted there |
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| What is the mortality rate of VEE? |
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| very low (0.5%) in humans but devastating for horses |
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| How is VEE transmitted? |
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| reservoirs in rodents rather than birds |
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| Where is VEE found? |
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| chiefly south america and southern US |
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| Where is chickungunya fever found? |
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| asia, thailand, maylasia, india |
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| What are the symptoms of chickungunya fever? |
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| debilitating illness with fever, h/a, fatigue, N/V, muscle pain and joint pain |
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| What is the treatment for Chickungunya fever? |
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| there is no tx or vaccine |
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| What is the viral vector of chickungunya fever virus? |
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| aedes albopictus |
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| What are the flaviviruses? |
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| yellow fever, denque, st. louis encephalitis, west nile and hepatitis C |
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| Describe the virion of flaviviruses. |
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| SSRNA +, enveloped, and icosahedral |
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| What type of virus is yellow fever? |
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| flavivirus |
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| Which virus type cause encephalitis and hemorrhagic fever? |
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| encephalitis hemorrhagic fevers |
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| What are the encephalitides of the flavivirus? |
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| st. louis encephalitis (US-Canada), Japanese B encephalitis (Asia, pigs, and birds) murray valley fever (australia), west nile fever (widespread), powassan virus (North America-tickborne) |
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| Which flaviviruses cause hemorrhagic fevers? |
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| yellow fever and dengue |
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| What are the symptoms of flaviviral encephalitis? |
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| fever, h/a, chills, vomiting; drowsiness and nuchal rigidity 1-2 days later. May progress to confusion, convulsion, coma and death |
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| What are the symptoms of yellow fever? |
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| chills and fever followed by visceral infection of liver and/or kidneys. GI hemorrhage and characteristic black vomit |
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| What is the mortality of yellow fever? |
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| 10% |
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| How can you prevent yellow fever? |
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| live, attenuated 17D vaccine |
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| What are the natural host of yellow fever? |
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| monkeys and man |
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| How is yellow fever transmitted? |
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| sylvatic cycle and urban cycle (human-mosquito-human) cycle; man not necessarily dead-end |
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| Where is Yellow Fever found? |
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| sporadically in the forested areas of south america and in afra during the rainy season |
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| What is the most widespread arbovirus in the world? |
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| dengue fever |
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| How many cases of dengue fever are there per year? |
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| 100 million cases/year |
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| Where in the US is Dengue fever found? |
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| texas and florida keys |
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| Can you be infected with Dengue fever multiple times? |
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| yes, there are 4 serotypes |
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| How is Dengue fever transmitted? |
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| between mosquitoes and humans (aedes aegypti). Transmission occurs when mosquito feeds on a person during a 5 day period when large amounts of virus are in the blood |
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| What has caused Dengue to disseminate around the world? |
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| transport of aedes mosquitoes around the world (WWII) |
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| Where is denque fever found? |
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| endemic in asia, the pacific, the americas, africa, and the caribbean |
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| What is the time course of the symptoms of Dengue fever? |
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| begin 4-7 days after the mosquito bite and typically last 3-10 days. Causes severe headache and severe pains in muscle and joints ("breakbone fever") rapidly fading maculopapular rash; hematuria, leukopenia, thrombocytopenia. Convalescence slow but certain |
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| What is Dengue hemorrhagic fever? |
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| aka dengue shock syndrome. Occurs upon re-infection with another serotype, immune complex type of disease, circulatory shock and hemorrhage, high mortality, esp in children |
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| What is the time course/symptoms of dengue hemorrhagic fever/dengue shock syndrome? |
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| fever lasts from 2 to 7 days. As fever declines symptoms including persistent vomiting, severe abdominal pain, and difficulty breathing may develop. Capillaries become permeable causing ascites and pleural effusions, leading to shock and death |
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| Dengue epidemics require.. |
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| large number of vector, large numbers of people with no immunity to dengue, the opportunity for contact between the two |
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| How do you tx dengue HF? |
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| treat symptoms 1) blood/platelet transfusion 2) IV fluids/electrolytes 3) oxygen therapy |
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| What is the prognosis for dengue HF? |
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| most pts recover with early and aggressive care. Half of untreated pts who go into shock don't survive |
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| Where/when was west nile fever virus found in the US? |
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| 1999, NY metro area |
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| T/F Most humans develop no clinical signs of disease when infected with west nile. |
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| true (only 20% develop disease of west nile fever) |
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| Which populations have the most severe cases of west nile? |
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| the elderly |
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| How do you prevent west nile fever? |
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| aggressive mosquito control (birds are now uniformly infected) |
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| What test is used by blood banks to determine that donated blood does not contain west nile virus? |
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| nucleic acid amplification test (NAAT) |
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| When are levels of WN virus highest? when are IG levels highest? |
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| about 3 days before symptom onset 2-3 days post onset |
