Term
| what are the nationally reportable viral causes of encephalitis/meningitis? |
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Definition
| poliovirus and arbovirus (st. louis, west nile, powhassan, eastern/western equine, california serogroup - la crosse) |
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Term
| what family does the poliovirus belong to? what characterizes this family? |
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Definition
| poliovirus (human enterovirus A) is a part of the enterovirus family (coxsackie virus [human enterovirus B and C], echovirus [human enterovirus D], enterovirus), a group of viruses which are spread fecal-oral through the GI tract (and sometimes respiratory) and many cause meningitis. most are prevalent in the summer/fall and many infections are asymptomatic. usual symptoms: cold/flu-like illness, rash, and aseptic meningitis - type of illness is determined by serotype of virus/age/immune status of pt (most common cause of viral meningitis in younger children - less Ab). |
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Term
| what is the most common cause of aseptic meningitis especially in children? |
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Definition
| enteroviruses. common symptoms: fever, severe h/a, stiff neck, photophobia, drowsiness, confusion, and n/v. duration is 7-10 days and rarely fatal (no antivirals). |
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Term
| what was the most common serotype of enterovirus responsible for myocarditis, aspeptic memningitis, and neonatal systemic illness in 2007? |
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Definition
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Term
| what is the epidemiology of poliovirus? |
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Definition
| crowding, poor hygiene, poor sanitation = infection in young children/adults. if this is improved, most infections are then seen affecting older age groups. polio-endemic countries: nigeria, afghanistan, india, and pakistan. |
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Term
| what is the course of polio infection? |
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Definition
| replication at the site of entry (oropharynx, GI tract) and dissemination (virus crosses BBB and infects axons of peripheral nerves: motor neurons, anterior horn of spinal, cord, medulla, cerebellum, cortex) |
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Term
| what is the clinical disease due to polio infection? |
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Definition
| 1) abortive poliomyelitis (no CNS dissemination = initial replication only, 7-14 day incubation, flu-like symptoms). 2) nonparalytic/aseptic meningitis (previous s/s + stiffness, pain in back of neck = usually complete recovery after 2-10 days). 3) paralytic poliomyelitis (most severe form = above symptoms + flaccid paralysis, spinal poliomyelitis is temporary up to 6 mos and permanent thereafter - ~1% of cases). |
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Term
| what is post-polio syndrome? |
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Definition
| new & progressive muscle weakness, fatigue, pain, trouble breathing, swallowing which occurs at least 15 yrs after acute paralytic poliomyelitis in former polio survivors from the pre-vaccine era. hard to dx, though to be related to persistent virus or overworked nerves (surviving neurons compensate w/higher axon production). this cannot be reversed, but can be stabilized. |
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Term
| what vaccines are available for polio? |
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Definition
| 1) salk vaccine: fomalin *inactivated polio vaccine (IPV), contains all 3 serotypes. 2) sabin vaccine: oral polio vaccine (OPV), protects against all 3 serotypes, *live attenuated which replicates in the gut and is shed in the stool - but 1 in 2 million will get vaccine-associated disease (VDPV). |
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Term
| how do the IPV and OPV compare? |
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Definition
| IPV/salk is safe for immunodeficient pts (no risk of polio) and can be combined w/other vaccinations. OPV/sabin will get IgA response in the GI = herd immunity (fecal oral transmission of vaccine), easily administered and higher level of seroconversion after a single dose - but risk of vaccine derived polio virus (VDPV). |
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Term
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Definition
| the OPV vaccine can lose its attenuated mutations and become more like the wild type either due to continuous replication in an immunodeficient individual (iVDPV), as circulation in a population w/low vaccine coverage (cVDPV), where it may recombine w/other enteroviruses or as a clinical isolate from pts w/no known immunodeficiency/sewage isolate from an unknown source = ambiguous VDPV (aVDPV). VDPV outbreaks occur in regions of low vaccine coverage. |
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Term
| what are common case examples of iVDPV? |
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Definition
| immunocompromised pt is exposed to OPV by household member which replicated and mutated for years, eventually resulting in acute flaccid paralysis. poliovirus type 1 has been IDed in immunocompromised (SCID) infants - **more common in B-cell deficient pt rather than T-cell deficient ones** in amish communities. and even non-immunocompromised non-vaccinated pts may contract polio from exposure to OPV-vaccinated pts. |
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Term
| what is the polio vaccination policy in the US? |
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Definition
| 1997 - 2 doses of IPV, 2 doses of OPV (start developing an immune response with IPV and then have no chance of developing VDPV with the OPV). 1999 - all 4 IPV b/c parents have been rejecting the last 2 OPV doses. OPV is still recommended for mass vaccination campaigns (easier to use/administer) and for people about to travel to endemic areas (faster immune response). |
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Term
| what is the most common sporadic cause of viral encephalitis? |
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Definition
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Term
| what is the most common cause of viral meningitis/encephalitis outbreak? |
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Definition
| arboviruses (and enteroviruses). arboviruses are arthropod-borne (not a family itself) and are composed of the 3 families: togaviruses, flaviviruses, and bunyaviruses. |
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Term
| what arboviruses are seen in the US? |
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Definition
| st. louis, west nile, powhassan (tick-borne), eastern/western equine, and california (la crosse) |
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Term
| what characterizes the togaviridae? |
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Definition
| +s RNA, icosahedral, enveloped. important viruses: EEE, VEE, WEE |
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Term
| what characterizes the flaviviridae? |
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Definition
| +s RNA, enveloped. important viruses: dengue, japanese, russian spring-summer, st. louis, west nile, powhassan, yellow fever encephalitis. |
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Term
| what characterizes the bunyaviridae? |
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Definition
| -s RNA, 3 segments: helical/enveloped. important viruses: rift valley fever, california, la crosse encephalitis. |
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Term
| what is the course of arbovirus infection? |
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Definition
| virus enters via mosquito, replication in vascular endothelial & lymphatic cells (may be asymptomatic) may be cleared at this point, or viremia/dissemination to CNS/other organs = flu-like illness and potentially severe systemic disease. |
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Term
| what characterizes clinical disease due to arboviruses? |
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Definition
| many infections are asymptomatic. generally less severe than bacterial meningitis - but may involve coma, seizures, paralysis, and brain damage |
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Term
| what is the most severe arbovirus infection? |
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Definition
| equine encephalitis (~1/3 fatality rate) |
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Term
| what is the transmission cycle for arboviruses? |
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Definition
| small animals are the reservoir, which mosquitoes transfer from to larger hosts horses/humans = dead end host/incidental infection (not enough in blood for mosquito to pick up again from). |
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Term
| what characterizes epidemiology of arbovirus break-outs? |
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Definition
| equine encephalitis may forewarn of human epidemic. birds are monitored for west nile (most important in US). japanese encephalitis is the most important worldwide. |
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Term
| what characterizes japanese encephalitis virus (JEV)? |
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Definition
| JEV is the most common vaccine-preventable cause of encephalitis in asia. hosts are primarily *pigs and wading birgs -> mosquito -> human. |
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Term
| where are the arboviruses seen geographically in the US? |
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Definition
| western/eastern equine viruses: obvious. california serogroup virus (la crosse): eastern US, texas, montana, and california. st. louis encephalitis: everywhere more or less. west nile: mostly midwest. powhassan: NY state. |
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Term
| what characterizes the west nile virus (WNV)? |
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Definition
| flavivirus, related to st. louis/japanese (Abs can cross-react), but causes a milder disease (usually not virulent for birds). initial outbreak in NYC 1999 = 54 cases/6 deaths, response = pesticide+prevention. |
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Term
| what characterizes arbovirus transmission? |
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Definition
| through mosquito, blood transfusion (donor may be Ab negative but Ag positive), organ transplant, and breast feeding |
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Term
| what characterizes prevention for arboviruses? |
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Definition
| surveillance (animal hosts), reduce mosquito population, reduce mosquito exposure, and vaccines (available for EEE, WEE, VEE, JE) |
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Term
| what characterizes the virus responsible for rabies? |
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Definition
| bullet shaped helical RNA enveloped virus (rhabdovirus), highest fatality rate - essentially fatal w/symptomatic illness (has already reached CNS) |
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Term
| who are hosts for rabies? |
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Definition
| all mammals, in US = bats are most common (pt may be unaware), globally = dogs/cats/cows. skunks/raccoons/foxes/coyotes also common in US. |
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Term
| what is the epidemiology of rabies? |
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Definition
| incidence in US has decreased since vaccination of pets, more common in india. |
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Term
| what characterizes the infectivity of rabies? |
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Definition
| animal bite to face: 60% chance of infection, hands/arms: 15-40%, leg: 3-10% chance. transmission is less possible through scratches and even less possible through aerosol (spelunking). once virus dries out, it loses its infectivity. |
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Term
| what is the course of rabies infection? |
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Definition
| replicates initially in muscle/connective tissue: 3-8 wk incubation (shorter w/head bite, larger inoculums), enters peripheral nerves at neuromuscular junctions. need to prevent CNS dissemination to prevent fatality (90%+ fatality rate, severe encephalitis). once in CNS, rabies disseminates back to salivary glands, other tissues - transmission via saliva (not viremia). |
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Term
| what is the clinical disease due to rabies? |
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Definition
| initially: abnormal sensations near wound, malaise, h/a, n/v, sore throat, and fever. hydrophobia due to painful spasmodic contractions of muscles involved in swallowing - drool to avoid swallowing. CNS symptoms: dilated pupils, hallucinations, muscle spasms, anxiety, convulsions/seizure/coma, death in 3-5 days (usually due to respiratory paralysis). extensive CNS damage: demyelination of cerebral cortex, cerebellum, hippocampus, and DRG. |
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Term
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Definition
| usually associated w/a hx of exposure. *negri bodies (cytoplasmic inclusion bodies) which are aggregates of viral nucleocapsids may/may not be seen. IF staining for viral antigens (brain tissue, corneal epithelial cells, skin bx from nape of neck). isolation of virus (brain or saliva or cell cx from inoculate infant mouse). serology (can be initially negative). RT-PCR+sequencing (sensitive). |
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Term
| what characterizes the vaccines available for rabies? how should a pt potentially exposed to the virus be treated? |
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Definition
| live, attenuated vaccines have been used for dogs, cats, cattle. the 2 vax available for humans in the US are inactivated and considered equally safe/efficacious. rabies Ig (RIG) products are also available (prepared from hyperimmunized human donors). *both the vax and RIG should be given to a pt potentially exposed to the virus. |
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Term
| who is pre-exposure tx (inactivated vaccine) recommended for? |
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Definition
| pts at risk for rabies exposure: vets, pts in contact w/wildlife, spelunkers, and those traveling to endemic areas |
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Term
| what characterizes post exposure rabies prophylaxis? |
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Definition
| wound tx for humans: cleaning and local administration of RIG/vax if pt was not previously given RIG, only vax if pt was previously given RIG. overall goal is confine the virus to site of entry. observe domestic animals for 10 days (if no s/s, then give vax), kill+examine wild animals immediately. |
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Term
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Definition
| a naked icosahedral ds DNA polyomavirus which produces *T antigens which bind and inactivate p53/Rb - sending cells through the cell cycle, facilitating productive viral replication in permissive cells and may result in transformation in nonpermissive cells. |
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Term
| what is the course of JC virus infection? |
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Definition
| thought to enter via respiratory tract, disseminates to the kidney via viremia, latently infects the kidney/B cells/monocyte-lineage cells. latent infection unless immunocompromised = 2ndary viremia/dissemination to the CNS = productive lytic infection in oligodendrocytes, leading to demyelination and possible transformation in glial cells. |
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Term
| what is progressive multifocal leukoencephalopathy (PML) as caused by JC virus? |
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Definition
| a demyelinating disease occurring in immunocompromised pts, affecting speech/vision/coordination/mental ability, paralysis of arms/legs, progressing to death. this occurs in 10% of AIDS pts. fatal in 90% of cases after 1-4 mos. dx: PCR detection of viral DNA in CSF *and MRI/CT evidence of lesions in white matter. |
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Term
| what tumors can be caused by JC virus? |
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Definition
| medulloblastoma, oligodendroglioma, astrocytoma, glioblastoma, ependymoma |
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Term
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Definition
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Definition
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