Orthomyxoviruses Flashcards
The term that can describe orthomyxoviruses in terms of size and shape
Pleomorphic
Symptoms of orthomyxoviruses
- Illness of the upper and lower respiratory tract
- sudden onset of fever, cough, myalgia, malaise
- pneumonia most common serious complication
Three types of Influenza, an orthomyxovirus
Type A, Type B, Type C
Type A influenza virulency, natural reservoir, and affected animals
- most virulent human pathogens
- wild aquatic birds natural reservoir
- affects many animals
Type B influenza virulency, mutation ability, and affected animals
- mild virulency
- mutate slowly
- only humans
Type C influenza virulency and affected animals
- no epidemics
- infects human and swine
The types of influenza responsible for human pandemics
-Type A and Type B
Genome of influenza virus
- segmented 7-8
- negative DS RNA
- Type A and B(8)
- Type C(7)
- encoding 11 proteins
Capside and envelope of influenza virus
Helical and enveloped.
Location of influenza replication and assembly
Influenza replicated in the nucleus and assembled in the nucleus
Receptors on cell surface that the influenza virus bind to
Sialic acid
Process of influenza entering the cell
- binding to sialic acid on cell surface
- virus internalized in coated vesicle and transferred to endosome.
- acidification of endosome, uncoating of virus, release of capsid, release of viral RNA.
- Virus transported to nucleus
- synthesis of mRNA, RNA, proteins, and assembling all in nucleus
Incubation of influenza
-incubation period about 2 days, but may be 1-4.
Symptoms of influenza
- fever(100-104F)
- Sore throat 3-5days
- myalgia
- headache
- ocular symptoms - photophobia
- weakness and fatigue
- dry cough
- gastro-intestinal symptoms
Two major complications of influenza
- Primary influenza pneumonia
2. Secondary bacterial pneumonia
Characteristics of primary influenza pneumonia
- progressive cough, dyspnea, cyanosis
- bilateral diffuse infiltrative patterns on Xray
Individuals at risk for Primary influenza pneumonia
- women in third trimester of pregnancy
- elderly individuals
- cardiovascular disease
Bacteria responsible for secondary bacterial pneumonia
- Staph. aureus, Strep. pneumoniae, Haemo. influenza
- Staphylococcal pneumonia, most severe complication following 2-3 days.
Symptoms of secondary bacterial pneumonia
- hypoxemia
- elevated WBC
- bloody cough
Non-pulmonary complications of influenza
- myositis; muscle inflammation
- myocarditis and pericarditis
- reye’s syndrome; swelling in liver, brain
- encephalitis; influenza B
Pathogenesis of Influenza
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Epidemiology of Influenza
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Describe seasonal influenza
- arises principal as a result of antigenic drift
- annual boost vaccination
Describe pandemic influenza
- antigenic shift in the surface proteins
- whole population is at risk
Influenza subtypes and which in humans
- 16 HA subtypes H1-H16
- 9 NA subtypes N1-N9
- H1-H3 and N1-N2, H1-H3 pandemic
