Orthomyxoviruses Flashcards
What shape are orthomyxoviruses?
Pleomorphic
Symptoms of Orthomyxo?
Febrile illness of upper and lower respiratory tract
Sudden onset of fever, cough, soreness, malaise, etc.
Most common serious complication of orthomyxo?
Pneumonia
Types of Influenza?
A, B, and C
Describe Influenza Type A
Most virulent human pathogen
Infect many animal species
Wild aquatic birds are a natural reservoir
Describe Influenza Type B
Milder than Type A
Only Humans
Mostly milder, mutate slowly
Describe Influenza Type C
No epidemics
Rarely causes disease
Nobody really cares…
What is an influenza proton pump called?
M2
What is M2 used for?
Uncoating
Describe the influenza genome?
-ssRNA, 8 segments
Influenza caspid? Envelope?
Helical
Yes
Where does influenza replicate?
The nucleus
Why does influenza rep. in the nucleus?
To hijack protons used to add the protective RNA cap
How does influenza enter a cell?
Binding of hemaaglutinin to cell surface
What targets neurominidase?
Tamiflu
Components of ribosomal RNA?
PA, PB1, PB2
Typical clinical manifestation of influenza?
Fever, Sore throat, myalgia, headache
Ocular symptoms (photophobia, tears, ache)
Weakness, fatigue, cough, GI probs
Two influenza complications…
Primary influenza pneumonia and secondary bacterial pneumonia
Describe primary influenza pneumonia.
Progressive cough, dypnea, and cyanosis
Infiltrative patterns without consolidation on radiograph
Who is at risk for primary influenza pneumonia?
3rd trimester women
elderly patients
Causes of secondary bacterial pneumonia?
Staph Aureus
Strep pneumoniae
Haemophilus influenza
What is the most serious complication of secondary bacterial pneumonia?
Staphylococcal pneumonia
Symptoms of staphylococcal pneumonia?
Severely ill
Hypoxemia, Elevated WBC, productive bloody cough, cavitary infiltrates on radiograph
Potential non-pulmonary complications of influenza?
Myositis
Cardiac Complications
Reye’s syndrome
Encephalitis
What is myositis?
Muscle inflammation
Examples of cardiac complications.
Myocarditis, pericarditis
What is Reye’s syndrome?
Swelling in Liver and Brain
Confusion, Seizures, Loss of Consciousness
Approx. 40% fatal in children/teens
What is contraindicated for childhood of adolescent fevers because of Reyes?
Asprin
What is encephalitis?
Fever, Headache, Seizures, Confusion, Loss of Consciousness, Coma
Groups at risk for encephalitis?
Esp. children younger than 7, adults older than 55
Pathogenesis of Influenza?
Virus establishes a local URT infection and kills epithelial cells
NA cleaves sialic acid residues in the mucus, providing tissue access
If into LRT, severe desquamination or epithelium
Immune/Inflammatory response triggered
How is influenza transmitted?
Mostly droplets, human-to-human
Also contaminated surfaces, pass to mouth
T or F. Influenza is stable at low temperatures and humidity.
True
What is seasonal influenza?
Inf. caused by antigenic drift
Closely related to the old ones
Could require opsinization or boost if large drift or immunocompromised
What is pandemic influenza?
Result of antigenic shift
Serious threat to global health, no pre-existing immunity
How many HA subtypes?
16
How many NA subtypes?
9
What carrier can hold all influenza viruses?
Birds
What HA and NA subtypes can humans carry?
H1-H3 and N1-N2
What is the difference between genetic drift and shift.
Drift – Minor change, same subtype
Shift – Major change, new subtype
How does antigenic shift happen?
Two viruses infecting a single cell, recombination on genome
What are the three ways antigenic shift can occur?
- Aquatic bird to host to human
- Intermediate host gets inf. from bird and human. New reassortment passes to humans
- Bird to human
How do influenza As all bind?
HN binding to proteins with sialic acid species
What sialic acids do human inf. prefer?
What sialic acids do bird inf. prefer?
alpha 2-6
alpha 2-3
Why can the bird and people share?
They both have some of both sialic acid residues
How to treat influenza?
Vaccine and Antivirals
What antivirals work against influenza?
Zanamivir and Oseltamivir
Rimantidine and Amantadine (only A)
What are the available vaccines for influenza?
Trivalent Inactivated Vaccine
Live attenuated vaccine
Cold or Flu? Fever, Headache, Fatigue, Cough
Flu
