Orthomyx and Paramyx

Question 1

Which viruses constitute the orthomyoxviruses?

Answer 1

Influenza virus.

Question 2

Structural characteristics of orthomyoxvirus?

Answer 2

Neg single strand RNA virus, with 8 segment genome. Helical nucleoprotein structure surrounded by outer membrane (envelope) studded with glycoprotein spikes.

Question 3

What are the antigens of orthmyoxoviridae?

Answer 3

Hemagglutin promotes viral entry.

Neuraminidase promotes progeny virion release.

Question 4

What causes flu pandemics?

Answer 4

Genetic shift.

Question 5

What is genetic shift?

Answer 5

Reassortment of viral
genome segments, such as when segments of
human flu A virus reassort with swine flu A
virus.

Question 6

What causes flu epidemics?

Answer 6

Genetic drift.

Question 7

What is genetic drift?

Answer 7

Minor (antigenic drift)
changes based on random mutation in
hemagglutinin or neuraminidase genes.

Question 8

What are the clinical presentations of orthomyoxviridase?

Answer 8

Influenza, risk of bacterial superinfection (Staph aureus, S. pnuemo, and H. influenzae).

Question 9

How do the intranasal and IM flu shots differ?

Answer 9

IM = killed virus. Intranasal contains live attenuated temperature sensitive mutant that replicates in the nose but not in the lung.

Question 10

What is the M protein of orthomyxoviridae?

Answer 10

membrane proteins anchoring the N/A glycoprotein spikes on the inside of the viral lipid bilayer.

Question 11

How does the HA antigen work?

Answer 11

Binds to sialic acid receptors on host cells in upper respiratory tract -> activates fusion. Also bind sialic acid receptors on erythrocytes causing heme-agglutination if mixed with RBCs.

Question 12

How does the NA antigen work?

Answer 12

1) Neuraminic acid is part of mucin, the substance covering mucosal epithelial cells, part of defense barrier. Neuraminidase cleaves neuraminic acid, allowing HA to “see” the sialic acid receptors.
2) Neuroaminidase also cleaves attachment between HA of progeny virions and sialic acid host receptors, so progeny can be released.

Question 13

What are the serotypes of influenza?

Answer 13

A (humans, mammals, birds), B and C (humans only)

Question 14

Which serotype experiences genetic shift?

Answer 14

A only, because only A can be traded between different species (humans, swine, birds, etc)

Question 15

How do the adamantanes work?

Answer 15

Amantadine and rimantadine are M2 ion channel inhibitors. Inhibit influenza M2protein blocks acidification of the interior of the virion that is required for viral uncoating.

Question 16

Whats the problem w/ the adamantanes?

Answer 16

Can cause anxiety/confusion. Associated with rapid emergence of drug-resistant infectious isolates of influenza A. Majority of recent strains are resistant.

Question 17

What kind of drugs are zanamivir and oseltamivir?

Answer 17

Neuraminidase inhibitors - mimics the sialic acid receptor for catalytic site of neuraminidase. Effective against all strains. Prevents release of progency, limits severity of disease.

Question 18

What is the timeline for giving neuraminidase inhibitors?

Answer 18

Within first 36-48 hrs, decreases duration of illness by 1-2 days, decrease severity, appear to prevent secondary bacterial infection.
Can also be giving as ppx after exposure to infected close contact.

Question 19

What are the primary paramyxoviridae?

Answer 19

Parainfluenza, RSV, measles, mumps, metapneumovirus.

Question 20

What are the three structural differences between paramyx and orthomyx?

Answer 20

1) neg ssRNA is in one strand, not 8 segments
2) HA and NA are part of the same glycoprotein spike, not 2 different spikes
3) F protein = fusion protein that causes the infected host cells to fuse together into multinucleated giant cells

Question 21

Three big picture ideas to remember about paramyxo?

Answer 21

1) Lungs 2) Kids 3) Viremia; spread of infection to distant sites

Question 22

What is the clinical presentation most strongly associated with parainfluenza?

Answer 22

Croup- can also cause pretty much any upper respiratory tract symptoms.

Question 23

What is croup?

Answer 23

Parainfluenza inxn of larygnotracheabronch that occurs in children. Swelling of these structures produces airway narrowing. Results in seal-like barking cough and inspiratory stridor.

Question 24

What is the characteristic X-ray finding with croup?

Answer 24

Steeple sign - narrowing of upper trachea and subglottis. .

Question 25

What cardiovascular physical finding may be present with croup?

Answer 25

pulsus paradoxus due to upper airway obstruction.

Question 26

What’s different about respiratory syncytial virus than the other paramyxies?

Answer 26

No H/N glycoproteins! Just F.

Question 27

What is the clinical presentation associated with RSV?

Answer 27

Bronchiolitis and pneumonia in babies.

Question 28

What is the treatment of RSV? Prevention?

Answer 28

Ribavirin/supportive. Prevent with palivizumab, a monoclonal antibody against RSV for premature infants.

Question 29

What is metapneumovirus associated with?

Answer 29

Respiratory infections in children slightly older than the RSV population. Bronchiolitis/croup/pneumo. TX= supportive.

Question 30

Mumps virus - where does it replicate?

Answer 30

In upper respiratory tract and in regional lymph nodes, spreads via blood to distant organs.

Question 31

What is the clinical presentation of mumps?

Answer 31

Parotitis, Orchitis, and aseptic Meningitis. Infertility is a rare complication.

Question 32

What is another name for measles?

Answer 32

Rubeola.

Question 33

Where does measles virus replicate?

Answer 33

Respiratory and conjunctival membranes

Question 34

How long does the incubation period of measles last?

Answer 34

2 weeks.

Question 35

What is the classic prodrome of measles?

Answer 35

Cough, Coryza, Conjunctivitis, high fever to 105, malaise.

Question 36

What are the dermatologic manifestations of measles?

Answer 36

1) Koplik’s spots. “cop licking red/white/blue lollipop”. Red based lesions w/ blue-white centers in the MOUTH - that appear 1-2 days before rash.
2) Maculopapular rash spreading from head –> feet. Rash is gone in 6 days.

Question 37

What the heck are warthin-finkeldey cells?

Answer 37

Giant cells, fused lymphocytes found in measles. Associated with lymphadentitis, found in a background of paracortical hyperplasia.

Question 38

What happens with measles during pregnancy?

Answer 38

Associated with spontaneous abortion/premature delivery. Measles in pregnant women results in fetal death in 20% of cases.

Question 39

What is subacute sclerosing panencephalitis?

Answer 39

A slow form of encephalitis caused by measles. Many yrs after measles the patient may have slowly progressive CNS disease, with mental deterioration and incoordination.