Naked RNA Viruses with Icosahedral Symmetry, Filamentous Enveloped RNA Viruses

•Genome: Single-stranded, positive-sense RNA (+ssRNA)

•Structure: Non-enveloped, icosahedral capsid

•Transmission: Fecal-oral (mostly enteroviruses), respiratory droplets (rhinoviruses)

Picornaviridae

Picornaviridae Key Genera:

Enteroviruses and Rhinoviruses

Enteroviruses Include:

•Polioviruses (types 1, 2, 3)

•Coxsackie A and B viruses

•Echoviruses

•Enteroviruses (non-polio)

•Hepatitis A virus (HAV)

Disease spectrum: Asymptomatic, mild illness, aseptic meningitis, or paralytic poliomyelitis

Poliovirus

Hand-foot-and-mouth disease (notably by A16 and A6)

Coxsackievirus A

•Herpangina

•Myocarditis and pericarditis (viral heart disease)

•Bornholm disease (pleurodynia): sharp chest pain due to muscle inflammation

Coxsackievirus B

Name: "Enteric Cytopathic Human Orphan viruses"

Echoviruses

Include newer types like EV-D68 and EV-A71

Non-polio Enteroviruses

Associated with:

•Respiratory infections

•Neurologic disease (e.g., encephalitis, AFM – acute flaccid myelitis)

•Hemorrhagic conjunctivitis

Non-polio Enteroviruses

Disease: Infectious hepatitis

Hepatitis A Virus (HAV)

Transmission: Fecal-oral, often from contaminated food/water

Hepatitis A Virus (HAV)

Hepatitis A Virus (HAV) Diagnosis:

Anti-HAV IgM via ELISA

Cause: Most common viral cause of the common cold

Rhinoviruses

Prefer 33°C (nasal mucosa temperature), thus infect upper respiratory tract

Rhinoviruses

•Genome: Segmented double-stranded RNA (dsRNA), 10–12 segments

Reoviridae

Structure: Non-enveloped, icosahedral, double-layered capsid

Reoviridae

Reoviridae Key Member:

Rotavirus

Primary cause of severe infantile gastroenteritis worldwide

Rotavirus

is a family of enveloped, single-stranded, negative-sense RNA (-ssRNA) viruses.

Filoviridae

Filamentous Enveloped RNA Viruses

Filoviridae

Named from the Latin word filum meaning "thread", due to their long, filamentous morphology

Filoviridae

Causes severe viral hemorrhagic fevers with high case-fatality rates.

Filoviridae

Filoviridae Genera

Ebolavirus, Marburgvirus, Cuevavirus

Filoviridae Biosafety Level

BSL-4

Ebolavirus Species

•Zaire ebolavirus (most virulent, CFR up to 90%)

•Sudan ebolavirus

•Bundibugyo ebolavirus

•Tai Forest ebolavirus

•Reston ebolavirus (non-pathogenic to humans, found in the Philippines)

Species: Marburg marburgvirus

Marburgvirus

Most virulent strain, CFR up to 90%. Responsible for major outbreaks including the 2014–2016 West Africa epidemic and 2018–2020 DRC outbreak. Basis for current vaccine (Ervebo).

Zaire ebolavirus

Moderate virulence, CFR ~50%. Caused recent outbreak in Uganda (2022). No approved vaccine yet.

Sudan ebolavirus

Discovered in Uganda (2007); lower CFR (~25–35%) compared to Zaire and Sudan strains.

Bundibugyo ebolavirus

Rare; only one known human infection (1994), from contact with an infected chimpanzee.

Taï Forest ebolavirus (formerly Côte d'Ivoire ebolavirus)

Found in non-human primates and pigs in the Philippines and China. Non-pathogenic to humans, but may cause asymptomatic seroconversion. Of biosurveillance interest.

Reston ebolavirus

Ebola Virus Disease (EVD) Incubation period:

2–21 days

FDA-approved therapies for Zaire ebolavirus:

•Inmazeb (REGN-EB3): Monoclonal antibody cocktail

•Ebanga (mAb114): Single monoclonal antibody

Live recombinant vaccine for Zaire ebolavirus

rVSV-ZEBOV (Ervebo):

Marburg Virus Disease (MVD) Incubation:

2–21 days

Marburg Virus Disease (MVD) Mortality rate:

24% to 88%, depending on outbreak and care quality

Marburg Virus Disease (MVD) Zoonotic reservoir:

Fruit bats (Rousettus aegyptiacus)