Type 5 and 6

• Type V - (-)ssRNA

  • Arenaviridae
  • Bunyaviridae
  • Filoviridae
  • Orthomyxoviridae
  • Paramyxoviridae
  • Rhabdoviridae
• Type VI - ssRNA with DNA intermediate

  • Retroviridae
• Type V: Arenavirus

  • enveloped, complex, ambisense ssRNA viruses
  • rodent-borne viruses (reservoir: rodents) - zoonotic transmission: shed in rodent urine, feces and saliva, pet hamsters
  • ribosomes trapped in capsid because of sandy appearance (EM)
  • 29 named arenaviruses:

  1. Old World Complex: lymphocytic choriomeningitis (LCM) virus and Lassa viruses
  2. New World Complex: Junin virus (Argentinian HF), Machupo virus (Bolivian HF) and Guanarito virus (Venezuelan HF)
• Type V: Arenavirus

  • enveloped, complex, ambisense ssRNA viruses
  • LCM virus - causes flu-like illness, 25% may progress to meningitis
  • Lassa virus - causes lassa fever, come develop pleural effucions, hypotension, and hemorrhaging, CNS involvement: seizures and encephalopathy, 15% mortality
• Type V: Bunyaviridae

  • enveloped, helical, ambisense ssRNA viruses
  • Arboviruses of Bunyaviridae
  • usually asymptomatic but may cause a febrile illness, hemorrhagic fever, encephalitis
  • includes:

  1. Phlebovirus - Rift Valley fever virus: encephalitis and hepatitis
  2. Orthobunyavirus - LaCrosse virus (LACV) and California encephalitis virus: encephalitis
  3. Nairovirus - Crimean-Congo hemorrhagic fever (CCHF) virus: vascular endothelium and liver
• Type V: Bunyaviridae

  • enveloped, helical, ambisense ssRNA viruses
  • Hantavirus
  • rodent-borne viruses
  • Hantaan virus, Seoul virus, Puumala virus, and Dobrava virus
  • causes hemorrhagic fever with renal syndrome (HFRS) AKA Korean hemorrhagic fever
  • Puumala virus - causes a mild form (nephropathica epidemica)
  • Sin Nombre virus (SNV) - causes hantavirus pulmonary syndrome (HPS)
• Type V: Filoviridae

  • enveloped, complex (-) ssRNA viruses
  • includes:

  1. Marburgviruses - Lake Victoria Marburgvirus
  2. Ebolavirus: Zaire (ZEBOV/EBO-Z), Sudan (SEBOV/EBO-S), Reston (REBOV/EBO-R), Ivory Coast (ICEBOV), Bundibugyo (BEBOV)

  • Characteristics: rarely cause human infection (Lake Victoria Marburgvirus hemorrhagic fever or Ebola HF) results from contact with infected monkeys, high mortality rate
  • unknown reservoir in nature
• Type V: Orthomyxoviridae

  • enveloped, helical (-) ssRNA viruses
  • AKA influenza viruses, matrix protein (M) and nucleoprotein (NP): structural proteins where three genera classification was based:

  -influenzavirus A

  -influenzavirus B

  -influenzavirus C

  • hemagglutinin (H or HA) and neuraminidase (N or NA): surface glycoproteins that distinguishes the subtypes of influenzavirues A
  • worldwide
  • zoonotic origin: birds and mammals
  • flu season: November to April (north); May to October (south)
• Type V: Orthomyxoviridae

  • antigenic variation: antigenic drift (causes epidemics), antigenic shift (causes pandemics)
  • antigenic drift - minor antigenic structure change due to accumulated mutations, occur with all three types of influenza (A,B,C)
  • antigenic shift - drastic/major change resulting to a new H or N antigen, two mechanisms:

  1. genetic reassortment - mixture of different influenzavirus, primarily occur in pigs
  2. adaptive mutation - novel strains slowly mutate and becomes transmissible

  • commonly occurs with influenza A
• Type V: Orthomyxoviridae

  • antigenic variation
  • influenza in the 20th century and beyond
  • three major antigenic shifts:

  1. 1918: Influenza A (H1N1) AKA Spanish flu
  2. 1957: Influenza A (H2N2) AKA Asian flu
  3. 1968: Influenza A (H3N2) AKA Hongkong flu

  • predominant strain since 1977: H1N1 and H3N2
  • 1998, 2004, 2005: outbreaks of influenza A (H5N1)
  • 2009: Influenza A (H1N1) AKA swine flu
• Type V: Orthomyxoviridae

  • Transmission: aerosol inhalation
  • clinical manifestations - asymptomatic
  • influenza or flu
  • usually ill for 7 days; may need 2 weeks for convalescence
  • Complications include secondary bacterial pneumonia and Reye's syndrome
• Type V: Orthomyxoviridae

  • Diagnosis
  • Optimal specimen: nasopharyngeal swabs, washes or aspirates collected early in the disease
  • direct detection via DFA, EIA, optical immunoassays
  • commercial rapid kits are available
  • Culture: incubation at 33'C - grows in amniotic cavity, positive culture adsorb RBC's, rapid culture assays make use of IF staining
  • RT-PCR most common
  • Vaccine: Trivalent - 2A strains and 1B strain, as recommended by CBC, WHO, yearly doses
• Type V: Paramyxoviridae

  • Respiratory Syncytial Virus (RSV)
  • Transmission: large-particle droplets and fomites
  • clinical manifestation: causes croup, bronchitis, bronchiolitis, interstitial pneumonia
  • most common cause of severe LRT (bronchiolitis)
  • pneumonia is most common manifestation in older adults
• Type V: Paramyxoviridae

  • Respiratory Syncytial Virus (RSV)
  • Diagnosis
  • Cultures: difficult due to fragility
  • grows best in continuous epithelial cell lines, also grow in PMK and human diploid fetal cells, CPE: syncytia, definitive ID: IF, EIA, serum neutralization test
  • molecular methods not standardized
  • no vaccine
• Type V: Paramyxoviridae

  • Human Metapneumovirus (hMPV)
  • Relatively the most novel of the clinically significant viruses in Paramyxoviridae
  • Clinical manifestations: similar to influenza virus, RSV, PIV
  • Mild URTI to acute LRTI symptoms: fever, nonproductive cough, sore throat, wheezing, congestion, shortness of breath, lethargy
  • infection occur in children
• Type V: Rhabdoviridae

  • enveloped, helical, (-) ssRNA viruses
  • rhabdos means rod; bullet-shaped virions
  • Rabies Virus
  • transmission: primarily through bite or scratch by rabid animals, may be transmitted organ transplantation
  • clinical manifestations: rabies (acute, fulminant, fetal encephalitis) -pain at exposure site and vague flu-like, cannot be successfully treated once symptoms appear
  • prevention: postexposure prophylaxis which includes vigorous cleaning of wound right away and immunization (ERIG or HRIG + three-injection series of rabies vaccine)
• Type V: Rhabdoviridae

  • enveloped, helical, (-) ssRNA viruses
  • Rabies Virus (Diagnosis)
  • generally involves determining whether animal that bit a huma has rabies: animal is killed and head is sent to reference laboratory, direct IF or DFA - fastest and most sensitive method (gold standard) for rabies virus ID
  • Histology: uses Seller stain to demonstrate Negri bodies, animal head - impression smears from various parts, live patients: skin biopsies especially at hairline at back of neck and cornea impression
• Type VI: Retroviridae

  • enveloped, icosahedral, (+) ssRNA viruses
  • RNA-dependent DNA polymerase (reverse transcriptase)
  • Human T-lymphotropic Viruses (HTLV)
  • HTLV-1, 2 and 5
  • associated with several leukemias, sarcomas, lymphomas
• Type VI: Retroviridae

  • enveloped, icosahedral, (+) ssRNA viruses
  • Human Immunodeficiency Virus (HIV)
  • 2 types: HIV-1 (worldwide), HIV-2 (west africa)
  • causative agent of AIDS
  • Primary target cells: T helper cells (CD4), monocytes/macrophages
• Type VI: Retroviridae

  • enveloped, icosahedral, (+) ssRNA viruses
  • Human Immunodeficiency Virus (HIV)
  • transmission: blood and exchange of other body fluids
  • low viral levels in plasma, saliva, tears, urine and milk
  • not highly contagious: normal, social, nonsexual contact
  • high risk: unprotected sex, multiple sex partners, IV drug abuse, receiving blood and bld products, babies to mothers (+)
  • highest risk: ulcerative STI
  • Sexual Contact (88%): Heterosexual contact (27%); MSM (61%)
• Type VI: Retroviridae

  • enveloped, icosahedral, (+) ssRNA viruses
  • Human Immunodeficiency Virus (HIV)
  • Clinical Manifestations
  • Phases - initial/acute infections: mild, resemble IM or flu
  • clinical latency (rapid replication in lymphoid tissue but not present in bloodstream)
  • AIDS-related complex
  • AIDS: lymphopenia, CD4+ T cells
  • can cause encephalitis and dementia
• Type VI: Retroviridae

  • enveloped, icosahedral, (+) ssRNA viruses
  • Human Immunodeficiency Virus (HIV)
  • Diagnosis
  • generally based on demonstration of anti-HIV antibodies
  • screening tests: different methods including EIA and IF

  1. first-generation - use purified viral lysate as antigens
  2. second-generation - use recombinant viral proteins
  3. third-generation - double-antigen sandwich assay
  4. fourth-generation - detects both HIV antigen and antibodies

  • rapid assays using serum
  • confirmatory: western blot (primary confirmatory test)- detects p24, p31, gp41, and gp120/160
  • IF
• Type VI: Retroviridae

  • enveloped, icosahedral, (+) ssRNA viruses
  • Human Immunodeficiency Virus (HIV)
  • Diagnosis
  • some cases require detection of viral antigen or RNA - used in neonates, HIV viral load (RNA) assays - prediction of therapeutic efficacy
  • Treatment: highly active antiretroviral therapy (HAART)
  • done immediately after diagnosis, does not cure the disease, only controls it
  • antiviral drugs used: Nucleoside analogue reverse transcriptase inhibitors (NRTIs), Non-Nucleoside analogue reverse transcriptase inhibitors (NNRTIs), protease inhibitors, fusion inhibitors
• Type V: Paramyxoviridae

  • enveloped, helical (-) ssRNA
  • largest RNA virus
  • Culture: 33'C
  • Parainfluenza viruses (PIVs)
  • four types (1-4) cause disease in humans
  • 2 surface antigens/proteins:

  1. hemagglutinin-neuraminidase (HN) antigen
  2. fusion (F) antigen
• Type V: Paramyxoviridae

  • Transmission: respiratory secretions, aerosol inhalation and direct contact
  • Clinical manifestations
  • PIV-1, PIV-2 - most serious illnesses: children 2-4 years of age
  • PIV-1 - primary cause of croup
  • PIV-3 - bronchiolitis and pneumonia in infants (second in importance after RSV)
  • PIV-4 - milder URTI
  • other: rhinitis/common colds, pharyngitis, laryngotracheitis, tracheobronchitis