Mycology Virology 311

• Caliciviridae


  • First Described in 1976
  • Genome: ssRNA
  • Naked (nonenveloped)
  • Capsid: 30-45nm, Icosahedral
  • Has 32 cup-shaped depressions
  • "calici" - chalice or calyx, cup-like
  • Describe as the "STAR OF DAVID"
• Human caliciviruses (HuCV)


  Most common in infecting humans
• Small, round-structured viruses (SRSV)

  Norwalk virus: a very important pathogen which is under the caliciviridae
• Mode of Transmission (MOT)

  Fecal Oral Route (FOR) through ingestion
• Enterititis


  • "WINTER VOMITING DISEASE"
  • Outbreaks commonly happen during winter
• Calicivirus is the most common virus infecting children under 4 years old
• Calicivirus infection


  • Incubation period: 12 hours to 4 days
  • Most infections are asymptomatic
  • Mild diarrhea, vomiting anorexia and fever
  • 1/3 have respiratory symptoms
• Diagnosis of Calicivirus


  • ELISA
  • EM
  • Antigen assay: uses Serum
• Astroviridae


  • Described in relation to an outbreak of gastroenteritis in 1975
  • Small ssRNA, naked
  • Capsid: 27-32mm, Icosahedral
  • Round with unbroken surface
  • Appearance: "5 or 6 pointed scar"
  • Immunologically distinct from Norwalk and Caliciviruses
• Astrovirus infection


  • Low level of Pathogenicity
  • Diarrhea
  • Headache
  • Nausea
  • Low grade fever
  • Vomiting
• Mode of Transmission (MOT) for Astrovirus


  Fecal Oral Route (FOR)
• Diagnosis of Astrovirus


  • EM (Electron Microscopy)
  • IFT (Immunofluorescence Test)
• Bunyaviridae


  • Spherical or oval-shaped
  • Enveloped RNA viruses
  • More than 30 different Hantavirus species
• Hantavirus survival


  • Survive 12 hours at 4C and high salt conc.
  • Survive 1-3 days after drying at non-physiological pH
• Hantavirus transmission


  • Via chronically infected rodent
  • Horizontal transmission by intraspecific aggressive behavior
• Hantavirus transmission routes


  • Aerosolized excreta
  • Throat swab and feces
  • Mucous membrane contact
  • Skin breaches
• Hantavirus in rodents


  • Do not adversely affect their host
  • Host will acquire life-long chronic infection
  • Infectious virus is shed through saliva, urine and fecal matter
  • Humans infected by inhaling aerosols produced while host is excreting waste
  • Aerosols can occur by disturbing contaminated nesting materials
• Hantavirus transmission vectors


  • Deer mouse (Peromyscus maniculatus)
  • Cotton rat (sigmodon hispidus)
  • White-footed mouse (Peromyscus leucopus)
  • Striped filed mours (Apodemus agrarius)
  • Bank vole (Clethrionomys glareolus)
  • Rat (Rattus)
• Hantavirus Disease


  • Hantavirus antigen become disseminated throughout the bloodstream, causing Viremia
  • Loss of fluid from blood vessels
• Hantavirus Diseases


  • Hemorrhagic Fever with Renal syndrome (HFRS)
  • Hanta virus pulmonary Disease (HPS)
• Stages of Hemorrhagic Fever with Renal Syndrome (HFRS)

  1. Febrile phase

  2. Hypotensive phase

  3. Oliguric phase

  4. Diuretic phase

  5. Convalescent phase
• Febrile Phase of HFRS

  • Persist for 3-5 days
  • Sudden onset fever and chills (flu-like symptoms)
  • Headache, severe myalgia, nausea, blurred vision, photophobia, pain on ocular movement
  • Flushing of face
  • Petechiae
  • Abdominal pain and back pain
  • "Vascular leak syndrome": characterized by thirst, edema, hemoconcentration, postural hypotension
• Hypotensive Phase of HFRS

  • Lasts for hours or 1-2 days
  • Blood pressure decrease, hypovolemia, shock
  • Worsening of bleeding manifestations: petechiae, epistaxis, gastrointestinal and intracranial bleeding
  • Levels of Urea and Creatine in blood rise
  • Proteinuria (presence of protein in urine)
• Oliguric Phase of HFRS


  • Lasts for 3-7 days
  • Elevation of blood pressure
  • Hypervolemia leading to hypertension
  • Urine output decreases
  • Blood electrolyte imbalance
  • Continuation of hemorrhagic symptoms
  • Severe complications: cardiac failure, pulmonary edema, cerebral bleeding
  • 50% of fatalities during this phase
• Nephropathia Epidemica (NE)


  • Cause: Puumula strain
  • Most common form of HRS in Europe
  • Milder form of HFRS
  • Similar sequence of symptoms, but attenuated
  • Only 6% of serologically conformed cases require hospitalization
• Stages of Hanta Pulmonary Syndrome

  1. Febrile phase

  2. Cardiopulmonary phase

  3. Diuretic phase

  4. Convalescent phase
• Febrile Phase of Hanta Pulmonary Syndrome

  • Lasts 3-5 days (1-12 days)
  • Fever, myalgias, malaise
  • Headache, dizziness, anorexia, nausea, vomiting and diarrhea
  • Difficult to diagnose at this stage
• Cardiopulmonary Phase of Hanta Pulmonary Syndrome


  • Non-productive cough and tachypnea (rapid breathing) appear
  • Presentation and rapid progression of shock and pulmonary edema (4-24h)
  • Hypovolemia due to progressive leakage of high protein fluid from blood to lung interstitium and alveoli
  • Myocardial failure
  • Hypotension and oliguria (urine decreases)
  • Death within 24-48 hours due to hypoxia and circulatory compromise
• Diuretic Phase of Hanta Pulmonary Syndrome

  • Rapid clearance of pulmonary edema
  • Resolution of fever and shock
  • Early sign: spontaneous diuresis
• Convalescent Phase of Hanta Pulmonary Syndrome

  • Up to 2 months
  • Slow but full recovery
  • Short term finding: Pulmonary dysfunction
  • Decreased small-airways flow and diminished diffusing capacity
• Clinical Laboratory Findings for Hantavirus

  • Thrombocytopenia
  • Normal or elevated WBC on presentation of symptoms which increases to high values as disease progresses
  • Presence of immunoblasts from late in febrile phase
  • Hemoconcentration
  • Radiologic findings show progression from slight interstitial edema to bilateral alveolar edema
• Etiological diagnosis of Hantavirus

  • Serologic: ELISA IgM capture assay, Western blot, Indirect IFT, Rapid immunoblot strip assay
  • Immunohistochemistry: can test formalin fixed tissue with specific monoclonal and polyclonal antibodies
  • RT-PCR: demonstration of hanta virus antigen in tissues by immunochemistry
• Problems diagnosing Hantavirus


  • Symptoms is confused with Influenza
  • Common signs of URTI such as sore throat, sinusitis, ear pain
  • Abdominal pain misinterpreted as appendicitis
• Treatment for Hantavirus


  • No CURE
  • Prompt diagnosis and good management of illness is effective in improving patient's survival
  • Aggressive supportive care: Fluid management, Hemodynamic monitoring, Ventilatory support, Peritoneal dialysis, Pressor agents, Inotropic agents
  • Ribavirin administered intravenously is effective against HFRS but not HPS
  • Extra Corporeal Membrane Oxygenation (ECMO) removes blood from the body and artificially removes CO2 and adds O2, but is costly and difficult to perform
• Prevention and Control of Hantavirus

  • Vaccines: Naked DNA, Recombinant non-pathogenic virus, Rodent-brain derived, Cell cultured derived, Inactivated virus
  • Hygiene: Prevent aerosolization of virus from rodent excrement, Dampen surfaces with bleach before cleaning, Control rodents and human contact with rodents
  • Vector Control
• Arenaviridae


  • Spherical to pleomorphic, 50-300 nm, "spiked" enveloped from the plasma membrane, Inner structure that appears to be granulated
  • LCM virus: Europe and America
  • Lassa virus: Africa
  • Junin and Machupo viruses: South America
• Arenaviridae Pathogenesis


  • Source: Rodents
  • MOT: per os - "through mouth or ingestion", Aerogenic, Skin contact
  • LCM: Harmless and flu-like, Can infect the CNS, Meningitis and Encephalitis
  • Lassa: Pantotropic, Hemorrhagic Fever affecting all inner organs
  • Junin and Machupo: CNS involvement is frequent, Lethality is lower than the other two viruses (LCM & Lassa)
• Diagnosis of Arenaviridae


  • Isolated from blood
  • Postmortem isolation (after death): liver tissue
• Transmission


  • Via chronically infected rodent
  • Horizontal transmission of infection by intraspecific aggressive behavior
• Horizontal means that virus may be present in the feces of rodents, which we can inhale once aerosolized