Virology Flashcards
1
Q
Rabies Virus
A
- Family: Rhabdoviridae “bullet” shape enveloped, negative-sense, single-stranded RNA virus
- Genus: Lyssavirus
- Reservoir: Bats and Skunks
- Spillover into accidental hosts such as man, fox, domesticated animals…
- Rabies is a severe acute progressive encephalitis
- Neurotropic virus: replicates in nerves and brain
- No viremia (not detected in blood/serum)
- Almost invariably fatal (Respiratory arrest)
- Variable incubation period (2 weeks -years)
- All mammals are susceptible
- Typically transmitted via saliva following a bite
- Travels to central nervous system (CNS) via retrograde axonal transport
- Following replication in CNS, virus travels through axons to salivary glands where it is excreted in the saliva
- Rabies Neutralizing Titer
- RFFIT
- Rapid Fluorescent Foci Inhibition Test (neutralization test)
- PRIMARY RABIES ASSAY: Direct Fluorescent Antibody Test
- Rabies DFA
- Direct Detection
- DFA (Primary)
- RT-PCR
- Direct rapid immunohistochemicaltest (DRIT)
- Virus isolation
- Mouse neuroblastomacell culture
- Mouse inoculation
- Sellers stain for Negribodies (no longer in use)
- Real-time RT-PCR (in progress…)
- Serologic Diagnosis
- IFA
- RFFIT
- Negri bodies
- Historically important, discovered by Negri in 1903.
- Sellers stain may reveal oval inclusions in the cytoplasm of nerve cells of animals with rabies (called Negri bodies)
- Not sensitive or specific enough for diagnostic testing
- NOT pathognomonic for rabies!!
- Still used in areas with no access to other methods of testing
2
Q
Rabies Law
A
California Health and Safety Code
- Laws on quarantine
- Laws on dog vaccination
- Laws on laboratory testing: “If any rabid animal, clinically suspected rabid animal or biting animal dies or has been killed, adequate specimens must be obtained and examined in a public health laboratory approved by the department
- Mandatory reporting of rabid animals to local health department immediately
- Must also report rabid livestock to CDFA
- Local animal control jurisdictions must provide annual summary of rabies activities to State Veterinary Public Health Section
3
Q
Laboratory Diagnosis In Humans Ante-mortem
A
- 1) Serum
- –IFA, starting dilution is 1:4
- –RFFIT
- 2) CSF
- –IFA, starting dilution is 1:2
- –RT-PCR
- 3) Saliva
- –RT-PCR
- –Culture in NB2A cells
- 4) Nuchal Biopsy (hair follicle from nape of neck)
- look for rabies antigen in cutaneous nerves surrounding hair follicles
- –DFA
- –RT-PCR
- 5) Corneal Impressions no longer recommended
- –DFA
4
Q
Rabies Anatomy
A
- Brain stem (BS) and Cerebellum (CB)
- Animal Brain Tissue
- Necropsy must be performed to remove the brain
- Complete cross section of brain stem is crucial for testing!!!!!
- Complete cross section of the Cerebellum (left and right lobes, and vermis)
- Optional: complete cross section Hippocampus (cerebellum is preferred)
- For bats, the whole brain is used to make slides
- Appropriate number of slides must be made from specific areas of the brain
- For larger animals (cow, horse) make slides from cerebral cortex too!
- Make tissue impression slides
5
Q
Rabies DFA
A
- Human Exposure to High Risk Animal
- Make a minimum of 4 slidesfrom cross-sections of:
- Brain Stem (BS) –ENTIRE cross-section
- Cerebellum(CB) including left and right lobes, and vermis
- AND/OR (if no cerebellum)
- Hippocampus(HP): left and right
- Make minimum of 10 slides from large animals
- Make 2 slides from bats
- Positive and Negative Control Slides
- Positive brain material
- Animals naturally infected with the most common rabies variant from the submitting area for the laboratory should be used as positive control
- State rabies lab previously tested positive animal with CA skunk rabies variant as positive control(staining 4+/4+)
- Negative brain material
- Previously tested animal brain known to be negative
- Storage of Control Slides
- Slides are prepared in advance and stored at -70°C. Slides are thawed then fixed on same day as specimen is tested
6
Q
Parvoviridae
A
ss(- or +) Linear DNA with no Envelope
Slapped Cheek
7
Q
Hepadnaviridae
A
DS DNA, Linear with envelope
8
Q
Herpesviridae
A
DS DNA LINEAR with envelope
9
Q
Poxviridae
A
DS DNA linear with double envelope
Pox carriesa DNAdDNApol!
10
Q
Papillomaviridae
A
DS DNA circular no envelope
11
Q
Adenoviridae
A
DS DNA Linear with no envelope
12
Q
TORCH
A
- Pneumonic for pathogens that cross the placenta and may affect the developing fetus
- Toxoplasma gondii
- Other –Syphilis, Listeria, Brucella, Zika, ParvoB19
- Rubella
- CMV
- HSV
13
Q
RNA Viruses–Key Concepts
A
- RNA genomes may be single- or double-stranded (ss or ds);
- haploid (1), diploid (2); linear, circular, segmented
- ss (+)sense RNA genomes are translation-competent upon release, i.e., essentially they are like mRNA
- ss (–)RNA is “anti-sense”, meaning it needs to be transcribed by a viral polymerase to mRNA before viral proteins can be made
- All RNA viruses encode a viral polymerase
- In (-)sense RNA viruses, this polymerase is carried in the virus, ready to be used when the virus infects a cell (“Virion-associated”)
- Diploid ss (+)sense RNA viruses (Retroviruses) are special.
- They are the only RNA viruses known to go through a DNA phase in their replication cycle
14
Q
Picornaviridae
A
- sense ssRNA
- Enterovirus (15)
- Hepatovirus(9)
- Polio, enteros,rhinos HepatovirusA (HAV)
- No envelope
- Rash, encephalitis, Hepatitis
- Fecal-oral(polio, HAV), fomites, and/or respiratory (enteros, rhinos)
- Hepatovirus: Hepatitis A virus
- Cardiovirus: Encephalo-myocarditis virus
- Kobuvirus
- Cosavirus
- Apthovirus: Foot-and-mouth disease virus
- Teschovirus
15
Q
Togaviridae
A
- Toga, meaning thick envelope
- (+) ssRNA, 50-60nm enveloped icosahedrons, 2 glycoproteins
- Genus Alphavirus:
- A large genus of mosquito-borne viruses
- 32 species, transmitted by mosquitoes
- E.g., Chikungunya, WEE, EEE, VEE*
- All medically important alphaviruses are arthropod-borne (e.g. mosquito vectors) and have non-human hosts
- Humans tend to be “dead-end” hosts (don’t transmit to others): Except CHIK
16
Q
Retroviridae
A
- diploid (+) ssRNA(2 copies)
- HTLV and HIV
- “Reverse Transcriptase”:
- ssRNA dsDNA via virus-encoded RNA-dependent DNA polymerase (RdDp)
- Enveloped, SS, diploid, + sense, RNA
- Integration of Viral Genome into Host DNA
as a Provirus - Latency
- Oncogenic and Cytopathic varieties
17
Q
(-) ssRNAViruses
A
- All are enveloped viruses
- These viruses also must carry an RNA-dependent RNA polymerase (RdRp) in order to make positive sense of mRNA
- Paramyxo
- Measles, Mumps
- Syncytia, also known as multinucleated giant cells, visible by staining
- Orthomyxo- InfluenzaA (H1N1)
- Influenza B
- Bourbon
- Filo-Zaire Ebolavirus
- Marburg
- Rhabdo-Rabies
- Hanta-SinNombre
18
Q
Reoviridae
A
- dsRNA Respiratory Enteric Orphan viruses
- No envelopes
- Triple layered: outer & intermediate layers and an inner core
- 11 segments dsRNA
- Carries RNAdepRNApol
19
Q
Order Rickettsiales
A
- Small obligate intracellular bacteria
- 0.3 to 0.5 um by 1 to 2 um
- Gram-negative cell wall structure
- Poorly staining
- Rickettsiagroup specific LPS; Orientialacks LPS
- A+T-rich genome
- Lack genes for sugar metabolism, lipid biosynthesis, nucleotide synthesis, and amino acid synthesis
20
Q
Rickettsiales: Common Features
A
- Arthropod Vectors: ticks, fleas, mites, or lice
- Geographic distribution is determined by vector
- Most are Zoonoses
- Don’t survive outside living host for long (R. prowazekii exception)
- Similar disease syndrome that may differ in severity
- Fever, Headache, Eschar (dark, scabbed plaque overlying a shallow ulcer), Rash(vasculitis)
- “Undifferentiated febrile illness”
- Lab Values: Thrombocytopenia, Elevated Hepatic Transaminases, Hyponatremia
- Susceptible to tetracycline/doxycycline
- Prevention through vector control and sanitation measures
21
Q
Rickettsia Detection
A
- Microscopy
- Gimenezor Wright-Giemsa stain of blood smears and buffy coat
- Morulae in cytoplasm of Ehrlichia-and Anaplasma-infected leukocytes
- Culture
- Cannot be isolated by standard blood culture
- Grow in cell culture (Vero E6)
- R. rickettsiiis a biosafety level 3 agent(high rate of laboratory-acquired infections)
- Immunohistochemistry
- CDC
- Nucleic Acid Amplification
- Specimen Types
- Whole blood: best for Ehrlichiaand Anaplasma
- Tissue (eschar, skin biopsy, CSF) best for SFG Rickettsia
- Antibiotic treatment decreases PCR sensitivity
- Species-level identification possible
- Specimen Types
- Serologic Detection
- Indirect Immunofluorescence Antibody Assay (IFA)
- Group-level Identification (TG vs. SFG)
- Four-fold rise in titer is diagnostic
- Highly sensitive 2-3 weeks after onset; insensitive during 1stweek (Effective anti rickettsial treatment of RMSF must be initiated within 5 days of onset)
- Weil-Felix Test (historical)
- Agglutination through cross-reaction with P. vulgaris somatic antigens
- Indirect Immunofluorescence Antibody Assay (IFA)
22
Q
Rickettsia by Disease
A
- Typhus Group
- Epidemic Typhus
- Murine Typhus
- Scrub Typhus
- Spotted Fever Group
- RMSF
- MaculatumInfection
- Pacific Coast Tick Fever
- Rickettsialpox
- Anaplasmosis and Ehrlichiosis
23
Q
Epidemic Typhus
A
- Agent: R. prowazekii (pronounced “prowachecki”)
- Select Agent: weaponized and antibiotic resistant strains developed
- Transmission
- Reservoir: Humans; Glaucomysvolans (Southern Flying Squirrel)
- Vector: Pediculus humans corporis (louse) (Infects midgut)
- Epidemiology
- Worldwide: associated with unsanitary, crowded conditions
- 3 million deaths during WWI
- Large outbreaks in refugee camps
- Sylvatic Typhus: Contact with flying squirrel nests (fecal dust inhalation?)
- Distribution: Eastern states
- Worldwide: associated with unsanitary, crowded conditions
- Signs/Symptoms
- IP: 7-14 days
- ILI, N/V, cough, maculopapular rash, confusion
- Brill-Zinsser: subclinical persistence; relapse months to years after first onset
- Case-fatality Rate: 10-30% if untreated
24
Q
Murine Typhus (Endemic)
A
- Agent: R. typhi
- Transmission
- Reservoir: Rats, Cats, Opossum
- Vector: Xenopsyllacheopis(Rat flea), Ctenocephalidesfelis(Cat flea), Leptopsylliasegnis(Mouse flea)
- Epidemiology
- Worldwide: tropical and subtropical climates
- United States: California (Los Angeles, Orange counties), Hawaii, Texas
- Signs/Symptoms
- IP: 7-14 days
- ILI, N/V, cough, maculopapularrash
25
Q
Scrub Typhus
A
- Agent: Orientiatsutsugamushi
- Transmission
- Reservoir: Rodents
- Vector: Infected chiggers (larval thrombiculidmites)
- Epidemiology
- “World’s most important Rickettsialinfection in terms of disease burden” –nearly 1 million cases per year
- Southeast Asia, Indonesia, China, Japan, India, Northern Australia
- Rural areas with mite-harboring vegetation
- Signs/Symptoms
- IP: 7-10 days
- ILI, Eschar, Mental Changes, Enlarged Lymph Nodes, MaculopapularRash (25-50% of cases)
26
Q
Rocky Mountain Spotted Fever (RMSF)
A
- Agent: R. rickettsii
- Infects vascular endothelial cells
- BSL-3 level pathogen
- Transmission:
- Reservoir: Rodents, Dogs,
- Ticks (transovarial)
- Vector:
- Dermacentorvariabilis(American dog tick); eastern US, central US, and pacific coast
- D. andersoni(Rocky Mountain wood tick); western US
- Rhipicephalus sanguineus(brown dog tick); Arizona
- Spent 95% of life hidden in cracks/crevices of human habitations
- Epidemiology
- Incidence: 8.9 cases per million
- Arizona Indian reservations: 1,360 cases per million
- Arkansas, Missouri, North Carolina, Oklahoma, and Tennessee account for 63% of cases
- Baja California: 4,300 cases from 2009-2019
- Hyperendemicity linked to an overabundance of tick-infected, free-ranging dogs
- Signs/Symptoms
- Incubation Period: 3-12 days
- Fever, ILI, spotted or generalized maculopapular rash (palms and soles)2 to 4 days after fever, GI involvement; rare inoculation eschar
- Late stage manifestations: meningoencephalitis, acute renal failure, ARDS, shock
- 5-10% case-fatality rate
- The majority of broad spectrum antibiotics are not effective against Rickettsia, Ehrlichia, or Anaplasma
27
Q
Rickettsialpox
A
- Agent: R. akari
- Infects macrophages
- Transmission
- Reservoir: House mice, wild rodents
- Vector: Mite
- Epidemiology
- Distribution: Former Soviet Union, South Africa, Korea, Turkey, Balkan region, USA (New York –5 cases annually)
- Signs/Symptoms
- IP: 10-14 days
- ILI, eschar, vesicular rash, thrombocytopenia
- Chickenpox differential dx
28
Q
Anaplasmosis (Human Granulocytic Anaplasmosis)
A
- Agent: Anaplasma phagocytophilum
- Infects granulocytes
- Transmission
- Reservoir: Small mammals, rodents, deer, dogs
- Vector: I. scapularis, I. pacificus
- Epidemiology
- Incidence: 6.3 cases per million
- US Distribution: Northeast and upper Midwest
- CA Reportable Condition: 5 cases per year
- Signs/Symptoms
- IP: 5-14 days
- Systemic inflammatory response; Leukopenia
- ILI, rash (rare), severe clinical course possible
- Co-infections with Borrelia, Babesia, Powassanvirus
- Case-fatality rate < 1%
29
Q
Ehrlichiosis (Human MonocyticEhrlichiosis)
A
- Agent: Ehrlichia chaffeensis
- Infects monocytes and tissue macrophages
- Transmission
- Reservoir: Deer, rodents, dogs
- Vector: Amblyommaamericanum(Lone Star Tick)
- Epidemiology
- Incidence: 3.2 cases per million
- US Distribution: Southeast esp. Arkansas, Missouri, Oklahoma, Tennessee, and Virginia
- CA Reportable Condition: 1 case per year
- Signs/Symptoms
- IP: 5-14 days
- Leukopenia
- ILI, GI and Neurologic manifestations, variable pattern Rash (adults = 30%, children = 60%), cough/respiratory symptoms, meningoencephalitis
- Case-fatality rate: 3%
30
Q
Query (Q) Fever
A
- Agent: Coxiella burnetii
- Obligate Intracellular Bacteria
- Anexic(cell-free) culture possible
- Gammaproteobacterium, Legionellales, Coxiellaceae, Coxiella
- Select Agent (BSL3)
- Transmission:
- Reservoir: Domestic Livestock
- Vector: None
- Inhalation of aerosols from urine, feces, amniotic fluid, and placental tissue; unpasteurized dairy products
- Infectious dose: 1 spore
- Epidemiology:
- Occupational disease: Farmers, Vets, Abattoir workers
- Worldwide distribution; Geocentric: California, Texas, Colorado, Illinois
- Seroprevalence= 3.1%
- Netherlands OB: 4,000 cases associated with goat dairy farms
- Pathogenesis:
- Infects alveolar macrophages
- Prevents phagolysosome fusion and activation of apoptosis by high jacking host cell signaling pathways
- Signs/Symptoms:
- IP: 2-3 weeks
- ILI, prolonged high fever (105°F), pneumonia, hepatitis, rare rash
- Chronic Form: relapse months to years after onset; endocarditis
- Laboratory:
- Select Agent!
- Serology (IFA), PCR, IHC, Cell culture
- Acute Infection: antibodies to phase II antigens(avirulent, high passage form) predominate
- Chronic Infection: antibodies to phase I antigens(virulent form) predominate
- Treatment: Doxycycline for 2 weeks (acute) or several months (chronic)
31
Q
Zika Virus
A
- General
- 1st isolated from a sentinel Rhesus macaque –Zika Forest in Uganda in 1947
- Zika virus is a mosquito-borne flavivirus similar to dengue, yellow fever, West Nile, and Japanese encephalitis viruses
- Like dengue and chikungunya, Zika isolated from Aedes mosquitoes
- Zika virus Infections
- Generally, mild febrile rash illness lasting 2-7 days
- 4/5 people infected are asymptomatic
- Symptoms most commonly reported:
- Fever
- Maculopapular skin rash
- Conjunctivitis
- Muscle and joint pain
- Malaise
- Headache
- Rarely severe or fatal illness
- Zika Microcephaly
- Definition: Head circumference at birth >2 standard
deviations below the mean for gestational age and sex - Outcomes:
- Range from normal to severe, including death
- Can include seizures, visual or hearing deficits
- Correlate with severity of microcephaly
- Causes:
- Congenital infection: e.g. syphilis, rubella, toxoplasmosis
- Genetic disorders and inherited mutations
- Other brain injuries: hypoxia, drugs, toxins, FAS
- Epidemiology:
- 2‐12/10,000 live births in US
-
Guillain‐BarréSyndrome (GBS)
- Autoimmune neurologic disease causing weakness and/or paralysis
- Outcomes:
- Respiratory weakness needing ventilatory support in 10‐30%
- Autonomic dysfunction in 70%; can lead to sudden death
32
Q
Zika Virus Detection
A
- Zika viremia is low and of short duration
- Viral loads <3.5 X 103 viral particles/ml compared to ~107–108 for dengue and chikungunya (Lanciotti et al., 2008)
- The virus is often no longer detectable in serum at or shortly after symptom onset
- Most detections of Zika virus by RT-PCR in serum: <3 days of illness onset
- Zika-specific IgM can appear later in course of infection
- Samples collected <7 days after onset can be falsely negative
- Zika virus IgM may persist as long as dengue virus IgM (~12 weeks) –little data
- Flavivirus-specific antibodies (IgM & IgG) cross-react requiring confirmation
- No good tests available to diagnose acute Zika virus disease
- Prolonged ZIKVIgM may make it difficult to determine timing of infection
-
RT-PCR
- Sensitivity:
- Serum = 51%
- Urine = 90.62%
- Specificity of urine or serum PCR = 100%
33
Q
Ebola virus disease (EVD)
A
- Filoviridae
- 8 genera
- Enveloped virus
- 19 kb linear ssRNA
- RNA dependent RNA polymerase
- Marburg (1967) and Ebola (1976)
- Ebola virus Genus
- 6 Species
- Zaire ebolavirus = Ebola virus
- Sudan ebolavirus = Sudan virus
- Bombali ebolavirus
- Bundibugyo ebolavirus
- Taï Forest ebolavirus
- Reston ebolavirus (causes monkey death and swine infection, not human; originated in the Philippines)
- Zaire, Bundibugyo, and Sudan ebolaviruses have all caused large outbreaks in Africa
- 6 Species
34
Q
*Ebolavirus Disease (EVD)
Epidemiology*
A
- First recognized in 1976
- One of 2 outbreaks that year occurred in a village near the Ebola River, hence its name
- Equatorial Africa
- Natural reservoir Pteropodidae fruit bats
- Able to infect humans, monkeys, chimpanzees, gorillas, baboons, and duikers; serologic evidence in domesticated dogs
- Spread through contact with infected animals, including human to human
35
Q
EVD Transmission Routes
A
- Zoonotic : Handling sick dead primates and fruit bats, including bushmeat
- Human: Exposure to blood body fluids
- Human to Human transmission causes
epidemics - Not an airborne pathogen
36
Q
Ebola Pathogenesis
A
- Infectious Dose = 1-10 virus particles
- Portal of entry: mucous membranes, breaks
in the skin, or parenterally - Migrates from the initial infection site to
regional lymph nodes and subsequently to
the liver, spleen, and adrenal gland - Causes immune system dysregulation and
cytokine storm - Disrupts cell adhesion molecules, leading to cell death, vascular, instability, and shock
- A rare, often fatal, viral hemorrhagic fever
37
Q
LRN U.S. Ebola tests
A
- FDA EUA real time RT PCR assays
- RNA ~detectable 3 10 days after symptom onset
- RNA is extracted following Trizol inactivation
- 2 CDC LRN Ebola Zaire RT qPCR assays (VP40 and NP):
- Whole blood, serum, plasma, urine
- EBOV testing requires prior approval from CDC
- CDC only:
- Virus isolation
- Serologic testing for IgM & IgG
- Tests for other pathogens
38
Q
EBOV is a Select Agent
A
- Extreme biohazard risk.
- Culturing specimens from Ebola PUIs must be done in a BSL4 (CDC)
- Handling specimens from suspected case may be done in BSL2 (Hospital or PHL)
- Recommended: Handle all original samples in BSL3 until inactivated
- A positive PCR result alone is not cause for select agent classification; EBOV nucleic acid does not fall under SA rules
- Specimens from a suspected Ebola patient are not covered by the Select Agent regulations, unless EBOV has been cultured from that patient
- Positive Ebola culture at CDC? Then all specimens from that patient fall under Select Agent rules
- Avoid/minimize aerosol generating
procedures - PPE: Coveralls with feet; Front closing
gown; Double gloves; PAPR
39
Q
EBV treatment
A
- Strict Isolation from other patients
- Supportive care rehydration improves survival
- Treating other infections if they occur
- Remdesivir, a viral polymerase inhibitor and one of the drugs used to treat COVID, was less effective than the mAb treatments
- Favipiravir, another pol inhibitor, may have cleared the virus from 2 male long term survivors (from detectable to undetectable by PCR in semen)
- Survivors: detectable levels of antibodies for 10 years
- rVSV ZEBOV Vaccine: Ervebo
- Live, attenuated recombinant vesicular stomatitis virus vaccine approved for use in adults (2019)
40
Q
West Nile Virus (WNV) General Characteristics
A
- Arboviruses
- ARthropod-BOrneVIRUSes
- Flaviviridae
- Zika
- St Louis encephalitis (SLE)
- Dengue
- TBE, Powassan
- Characteristics
- Spherical, enveloped
- Single-stranded, positive sense, non-segmented RNA
- First identified in Uganda, 1937
- The “West Nile fever” syndrome can differ among individuals
- IP: 2 to 15 days
- Common symptoms:
- Fever
- Headache
- Muscle pain or weakness
- Fatigue
- Other less common symptoms include rash, swollen lymph nodes, nausea, vomiting, eye pain
- Encephalitis
- 60-75% of WNV cases are encephalitis or meningoencephalitis Meningitis
- 25-35% of WNV cases are meningitis only
- Acute flaccid paralysis (AFP, AFM)
- Adult acute onset of asymmetric weakness in the absence of sensory loss
- Less common than meningitis or encephalitis
41
Q
West Nile Virus (WNV) Transmission
A
- MOSQUITO-CULEX
- Blood transfusion
- Organ transplant
- Anecdotal evidence of transplacental and breast milk transmission
- Birds are primary amplifier hosts
- Migratory birds can expand endemic region
- WNV isolated from numerous wild birds
- >200 bird species affected
- Ranges from no clinical signs in some species to over 90% fatality in others
42
Q
*West Nile Virus
Laboratory Diagnosis*
A
- Unexplained encephalitis or meningitis
- Onset during WNV “season”
- Location of exposure
- In CA: local activity
- Travel outside of CA: consider non-endemic arboviruses
- Confirmed:
- Isolation of virus from, or demonstration of specific viral antigen or nucleic acid in, tissue, CSF, blood, or other body fluid
- Four-fold or greater change in virus-specific quantitative antibody titers in paired sera,
- Virus-specific immunoglobulin M (IgM) antibodies in serum with confirmatory virus-specific neutralizing antibodies in the same or a later specimen
- Virus-specific IgM antibodies in CSF and a negative result for other IgM antibodies in CSF for arboviruses endemic to the region where exposure occurred.
- Probable:
- Virus-specific IgM antibodies in serum
- IgM EIA and IFA
-
IgG IFA
- Paired specimens only
- Plaque reduction neutralization test (PRNT)*
- WNV nAbtiter ≥4x SLEV nAbtiter
-
PCR
- CSF only
-
Neutralization
- Loss of viral infectivity through the reaction of virus with neutralizing antibody
- Highly specific*
-
Neutralization Functional assay
- Cell culture system with infectious virus
- Measure neutralizing antibody in patient serum/CSF
- MMR, YF, RFFIT, SC2
- ID specific arbo
- WNV vs SLE
- Zika vs DENV
43
Q
West Nile Virus (WNV) Vectors
A
-
Aedes aegypti
- “yellow fever mosquito”
- Aggressive, day biting
- Introduced 2013
- DENV, CHIKV, ZIKA, YF (WNV)
-
Aedes albopictus
- “Asian tiger mosquito”
- Aggressive, day biting
- Introduced 2011
- DENV, CHIKV (ZIKA, YF, WNV)
44
Q
Yellow Fever
A
-
Flavivirus
- Many historical outbreaks
- 1793, Philadelphia, PA: ~5000 deaths (10% pop.)
- 1853, New Orleans, LA: 7,849 deaths, delayed alerts
-
Vaccine-preventable
- Max Theiler, 1951 Nobel Prize
- Human and other primate reservoirs
- Vectorborne
- Aedes spp.
- Clinical syndromes
- Mild: Fever, headache, jaundice, nausea, vomiting, backache.
- Severe: High fever, jaundice, bleeding, shock, organ failure, 30-60% fatality in severe case-patients.
-
Testing:
- Acute infection: RT-PCR, paired IgG, IgM + PRNT (CDC)
- Immunity: PRNT (CDC)
- Immunocompromised, vaccine failures
- Vaccination history and detailed travel history (and more) required
45
Q
JEV( Japanese Enchapilitis Virus)
A
- Flavivirus
- Vectorborne
- Culex spp.
- Animal reservoirs (primarily pigs and wading birds)
- SE Asia, mostly rural
- Vaccine-preventable
- Ranges from asymptomatic to severe CNS, encephalitis
46
Q
Dengue Fever Virus
A
-
Flavivirus
- DENV-1, DENV-2, DENV-3, DENV-4 viruses
- Homotypic (type-specific) immunity
- Human and other primate reservoirs
- Vectorborne, bloodborne, maternal transmission
- Asymptomatic, dengue, severe dengue
- RT-PCR (including DENV-1-4), IgM + PRNT
- Case definition similar to WNV
- Symptomatic pregnant women tested for both Zika and DENV
- Confirmatory ZIKV-DENV PRNT
- Title 17 CCR §2505 laboratory reportable condition
- Symptoms
- ~80% asymptomatic
-
Dengue (dengue fever, break-bone fever)
- Nausea/vomiting, rash, myalgia/arthralgia, tourniquet test positive, leukopenia
-
Severe dengue (DHF, Dengue shock syndrome)
- Severe plasma leakage leading to shock or fluid accumulation with respiratory distress; severe bleeding; or severe organ impairment
- Increased risk of severe dengue in persons with previous dengue infections. May be associated with antibody-dependent enhancement at low, non-neutralizing Ab titers.
47
Q
Chikungunya Virus
A
-
Togaviridae> Alphavirus
- 1952, Tanzania
- Makonde: “that which bends up”
- Dec 2013, Western hemisphere
- Human and other primate reservoirs
- Vectorborne
- Mostly symptomatic: fever, arthralgia
-
RT-PCR, IgM + PRNT
- Case definition same as WNV
- Confirmatory CHIKV-WEE PRNT
- Title 17 CCR §2505 laboratory reportable condition
48
Q
Zika Virus
A
- Flavivirus
- Human and other primate reservoirs
-
Vectorborne, bloodborne, maternal, and sexual transmission
- Asx, sx, congenital neuro abnormalities, GBS
-
Nucleic acid testing (NAT), IgM + PRNT
- Case definition includes any detection of Zika nAb
- Title 17 CCR §2505 laboratory reportable condition
-
Symptoms
- ~80% asymptomatic
- Mostly mild febrile illness
- Rash
- Arthralgia
- Fever
- Conjunctivitis
- Congenital abnormalities
- CZS, IUGR, neurologic sequelae in children and adults
- Highest risk from infection in 1sttrimester
-
Congenital Zika Syndrome (CZS)
- Severe microcephaly where the skull has partially collapsed
- Decreased brain tissue with a specific pattern of brain damage
- Damage (i.e., scarring, pigment changes) to the back of the eye
- Joints with limited range of motion, such as clubfoot
- Too much muscle tone restricting body movement soon after birth
-
Guillain-Barrésyndrome (GBS)
- Rare, temporary post-infectious autoimmune disorder
- Muscle weakness, paralysis lasting weeks to months
59
Q
Hepatitis B Virus
A
- Hepatitis B virus (HBV) is a partially double-stranded DNA virus
- Hepadnaviridae family of viruses (genus Orthohepadnavirus)
- High
- blood
- serum
- wound exudates
- Moderate
- semen
- vaginal fluid
- saliva
- Low/Not Detectable
- urine
- feces
- sweat
- tears
- HBV Perinatal Transmission
- Transmission most likely during birth
- In absence of immunoprophylaxis: overall transmission rate of 5-90%
- MotherHBeAg-, (<10%) HBeAg+ (70-90%)
- Incubation period (days):
- Average 60-90
- Range 45-180
- Chronic infection:
- <5 yrs, 30%-90%!!
- ≥5 yrs, 2%-10%
- HBV Markers
- Anti HBs antibodies
- Immunity
- Anti HBc antibodies
- Exposure
- HBs Ag and/or HBV DNA
- Infection
- HBe Ag and/or HBV DNA
- Replication
- IgM anti HBc and/or HBV DNA
- Disease
- Anti HBs antibodies
- Vaccine
- Prevent perinatal HBV transmission
- Routine vaccination of all infants
- Vaccination of children in high-risk groups
- Vaccination of adolescents
- all unvaccinated children at 11-12 years of age
- “high-risk” adolescents at all ages
- Vaccination of adults in high-risk groups
65
Q
Pneumonia (lung inflammation)
A
- Inflammation from infection of one or both lungs
- Can be caused by >30 different infectious agents
- Critical to know the cause for effective treatment
- Role of laboratory
- Symptoms: cough, fever, chills, and trouble breathing
- (dyspnea); fatigue, sweats, headache, nausea, myalgia
- Alveoli become inflamed and fill with fluid and pus
- Decrease in O2 delivery throughout the body –> ARDS –>death
- Determine if Bacterial or Viral is imperative
66
Q
Overview of viral infections
A
