Influenza

Question 1

What are the basic viral characterisitcs of the flu?

Answer 1

Enveloped, segmented, ss-negative RNA

Question 2

How many types of virus are there?

Answer 2

3 types: A, B. and C based on NP and M1, A further subdivided based on HA and NA

Question 3

What are the four surface proteins?

Answer 3

HA, NA. M2. and NS1

Question 4

What does HA do?

Answer 4

HA is responsible for virion attachment and reentry; antigenic domain + receptor binding sites; and increased AA substitution. It binds to sialic acid receptor, which is also found on RBCs-> agglutination

Question 5

What does NA do?

Answer 5

NA is responsible for virion release; inhibit NA to prevent spread (like TamiFlu). It cleaves neuraminic acid (mucin barrier), which exposes sialic acid for HA. On release, it cleaves HA-sialic acid

Question 6

What is M2 involved with?

Answer 6

M2 is only found with sibtype A. It’s an ion channel involved in uncoating virus; target of aman-/rimantadine. M2 allows H+ into the endosome; lower pH=dissociation of viral protein

Question 7

What is NS1?

Answer 7

IFN antagonist; it decreases host mRNA processing

Question 8

How many segments are found in each flu subtype?

Answer 8

A/B have 8 segments; C has 7 and no NA gene.

Question 9

How does a new influenza stain develop?

Answer 9

Reassortment of genes b/w co-infected human and animal influenza

Question 10

How is the flu transmitted?

Answer 10

Human airborne droplets (coughing, sneezing, talking, and it’s found on surfaces).

Question 11

What species serve as reserviors for the virus?

Answer 11

Humans, avian, and swine

Question 12

What is imporant about the avian reservior?

Answer 12

Allows reassortment and extra-human reservior

Question 13

Humans are a reservoir for what subtype(s)?

Answer 13

B/C

Question 14

What is antigenic drift?

Answer 14

Minor point mutation in HA and NA during viral replication from increased immunity

Question 15

What is antigenic shift?

Answer 15

Major changes in HA/NA during reassortment -> pandemic b/c new strain = zero immunity

Question 16

When is flu season (A/B)?

Answer 16

Winter and spring

Question 17

What causes most deaths with influenza disease?

Answer 17

Lower respiratory complications

Question 18

What is a complication of flu infxn?

Answer 18

Pneumonia

Question 19

Describe primary viral pneumonia vs secondary bacterial (superinfection)

Answer 19

Primary: abrupt onset; deterioration in 1-4 days.

Secondary: bacterial infxn during or after viral recovery

Question 20

What complication can occur from influenza during pregnancy?

Answer 20

Cause fetal loss and congenital malformation (2-3 trimester)

Question 21

There is increased shedding time in which patients?

Answer 21

The elderly and immunocompromised

Question 22

What complications are children at an increased risk for?

Answer 22

Because of their decreased immunity, children are at a higher risk for getting pneumonia, meningitis, and encephalitis. Use acetometaphin and NOT aspirin to Tx kids with fever

Question 23

What is the presentation of disease?

Answer 23

Upper and lower respiratory tract infxns.

1. Flu like symptoms: Fever, chills, HA, fatigue, myalgia, runny nose, sore throat, and dry cough
2. Short incubation (2days)- rapid onset
3. Systemic symptoms go away but respiratory persist
4. If pneumonia, then hemoptysis and SOB

Question 24

How do you make the Dx?

Answer 24

1. Swab nasopharynx for rapid antigen dectection (immunoassay)
   - titers peak at 48 hrs (before symptoms)
   - NO increased neutrophils or peripheral white cells=Viral
2. RT PCR

Also rule out bacterial cause; bacteria will have productive cough with increased neutrophils and positive pneumococcal culture

Question 25

What’s the Tx?

Answer 25

Vaccination is most important to decrease morbidity/mortality.

1. Amantadine/Rimantidine: inhibit M2 ion channel (effective only in A)
2. Zanamirvir/Oseltamivir: NA inhibitors; prevent viral release/spread (A/B)