Influenza Flashcards
What percentage of the population is infected by influenza yearly?
15-20% of the world’s population
Name influenza’s viral family and its characteristics.
Orthomyxovirus; spherical, enveloped, ssRNA, (-) sense, segmented genome that replicates in the nucleus
What are the two key influenza surface molecules and their function?
Hemagglutinin and neuraminidase; HA binds sialic acid receptors for entry and can clump RBCs; NA cleaves sialic acid for exit and degrades mucin; HA is neutralizing and NA is non-neutralizing
What are the influenza subgroups and who can they infect?
A, B, and C. Only A can infect both humans and animals
What is the difference between antigenic shift and drift?
Drift is small antigenic changes; shift is caused by a major mutation, usually from a zoonotic recombination and causes a pandemic
How is influenza transmitted?
Large respiratory droplet transmission over short distances
What is the incubation period for influenza?
1-4 days from exposure
What is the illness period of influenza and when are patients infectious?
Adults shed virus from 1 day before symptoms to 5-10 days after symptom onset. By 3 to 5 days their infectious ability is greatly decreased; children may be infectious for 10 days or more; immunocompromised people may shed virus for several weeks
Name symptoms of influenza infection.
Abrupt onset of fever, myalgias (sore muscles), headache, pharyngitis, rhinorrhea, cough, and fatigue
What is the difference between primary and secondary influenza pneumonia?
Primary pneumonia is caused by direct infection of lungs by influenza virus with the resulting immune system-mediated tissue damage; secondary is caused by a bacterial pathogen that enters right afterwards (usually after a period of improvement); S. pneumonia, S. aureus, H. influenza, nosocomial gram (-) rods
What is Reye’s syndrome?
Unknown cause, though aspirin is implicated; rare, life-threatening syndrome in children following viral infection with influenza or varicella virus; fever, rash, encephalopathy, liver failure
What are four diagnostic tests for the flu and which is the current gold standard?
Viral culture (10 days); immunofluorescence (1-4 hours); PCR (1-6 hours, gold standard); rapid antigen detection (<30 min)
What are the the two common groups of antivirals for flu treatment?
Adamantanes and NA inhibitors
Name the mechanism, adverse effects, and usage of adamantanes.
(Ex: amantadine, rimantadine) They block the M2 ion channel to prevent uncoating; have CNS effect, anticholinergic effects, and are teratogenic; used against Influenza A
Name the mechanism, adverse effects, and usage of NA inhibitors.
(Ex: oseltamivir, zanamivir) Inhibits NA cleavage of sialic acid; well-tolerated; used on Influenza A and B within 48 hours of onset, but effectiveness is debated
