Type 3 and 4

• Type III - dsRNA

  • Reoviridae
• Type IV -(+) ssRNA

  • Astroviridae
  • Caliciviridae
  • Coronaviridae
  • Flaviviridae
  • Picornaviridae
  • Togaviridae
• Type III: Reoviridae

  • Rotavirus
  • Naked icosahedral dsDNA viruses: has two protein layers surrounding the capsid, wagon wheel-shaped under electron microscopy
  • Transmission and tropism: Fecal-oral route, replicates in the epithelial cells in the tips of the microvilli of the small intestine, shed in large quantities in the stool
• Type III: Reoviridae

  • Rotavirus
  • most common cause of infant and child gastroenteritis worldwide, winter diarrhea, symptoms generally occur suddenly include vomiting, diarrhea, fever, and abdominal pain and respiratory symptoms
• Type III: Reoviridae

  • Rotavirus (Diagnosis)
  • Can be detected only with special procedures: ELISA and agglutination test - viral antigens in feces, rapid membrane-bound colorimetric tests, electron microscopy of stool samples
  • vaccines - two types are currently available
  • infant viral gastroenteritis
• Type III: Reoviridae

  • Coltivirus
  • Arbovirus
  • Causative Agent of Colorado Tick fever
  • causes dengue-like infection in western US and canada
• Type III: Reoviridae

  • Orbivirus
  • Arbovirus
  • group of viruses that cause various disease in various vertebrae animals and humans
• Type IV: Astroviridae

  • Human Astroviruses
  • Naked icosahedral (+) ssRNA viruses: star-shaped under electron microscopy
  • Transmission: fecal-oral route
  • Causes gastroenteritis in: young children, elderly
• Type IV: Caliciviridae

  • Naked, icosahedral (+)ssRNA viruses
  • formerly a genus of picornaviridae and thus bear resemblance
  • Noroviruses (NoVs) - formerly known as Norwalk-like viruses under caliciviridae, most important cause of adult gastroenteritis, transmission: food-borne - most common, water-borne and person-to-person
  • most common cause of infectious gastroenteritis is US
  • Diagnosis: RT-PCR - most common diagnostic assay, electron microscopy, EIAs- stool samples, not sensitive enough
• Type IV: Caliciviridae

  • Naked, icosahedral (+)ssRNA viruses
  • formerly a genus of picornaviridae and thus bear resemblance
  • Sapoviruses (SaVs) - cup-shaped morphology, causes diarrhea and vomiting in infants, young children and elderly
  • Hepevirus - under hepatitis virus
• Type IV: Coronaviridae

  • Coronavirus - enveloped, icosahedral (+)ssRNA, has club-shaped projections on their surfaces; thus, the virions appear to be surrounded by halos
  • epidemiology and clinical manifestations: 15% cold-like (common cold) infections in adults, pediatric gastroenteritis - summer diarrhea
  • agents of severe respiratory tract infections: high fever, pneumonia, ARDS
• • SARS-CoV 1 (possible reservoir: horseshoe bats) - SARS
  • MERS-CoV (reservoir: dromedary camels) - MERS -enters human cells via DPP4/CD26
  • SARS-CoV 2 (possible reservoir: horseshoe bats) - COVID-19 -enters human cells via ACE2 receptor
• Type IV: Coronaviridae

  • Coronavirus (Diagnosis)
  • extremely fragile and therefore difficult to culture
  • can be directly detected using IF and EIA/ELISA
  • RT-PCR - most common, electron microscopy
  • SARS-CoV 1 antibodies can be detected using Western Blot
• Diagnosis for SARS-CoV 2

  • RT-PCR -serves as confirmatory test
  • antigen detection, serology/antibody detection
• Type IV: Flaviviridae

  • enveloped, icosahedral (+) ssRNA
  • has several important human pathogens, majority of which are zoonotic arboviruses
  • Japanese Encephalitis Virus - major cause of encephalitis in Asia, most common cause of arboviral encephalitis worldwide, considered an emerging pathogen, reservoir: pigs and wild birds; Vector: Culex mosquitoes, asymptomatic, flu-like illness to acute encephalitis
• Type IV: Flaviviridae

  • enveloped, icosahedral (+) ssRNA
  • has several important human pathogens, majority of which are zoonotic arboviruses
  • Dengue Virus - in tropical and subtropical during rainy season, former sylvatic cycles, vector: Aedes mosquitoes
  • Clinical Manifestation: Classic dengue fever (DF) aka breakbone fever, saddleback, mild and self-limiting: fever, headache, myalgia, bone pain, rash
  • Dengue hemorrhagic fever - more serious, classic DF + thrombocytopenia, hepatitis, hemorrhage, shock, fatal (~5% mortality)
  • Diagnosis - antigen detection, IgM and IgG, dengue duo combined Ag and Ab
• Type IV: Flaviviridae

  • enveloped, icosahedral (+) ssRNA
  • has several important human pathogens, majority of which are zoonotic arboviruses
  • Yellow Fever Virus
  • 3 cycles

  1. Sylvatic: monkey-to-monkey, usually in jungle areas
  2. Urban: human-to-human, usually in large towns and cities
  3. Intermediate: monkeys-to-humans, vv; common in small african villages

  Vector: Aedes mosquitoes
• Type IV: Flaviviridae

  • enveloped, icosahedral (+) ssRNA
  • has several important human pathogens, majority of which are zoonotic arboviruses
  • Yellow Fever Virus (Clinical Manifestations)
  • asymptomatic, yellow fever - acute infection, fever, myalgia, backache, headache, anorexia, nausea, and vomiting, where most recover after 4 days, 15% enter a systemic toxic phase where fever reappears, and patient develop jaundice, 50% mortality
• Type IV: Flaviviridae

  • enveloped, icosahedral (+) ssRNA
  • has several important human pathogens, majority of which are zoonotic arboviruses
  • St. Louis Encephalitis Virus - most common flavivirus in US, reservoir: birds; Vector: Culex mosquitoes
  • West Nile VIrus - reservoir: birds; vector: mosquitoes, human are dead-end hosts
• Type IV: Flaviviridae

  • enveloped, icosahedral (+) ssRNA
  • has several important human pathogens, majority of which are zoonotic arboviruses
  • Zika Virus - reservoir: birds, vector: mosquitoes, Zika fever: similar to other flaviviruses, associated with Guillan-Barre syndrome in adults, cause microcephaly and brain malformations
  • Hepacivirus - under hepatitis viruses
• Type IV: Picornaviridae

  • one of the largest families of viruses (in number)
  • structurally smallest RNA viruses (~30nm)
  • Clinically significant genera:

  -enterovirus

  -parechovirus

  -rhinovirus

  -hepatovirus
• Type IV: Picornaviridae

  • one of the largest families of viruses (in number)
  • structurally smallest RNA viruses (~30nm)
  • Enteroviruses - naked, icosahedral (+)ssRNA, polioviruses 1 to 3, coxsackieviruses A1 to A23, coxsackieviruses B1 to B6, enteroviruses 68 to 104 (HEV A, B, C, D), echoviruses 1 to 33
  • worldwide distribution
  • transmission: aerosol inhalation, fecal-oral route and fomites
  • portal of entry: alimentary canal via mouth
• Type IV: Picornaviridae

  • one of the largest families of viruses (in number)
  • structurally smallest RNA viruses (~30nm)
  • Enteroviruses (Clinical Manifestation)
  • develops in pharyngeal, and GI lymphoid tissue and spread to spinal cord, heart and skin
  • infections often cause mild nausea and diarrhea except neonates: aseptic meningitis, paralysis, sepsis-like, illness, myopericarditis, pleurodynia, conjunctivitis, exanthemas, pharyngitis, pneumonia, implicated early-onset diabetes, cardiomyopathy and fetal malformations
• Type IV: Picornaviridae

  • Enteroviruses (Diagnosis)
  • Culture: specimens early in disease is optimal, isolated from pharynx prior to onset of symptoms and for up to 1-2 weeks
  • Stool: up to 6 weeks after appearance of symptoms
  • Other: rectum, CSF, conjunctiva
  • Polioviruses, type B coxsackieviruses, echoviruses grow in: PMK, human fetal diploid fibroblast
  • Presumptive enterovirus ID: CPE - rounding necrosis, resistance to detergent, acid and solvents
  • Definitive ID: serum neutralization test - Lim-Benyesh-Melnick (LBM) Pools Neutralization Test
• Type IV: Picornaviridae

  • Enteroviruses - Poliovirus
  • 1% of cases infect the nervous system lead to paralytic poliomyelitis
  • Vaccines available: oral (live, attenuated) and IM (inactivated)
• Type IV: Picornaviridae

  • Enteroviruses - Coxsackie virus A
  • associated with common colds and herpangina
  • hand, foot, and mouth disease (HFMD): primarily caused by types A5, A10, A16, common enterovirus symptoms followed by simultaneous appearance of: small, painful sores on tongue, buccal mucosa and soft palate, maculopapular rash on hands, feet and buttocks, then bullae on soles and palms, transient rash
  • may be isolated from swabs of mouth and bullae
• Type IV: Picornaviridae

  • Enteroviruses - Coxsackie B virus
  • associated with common colds and pleurodynia/Bornholm disease
  • Enteroviruses - Echoviruses
  • enteric cytopathic human orphan virus
  • causes infantile diarrhea and aseptic meningitis
• Type IV: Picornaviridae

  • Parechoviruses
  • causes neonatal sepsis and meningitis, especially Human Parechovirus 3 (HPeV3)
• Type IV: Picornaviridae

  • Rhinoviruses
  • most common cause of colds
  • Culture: incubation at 33'C
  • CPE: refractile, round cell
• Type IV: Togaviridae

  • enveloped, icosahedral, (+)ssRNA
  • two clinically significant genera:

  -rubivirus

  -alphavirus
• Type IV: Togaviridae

  • enveloped, icosahedral, (+)ssRNA
  • Rubivirus - Rubella virus
  • Transmission: aerosol droplets - shed in nasopharyngeal and other secretions
  • rubella AKA German measles AKA third disease - asymptomatic, similar to rubeola/measles. mild fever + erythematosus maculopapular, discrete rash + post-auricular and sub-occipital lymphadenopathy, transient polyarthritis: common in adults
  • Congenital rubella syndrome - crosses the placenta and disseminate fetal tissues, lead to impaired infant, blueberry muffin baby
• Type IV: Togaviridae

  • enveloped, icosahedral, (+)ssRNA
  • Rubivirus - Rubella virus (Diagnosis)
  • Viral isolation: cumbersome, NPS/urine culture (33'C) PMK cells, CPE: syncytia; definitive ID by hemadsorption
  • Direct detection via IF or EIA recommended
  • Serology are effective as antibodies are presumed protective
  • Immunity is expected to be permanent after single infection or after vaccination (MMR)
• Type IV: Togaviridae

  • enveloped, icosahedral, (+)ssRNA
  • Alphaviruses
  • most are mosquito-borne and cause mild flu-like symptoms to encephalitis in humans and horses

  1. Eastern equine encephalitis (EEE) - reservoir: birds
  2. Western equine encephalitis (WEE) - milder than EEE
  3. Venezuelan equine encephalitis (VEE) - lower mortality than both EEE and WEE
  4. Chikungunya - difficult to clinically differentiate from dengue