Things to Remember about RNA Viruses
- All RNA viruses are ssRNA except REO is dsRNA
- All RNA viruses replicate in the cytoplasm except (ORB) ORTHOMYXO, RETRO, and BORNA replicate in the nucleus
- 3 RNA viruses are non enveloped (PCR), (PCR = PICORNA, CALICI –Noro-, REO)
- 5 RNA viruses have icosahedral symmetry (PCR + FT), (PCR = PICORNA, CALICI, REO) (FT = FLAVI, TOGA)
Below is a summary of RNA virus families based on criteria for classification and their properties. The details for each RNA virus family will be covered on separate topics.
EXTENSIVE SUMMARY OF RNA VIRUSES
| Family name | Rhabdoviridae | Retroviridae | Orthomyxoviridae | Paramyxoviridae | Picornaviridae | Bunyaviridae | Reoviridae | Birnaviridae | Calciviridae |
| Genome | ss linear RNA, (-) sense | Two copies ss linear RNA, (+) sense | ss linear RNA, (-) sense, 8 segments | ss linear RNA, (-) sense | ss linear RNA, (+) sense | ss linear RNA, (-) sense, 3 segments | ds linear RNA, (+/-) sense, 10-12 segments | ds linear RNA, 2 segments | ss RNA, (+) sense |
| Genome size | 13-16 kb | 3.5-9 kb | 13.6 kb | 16-20 kb | 7.2-8.4 kb | 13.5-21 kb | 22-27 kbp | 7 kbp | 8 kb |
| Symmetry of capsids | Helical | Icosahedral | Helical | Helical | Icosahedral | Icosahedral | Icosahedral | Icosahedral | Icosahedral |
| Naked or enveloped | Enveloped | Enveloped | Enveloped | Enveloped | Naked | Enveloped | Naked | Naked | Naked |
| Baltimore class | V | VI | V | V | IV | V | III | III | IV |
| Baltimore class III: dsRNA: Have segmented genomes which are transcribed separately to mRNA by viral RNA dependent RNA polymerase packaged within their virions | Baltimore class IV: ss (+) RNA viruses: The genome serves directly as mRNA which is translated into early viral proteins used for replicating the viral genome
Ss (+) RNA → mRNA |
Baltimore class V: ss (-) RNA: Must synthesize (replication) a complementary + strand which serves as mRNA. Have to carry RNA-dependent RNA polymerase
Ss (-) RNA →cRNA mRNA |
Baltimore class VI: ss (+) RNA: Genomes are (+) sense RNA but unique in that they are diploid and they do not serve directly as mRNA, but as a template for reverse transcription into DNA. DNA integrated into host DNA (Provirus)
RNA DNA RNA |
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| Virion | 70-85 x 130-380 nm | 80-130 nm | 90-120 nm | 150-300 nm | 28-30 nm | 90-120 nm | 6-80 nm | 60 nm | 35-40 nm |
| Virion polymerase | + | + | + | + | – | + | + | + | – |
| Genus and species | Lyssavirus:
Rabies virus Vesiculovirus: VSV-Indiana VSV-New Jersey Ephemerovirus Bovine ephemeral fever virus |
Alpharetrovirus:
-ALV, RSV Betaretrovirus: Jaagsiekte sheep retrovirus Gammaretrovirus FeLV Deltaretrovirus BLV, HTLV Lentivirus HIV1, HIV2, FIV, EIAV,CAEV, |
Influenzavirus A
Avian influenza Equine influenza Swine influenza Human influenza Influenzavirus B Human influenza Influenzavirus C Human influenza |
Paramyxovirinae
Rubulavirus MuV, PIV 5, hPIV2/4a/4b Avulavirus hPIV1/3, bPIV3 Morbillivirus Pneumovirinae Pneumovirus hRSV, bRSV Metapneumovirus hMPV, aMPV |
Enterovirus
Human enterovirus A, B, C&D, Bovine enterovirus, Porcine enterovirus A&B, Human rhinovirus A&B, Aphthovirus FMDV, Equine rhinitis A virus |
Bunyavirus
LaCrosse encephalitis virus Phlebovirus RVFV Nairovirus CCHFV, NSDV Hantavirus Hemorrhagic Fever with Renal Syndrome Hantavirus Pulmonary Syndrome
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Orthoreoviruses:
Mammalian reoviruses type 1, 2, 3 Avian reoviruses Rotaviruses Rotavirus A, B, C, D, E, F Orbiviruses: AHSV, BTV Changuinola virus Coltiviruses: Colorado tick fever virus |
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| Disease | Rabies is caused by the rabies virus | AIDS is caused by HIV1 and HIV2 | Influenza A caused by influenza A viruses | Newcastle disease caused by NDV | FMD caused by FMDV | RVF caused by RVFV | BT caused by BTV | ||
| Hosts | All warm-blooded animals | Human | Birds, Horse, Pigs, human | Avian species | cloven-hoofed animals | Cattle, goats, sheep, man | Cattle, Sheep, goats | ||
| Clinical signs | Fever (39-40) hydrophobia: pharyngeal muscle cramp, dyspnea
dehydration Paralytic stage(15-20hs) – nerve fiber paralysis respiratory and circulatory failure death |
Asymptomatic phase 2-15 years (avg. 10)
HIV destroys the immune system When T4 cell levels fall below 200/mL, AIDS symptoms appear including fever, swollen lymph nodes, diarrhea, weight loss, neurological symptoms, opportunistic infections, and cancers |
Fever, headache, cough, sore throat, nasal congestion, sneezing, and body aches |
Ocular and/or nasal discharge, dyspnoea, and bloody diarrhea. Central nervous system signs can also occur, including depression or the opposite-hyperexcitability; vestibular or balance problems; tremors, especially of the head and neck; weakness; and partial or total paralysis | Blisters inside the mouth that lead to excessive secretion of stringy or foamy saliva and to drooling, and blisters on the feet that may rupture and cause lameness. weight loss no recovery for several months, milk production can decline significantly | In animals: Storm abortions, high mortality, high fever, lymphadenitis, nasal and lachrymal discharges, severe prostration, dystocia,
In humans severe influenza-like illness characterized by fever (37.8–40 °C), headache, muscular pain, vomiting, and extreme weight loss |
Fever, frothing at mouth, shock, coronitis |
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| Laboratory diagnosis | -Antigen detection (IF),
-Negri bodies -Isolation -RT-PCR
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ELISA, latex agglutination, and rapid antibody tests Western blot analysis and RT-PCR to rule out false +ves, 2nd tests for –ves (3-6 months later) | Antigen detection (ELISA, HI, CF and VNT), Antibody detection (IF),
RT-PCR
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Virus isolation, ELISA, HI, CF, VNT, RT-PCR |
Virus isolation, ELISA, CF, RT-PCR | Virus isolation, ELISA, CF, VNT, RT-PCR | Virus isolation, IF, Serologic assays (ELISA, latex agglutination)
RT-PCR |
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| Target cells |
Neuronal cells |
CD4 cells and macrophages with CD4 | Epithelial cells | Epithelial cells | Epithelial cells | Hepatic cells, | Intestinal epithelial cells | ||
| Cellular Virus receptors |
CD56, p75NTR |
CD4, CCR5, and CXCR4 |
Sialic acids; N-acetylneuraminic acid | sialic acid | Heparan sulfate, Glycosaminoglycan | Cell receptors | Sialic acid | ||
| Viral attachment ligand |
RABV G protein |
gp120 |
hemagglutinin | hemagglutinin | Capsid proteins | Gn and Gc proteins | σ1, JAM-A | ||
| Virus replication | Entry via endocytosis, pH-dependent, replication in the cytoplasm, virus assembly by budding from the host plasma membrane | Entry via fusion with the cell membrane, pH-dependent, replication, provirus integrates into the host genome in the nucleus | Entry via receptor-mediated endocytosis, pH-dependent, replication in the nucleus, assemble in the membrane, release by budding | Entry via receptor-mediated endocytosis, pH-dependent, replication in the cytoplasm, assemble in the membrane, release by budding | Entry via the receptor, replication in the cytoplasm | Entry via receptor-mediated endocytosis, pH-dependent, replication in the cytoplasm, release by budding at Golgi or cell membrane | Entry via receptor mediated endocytosis, Acid pH, Proteolytic processing of outer capsid, replication in cytoplasm, exit by lysis | ||
| Transmission | A bite from a rabid animal | Sexual intercourse | Airborne (Inhalation) | Direct contact | Contact animal to animal, aerosol and fomites | Mosquitos bite, eating infected animals | Culicoides | ||
| Reservoir host | -Wild animals | – | Wild aquatic birds, humans, animals | – | – | ??? | |||
| Vector | wild animals and unvaccinated dogs & cats | – | – | – | – | Mosquitoes | |||
| Control | Vaccination (cats, dogs, and personnel at risk)
Post-exposure prophylaxis in humans |
No vaccine, no cure; therapies slow down the progress of the disease or diminish the symptoms | Inactivated virus vaccine, Subunit vaccine, Live, attenuated influenza virus vaccines, Antiviral drugs | Hygiene
An inactivated viral vaccine is available |
Vaccines are available with no cross-protection
Palliative treatment |
Inactivated vaccines are available | |||
VSV=vesicular stomatitis virus; RSV=Rous sarcoma in chicken; ALV=Avian Leukosis virus; FeLV=Feline leukaemia virus, BLV=Bovine leukaemia virus; HTLV=Human T Cell Leukaemia, HIV=Human immunodeficiency virus, EIAV=Equine infectious anaemia virus; FIV=Feline immunodeficiency virus; CAEV=Caprine arthritis encephalitis virus; AIDS=Acquired immunodeficiency syndrome; MuV=Mumps virus; PIV5=Parainfluenza virus 5 (canine); hPIV2/4a/4b=Human parainfluenza virus type 2, type 4a and 4b; NDV=Newcastle disease virus (avian paramyxovirus 1); hPIV1/3=Human parainfluenza virus type 1 and type 3; bPIV3=Bovine parainfluenza virus type 3; MeV=Measles virus; CDV=Canine distemper virus; PPRV=Peste-des-petits-ruminants virus; RPV=Rinderpest virus; hRSV=Human respiratory syncytial virus A2, B1, S2; bRSV=Bovine respiratory syncytial virus; hMPV=Human metapneumovirus; aMPV=Avian metapneumovirus, FMDV=Foot and mouth Disease virus, RVFV=Rift Valley fever virus; CCHFV=Cremian-Congo Haemorrhagic fever virus; NSDV=Nairobi sheep disease virus; AHSV=African Horse sickness virus; BTV=Blue tongue virus
| Family name | Flaviviridae | Togaviridae | Coronaviridae | Filoviridae | Arenaviridae | Astroviridae | Arteriviridae | Toroviridae | Bornaviridae |
| Genome | ss linear RNA, (+) sense | ss linear RNA, (+) sense | ss linear RNA, (+) sense | ss linear RNA, (-) sense | ss linear RNA, (-) sense, 2 segments | ss linear RNA, ( ) | ss RNA, (+) | ss RNA, (-) sense | |
| Genome size | 10 kb | 12 kb | 16-21 kb | 12.7 kb | 10-14 kb | 12.7-15.7 kb | 8.9 kb | ||
| Symmetry of capsids | Icosahedral | Icosahedral | Helical | Helical | Helical | Icosahedral | |||
| Naked or enveloped | Enveloped | Enveloped | Enveloped | Enveloped | Enveloped | Enveloped | |||
| Baltimore class | IV | IV | IV | V | V | ||||
| Virion | 40-50 nm | 60-70 nm | 80-160 nm | 80 x 7790-14,000 nm | 50-300 nm | 28-30 nm | 40-60 nm | + | |
| Virion polymerase | – | – | – | + | + | – | |||
| Genus and species | Flavivirus
Dengue viruses 1&2, YFV, JEV, WNEV, SLEV, TBEV Hepaciviruses Hepatitis C virus Pestiviruses BVDV 1&2, BDV, HCV |
Alphavirus
VEEV, EEEV, WEEV Chikungunya virus Rubivirus Rubella virus
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equine arteritis virus (EAV),
porcine reproductive and respiratory syndrome virus (PRRSV)
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| Disease | BVD caused by BVDV | ||||||||
| Hosts | Bovine, Camelids, deer | ||||||||
| Clinical signs | Mild fever, decreased milk production, ulcerative stomatitis, diarrhea, respiratory distress, embryonic death, abortions, birth defects,
persistently infected calves |
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| Laboratory diagnosis | Virus isolation, ELISA, VNT, IF, RT-PCR | ||||||||
| Target cells | |||||||||
| Cellular Virus receptors | |||||||||
| Viral attachment ligand | |||||||||
| Virus replication | Clathrin-mediated endocytosis, low pH, replicate in the cytoplasm, assemble on ER | ||||||||
| Transmission | |||||||||
| Reservoir host | |||||||||
| Vector | |||||||||
| Control | Inactivated or attenuated vaccines are available
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VEEV=Venezuelan equine encephalitis virus; EEEV=Eastern equine encephalitis virus; WEEV=Western equine encephalitis virus; BVDV=Bovine viral diarrhea virus; BD= Border disease virus; HCV=Hog cholera virus; YFV=Yellow fever virus; JEV=Japanese Encephalitis virus; WNEV=West Nile encephalitis virus; SLEV=St. Louis encephalitis virus; TBEV=Tick-borne encephalitis virus;