Microbiology-Influenza Flashcards
What is the incubation period of influenza virus?
1-4 days
How is influenza transmitted and where does it replicate?
Air droplets. Replicates in the respiratory epithelium
Why are people with the flu more susceptible to secondary bacterial infection?
The virus destroys the respiratory epithelium. It also elicits neutrophil and macrophage responses that damage the respiratory epithelium. This renders the airway more susceptible to bacterial infection.
A 16 year old female comes to your office with her mother complaining of headache, chills, cough, runny nose and myalgia. Her temperature is 102. Her mom is with her and said she had similar symptoms two weeks ago but is better now. Could the mom still be contagious?
Yes. Just being around her daughter puts her at risk for another infection. She feels better because her body has made serum specific IgA antibody against the virus. However, despite feeling better, the virus still sheds itself and can infect other people.
What is a rare, but sometimes deadly complication of influenza infection?
Respiratory epithelial damage so extensive that airways are inflamed, damaged and so full of mucous that you get pneumonia, ARDS and die.
A 31 year old male comes in complaining of fever, malaise, non-productive cough and a fever of 101. He said he came in because this morning he was unable to move his feet and can now not move his legs. What is your diagnosis?
Guillain-Barre syndrome associated with influenza infection.
Why is aspirin contraindicated in children with the flu?
It is associated with Reye’s syndrome
What serious neurological symptoms may present in someone with a serious influenza infection?
Encephalopathy or encephalitis.
Why is the influenza virus so prone to antigenic shift?
Its genome consists of 8 -ssRNA segments that can be freely mixed and matches with other viruses.
What allows influenza virus to bind to the cell it wants to infect? What about this peptide will make viruses more virulent?
Haemagglutinin (HA) binds to sialic acid on the membrane of the host cell and fuses to it when it is in the low pH lysosome. The more basic residues there are in the peptide, the more easily the virus can dissociate from the cell once infection has taken place.
What allows influenza virions to release from the infected cell?
Neuraminidase
What strain of influenza is most pathogenic to human?
Type A. It is found in many animal reservoirs and can jump to humans. It undergoes antigenic drift and antigenic shift.
What strain of influenza is largely confined to the human population?
Type B. It is less pathogenic because of this and additionally only can undergo antigenic drift.
What channel in the virus could you potentially block to keep it from infecting you?
M2. If H+ cannot enter through this channel the virus cannot disassemble and infect the cell.
Why is the influenza virus so susceptible to antigenic drift?
RNA-dependent RNA polymerase does not have proofreading activity. Thus, when influenza is being converted to an mRNA strand, many mutations go unchecked.
What viral protein is responsible for hydrolyzing the membrane so it can release its genetic material into the cell?
MMP. Matrix metalloprotease.
Where do viral genomic segments migrate to once they get into the cell?
The nucleus for transcription and replication
Which flu virus has a very high affinity for the cells in the lower respiratory tract and thus a very high mortality rate?
H5N1 avian flu. It has an affinity for the sialic acid in the lower respiratory tract and has a mortality rate of 50%.
What patient population should get the live attenuated vaccine and what population should get the trivalent inactivated vaccine?
Live attenuated = health 5-49 years old. Trivalent inactivated vaccine = 6 months + at high risk.
What are the targets of antiviral drugs used to treat influenza?
Neuraminidase inhibitors (oseltamivir & zanamivir) and M2 channel blockers (amantadine & rimantadine)
What antiviral therapies only work for type A influenza?
M2 channel blockers (amantadine and rimantadine)
What molecule do oseltamivir and zanamivir mimic?
Sialic acid. This is how they bind to and inhibit neuraminidase.
What are the targets of neutralizing antibodies for influenza?
HA and NA
