Influenza

Question 1

What viral family does Influenza belong to?

Answer 1

Orthomyxoviridae

Question 2

What type of genome does Influenza have?

Answer 2

segmented negative RNA genome, 8 segments

Question 3

How are influenza isolates named?

Answer 3

Species infected; H and N type

Question 4

H and N are… ? In relation to the influenza virus

Answer 4

the spikes on the surface of the virus

Question 5

H produces _____?

Why?

Answer 5

hemagglutinin (16 types)

Cell attachment, important for host tropism; has cleavage site that controls tissue tropism and spread, affects disease severity

Question 6

N produces _____?

Why?

Answer 6

neuramidase (9t types)

aids in release of the virus from the cells

Question 7

Why is a segmented genome good for a virus like influenza?

Answer 7

allows for rapid genetic evolution (mix n’ match)

Question 8

Why can influenza rapidly evolve genetically?

Answer 8

segmented genome

Question 9

What is an antigenic change?

Answer 9

When a viral genome changes enough so as to to prevent immune protection (not quite the same virus as last time)

Question 10

What is antigenic drift?

why does this happen in influenza?

Answer 10

accumulation of single nucleotide changes, gradual over a long period of time

no prrofreading mechanism, mistakes are passed to progeny

Question 11

What is antigenic shift?

how does this happen in relation to influenza?

Answer 11

genetic reassortment/change in combination of segments

animal infected with 2 different strains can produce new strains from genomic mix n match

Question 12

Viral replication?

Answer 12

H involved with adsorption

N involved with Release

Question 13

It was formerly believed that pigs were the “melting pot” for new flus, however…

Answer 13

we as humans may be!

Question 14

Is an epidemic more likely to come from an antigenic drift or shift?

Answer 14

antigenic shift; antigenic drift is responsible for allowing people to be infected multiple times by the “same” virus

Question 15

Anti virals were first discovered in ____ against herpesvirus by ____

Answer 15

1960s; “hit or miss”

Question 16

____ in 1980s turned attention to antivirals

Answer 16

AIDS

Question 17

Antivirals are difficult to design because _____.

Typically ____ an enzyme required for _____.

Must be take _____ or _____.

Answer 17

• most also damage host cells
• inactivate
• viral replication
• prophylactically
• early in infection

Question 18

There are drugs that block various stages of the viral replication cycle, such as…

Answer 18

• entry (amantadine)
• viral component synthesis (AZT)
• release (neuraminidase inhibitors)

Question 19

H5N1 - High Path Avian Influenza

Answer 19

• Low pathology strain exits in US poultry and wildlife, no clinical signs in most poultry or wild birds
• High pathology strain arose in Asia in 1996, found in Africa, Europe and Asia, has killed thousands of turkeys, chickens, and geese
• First human case 1997, 562 human cases in 15 countries 59% fatality

Question 20

Swine Flu vs Novel H1N1

Answer 20

• Influenza isolated from swine 1930
• Shifted from seasonal disease to year round endemic
• H1N1 in US swine at least 75 years; not the most predominant now and not the “novel H1N1”
• Zoonotic disease
• Novel H1N1 does not appear more severe for swine, may be for some subgroups of humans

Question 21

National Animal Health Laboratories Network (NAHLN) diagnostic testing in Emergency responses

Answer 21

• Same PCR protocol for all laboratories
• Positives confirmed by appropriate government agency, only virus isolation positive samples considered “true” positives

Avian

• Avian flu surveillance in migratory wild birds, ended Spring 2011
• State organizations sampling poultry

Swine (H1N1)

• Focus on clinically ill animals and those associated with human cases
• A basis for further study of what influenzas are circulating in swine
• Addition of testing feral swine

Question 22

A POSITIVE result is defined as the presence of a product and is typically interpreted to indicate that the pathogen in question was present in the sample.

• Reasons for “false positives” include: _____
• “True positive” results can be difficult to interpret:_____

Answer 22

• Contamination (field, lab)
• Recent use of MLV vaccines
• Residual nucleic acid from past infections (e.g. a latent herpesvirus infection)
• Nonspecific amplification that produces a product of the same size, less of a problem in real-time
• The extreme sensitivity of PCR allows detection of very small quantities of genomic material.
• Numerous examples exist where the virus/bacteria may be present yet cause no disease (FIP/FeCV, PCV-2).

Question 23

A negative result is defined as the absence of a product.

Reasons for “false negatives” include:_____

Answer 23

• Divergence between the sequence of the pathogen and that of the nucleotide primers
• Presence of endogenous inhibitors in the sample
• Fecal samples require additional steps for nucleic acid extraction
• Hemoglobin is a known inhibitor of PCR
• Heparin is a known inhibitor of PCR
• Autolysis/sample degradation (probably more of a concern with RNA viruses)
• Improper sample selection (wrong tissue, wrong time)

Question 24

Other tests:

Answer 24

• Virus isolation-viable virus
• Serology- rapid testing, subtype testing, confirms exposure