Orthomyxovirus

Question 1

Characteristics (of RNA viruses in general)

Answer 1

ssRNA - strand; have to carry their own RNA polymerase in order to be converted to +sense RNA that can then use host machinery

All - sense RNA are single stranded with the exception of reovirus

All RNA viruses replicated in the cytoplasm except this one- ORTHOMYXOVIRUS!

Question 2

Characteristics of orthomyxovirus

Answer 2

Enveloped, -ssRNA, segmented (8 segments)

The segmented viruses are: BOAR- bunyavirus, orthomyxovirus, arenavirus, and reovirus

Replicate inside the nucleus

Question 3

Family

Answer 3

Influenza A, B, and C

Question 4

Methods of mutations

Answer 4

Antigenic shift

Antigenic drift

Question 5

Antigenic shift

Answer 5

Sudden- cause pandemics

Reassortment of viral genome segments (mixture of surface antigens- H and N)

Question 6

Antigenic drift

Answer 6

graDual- cause epidemics

Point mutations cause gradual change in genome- random mutations in neuraminidase and hemagglutinin

Question 7

Influenza A

Answer 7

Associated with epidemics and pandemics (drift and shift respectively)

Question 8

Influenza B

Answer 8

More associated with endemics (drift)

Question 9

Hemagglutinin

Answer 9

aka HA; causes RBCs to clump together (silica acid residues on RBCs are bound by HA)

H1-3 are the ones that infect humans; determines the tropism

Anti-HA antibodies protect from future infections

Question 10

M2 protein

Answer 10

Proton channel that ensures that adequate pH is present for viral uncoating

Amantadine (also increases dopamine release in CNS- used for Parkinsons)/Rimantadine inhibit M2 to prevent uncaring (only works against Influenza A- but increased resistance found)

Question 11

Neuraminidase

Answer 11

Aka NA- Cleaves sialic acid to allow for virion release

Oseltamivir and anamivir (e.g Tamiflu)- prevent the release of the vision release (needs to be given early)

Question 12

Transmission

Answer 12

Respiratory droplets

From Dec to Feb (question including month can be indicative of influenza)

Question 13

Vaccines

Answer 13

Live attenuated (intranasal)
Killed (trivalent- 2A and 1B and quadrivalent- 2A and 2B)- children can receive this vaccine

Question 14

Major complication

Answer 14

Pneumonia (generally Staph aureus, as well as Strep pneumo)

Question 15

Board question key info

Answer 15

Kid receiving aspirin after flu like symptoms/ viral infection- bad because of Reyes syndrome (causes liver failure- fatty liver and encephalitis, along with fever, rash and vomiting)

Aspirin also uncouples oxidative phosphorylation (so can see extensive damage in hepatocytes)

Question 16

Associated conditions

Answer 16

Associated with Guillian-Barre syndrome (ascending paralysis)
CSF: high protein with low WBC counts (albuminocytologic dissociation)

Question 17

Virulence factors

Answer 17

Hemagglutinin
Neuroaminidase
M2 protein (only present in Influenza A)