Single-Stranded RNA Viruses Overview

Single-Stranded RNA Viruses

• Groups: Arenaviridae, Bunyaviridae, Caliciviridae, Coronaviridae, Filoviridae, Flaviviridae, Orthomyxoviridae, Paramyxoviridae, Picornaviridae, Retroviridae, Rhabdoviridae, Togaviridae
• Examples: Lassa virus, Sin Nombre virus, Norovirus, Coronaviruses, SARS, Ebola virus, Dengue virus, Influenza A, B, C, Parainfluenza viruses, Mumps virus, Enteroviruses, HIV, Lyssaviruses, Eastern Equine Encephalitis virus, Western EE virus, Rubella virus, Hepatitis viruses (HAV, HAB, HAC, HAD, HAE)

Arenaviruses

• Name: From Latin, meaning "sand"
• Appearance: Sandy and granular under electron microscope
• Transmission: Contact with aerosolized virus or fomites from infected rodents.
• Example: Lassa Virus
• Symptoms: Asymptomatic infection is common, some develop fever, headache, pharyngitis, myalgia, diarrhea, vomiting, pleural effusion, hypotension, and hemorrhaging.
• Detection: ELISA to detect IgM and IgG antibodies
• Treatment: Ribavirin if started within 6 days of exposure

Bunyaviridae

• Transmission: Arthropod feeding on blood of vertebrate hosts
• Symptoms: Asymptomatic viremia, fever, hemorrhagic fever, or encephalitis
• Example: Rift Valley fever virus (RVF)
• Other: Encephalitis, hepatitis (targets brain and liver), and other illnesses

Noroviruses (NoVs)

• Transmission: Foodborne, waterborne, and person-to-person contact
• Symptoms: Severe nausea, vomiting, diarrhea, and low-grade fever
• Infectious rates: High, as high as 50%
• Incubation: 12-72 hours

Bunyaviridae Sin Nombre Virus

• Causative Agent: Hantavirus Pulmonary Syndrome
• Transmission: Inhalation of contaminated aerosolized rodent excretions.
• Clinical Manifestations: Febrile prodrome (fever, chills, and myalgia), followed by hypertensive shock and pulmonary edema

Sapovirus (SaVs)

• Causes: Diarrhea and vomiting in infants, young children, and older patients
• Detection: Electron microscopy, molecular methods (e.g. RT-PCR), immunologic methods (e.g., ELISA)

Coronaviridae

• Appearance: Distinctive club-shaped projections under electron microscope
• Causes: 15% of cold-like infections in adults
• Transmission: Direct contact, droplets, or airborne routes
• Example: Coronavirus (SARS-CoV)

Filoviridae

• Marburg Virus: Now Lake Victoria marburg virus
• Symptoms: High fever (12-22 days), maculopapular rash, worsening nausea, vomiting, and diarrhea, bleeding from nose, gums, and GI tract, diffuse hemorrhaging, shock, multiple organ system involvement.

Flaviviridae

• Japanese Encephalitis Virus: Ranges from influenza-like illness to encephalitis
• Dengue Virus: Causes two distinct diseases (Classic Dengue Fever (DF) and Dengue Hemorrhagic Fever (DHF)) via mosquito bite.
• Yellow Fever Virus: Mosquito bite-borne disease.
• Symptoms: Fever, myalgia, headache, anorexia, nausea, and vomiting (asymptomatic, acute infection).

Natural Hosts, and Transmission Methods

• Saint Louis Encephalitis: Birds, Culex mosquitoes
• West Nile Virus: Birds, mosquitoes
• Zika virus: Mosquito
• Marburg Virus: Monkeys (infected monkeys or infected patients).

Influenza Viruses

• Transmission: Birds and mammals
• Symptoms: Flu, abrupt onset of headache, fever, chills, and dry cough (Later: high fever, myalgias, malaise, anorexia).
• Antigenic Variation: RNA replication errors cause antigenic drifts. Antigenic shifts occur when surface antigens change drastically, leading to new influenza subtypes (H or N).
• Important Types: H1N1, H3N2, H5N1

Parainfluenza Viruses

• Types: PIV-1 to PIV-4
• Cause: Respiratory disease in young children (croup, bronchiolitis)
• Transmission: Aerosolized droplets.

Mumps Virus

• Symptoms: Rhinitis, pharyngitis, bronchiolitis, pneumonia.
• Transmission: Droplets of infected saliva.
• Infection of parotid glands, and other areas like testes and ovaries

Measles Virus

• Symptoms: Abrupt onset of sneezing, runny nose, red eyes, fever, maculopapular rash (head and trunk), whitish spots (Koplik's spots)
• Complications: Otitis, pneumonia, encephalitis
• Transmission: Aerosol droplets
• Specimen of Choice: Nasopharynx and urine.

Respiratory Syncytial Virus (RSV)

• Cause: Croup, bronchitis, bronchiolitis, interstitial pneumonia.
• Transmission: Aerosolized droplets; specimen collection from: Aspirates, secretions, washes of the upper respiratory tract (URT)
• Detection: Hemadsorption, If, EIA.

Human Metapneumovirus (hMPV)

• Symptoms: Similar to RSV, Influenza, and PIV. Can vary from mild URT to acute lower respiratory infection.

Picornaviridae

• Enteroviruses: Hepatitis EVirus (HEV), Rhinovirus A, B, C, Coxsackieviruses, Polioviruses
• General: Infections of fever of unknown origin, aseptic meningitis, paralysis, sepsis, and other related conditions
• Symptoms: Ranges from flu-like illness to encephalitis

Retroviridae

• HIV: Bloodborne pathogen; transmitted by sexual contact or congenital infection, not transmitted by sweat, tears, saliva, or urine.
• Human T-cell Lymphotropic Viruses (HTLVs): Cause of some leukemias, sarcomas, and lymphomas
• Spherical Virus: Three layer structure (Two identical copies of ssRNA; nucleocapsid; a matrix shell; host cell envelope; glycoprotein trimmers).