Orthomyxovirus
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Viruses - RNA Viruses
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Fact List
- Orthomyxoviruses
- Characteristics
- RNA viruses
- replicate in the nucleus of cells
- Unlike most RNA viruses which replicate in cytoplasm of cells
- Single-stranded
- replicate in the nucleus of cells
- - sense
- Linear chromosome
- 8 segments
- Capable of antigenic shift
- Reassortment of entire genome segments as opposed to single point mutations lead to dramatic shifts in phenotype, causing pandemics
- Capable of antigenic shift
- Enveloped
- Helical capsid
- RNA viruses
- Key Viruses
- Influenza virus (flu)
- Contains antigens
- hemagglutinin (H)
- Binds sialic acid receptors on host cell to promotes viral entry
- neuraminidase (N)
- Promotes progeny virion release
- hemagglutinin (H)
- Contains antigens
- Influenza virus (flu)
- Presentation
- Fever, cough, sore throat, myalgias
- Patients at risk for fatal bacterial superinfection
- Esp. S. aureus, S. pneumo, and H. influenzae
- Treatment
- Supportive; pharmacological therapy depends on course and severity
- Oseltamivir (Tamiflu), zanamivir
- neuraminidase inhibitor, prevents progeny release
- Can also reduce viral penetration of mucous secretions on respiratory surface
- Can shorten course of infection if taken within 48 hours of onset of symptoms
- Amantadine
- Impairs uncoating of influenza A
- Limited use due to widespread viral resistance
- Used in other contexts (e.g. Parkinson’s disease) due to modulatory effects on dopamine
- Oseltamivir (Tamiflu), zanamivir
- Supportive; pharmacological therapy depends on course and severity
- Vaccination
- Achieved by antibodies against hemagglutinin (not neuraminidase)
- anti-H antibodies prevent infection, while anti-N antibodies can only decrease viral shedding and invasion
- contains viral strains most likely to appear during flu season, due to virus’ rapid genetic changes
- Killed viral vaccine (intramuscular)
- Also known as the “flu shot”; most frequently used
- Live attenuated vaccine (intranasal spray)
- contains temperature sensitive mutant that replicates in nose but not in lung
- Achieved by antibodies against hemagglutinin (not neuraminidase)
- Characteristics