Influenza Flashcards by Courtney Nesbitt

Meaning of Orthomyxovirus

ortho: correct or normal
myxa: mucus
virions bind to mucoproteins

How well did you know this?

Not at all

Perfectly

Virion components for Influenza

compact helical nucleocapsid

envelope derived from plasma membrane

How well did you know this?

Not at all

Perfectly

Genome components for influenza

linear ss RNA, negative sense
6-8 dif segments
each gene segment codes for 1 or 2 proteins

How well did you know this?

Not at all

Perfectly

(3) Distinctive Characteristics of orthomyxovirus

replicates in the nucleus, unlike most RNA virus
undergoes reassortment by exchanging genome segments between strains
reassortment generates new viruses that cause pandemic due to changed surface antigens

How well did you know this?

Not at all

Perfectly

How many influenzas are there?

3; influenza A, influenza B, influenza C

How well did you know this?

Not at all

Perfectly

Influenza A?

may cause large pandemics
significant morbidity & mortality
humans, swine, avian, marine mammals

How well did you know this?

Not at all

Perfectly

Influenza B?

Humans only
not associated w/pandemics
mild disease

How well did you know this?

Not at all

Perfectly

Influenza C?

Humans & Swine
not associated w/pandemics
mild disease

How well did you know this?

Not at all

Perfectly

Influenza A major surface antigens?

Hemagglutinin (HA)

Neuraminidase (NA)

How well did you know this?

Not at all

Perfectly

Hemagglutinin (HA)?

major surface antigen
serves as site of attachment to host cell
initiates infection

How well did you know this?

Not at all

Perfectly

How many antigenically distinct HAs have been identified?

15; H1 to H15

How well did you know this?

Not at all

Perfectly

How many antigenically distinct HAs have been identified for human influenza A?

3; H1 to H3

How well did you know this?

Not at all

Perfectly

Neuraminidase (NA)?

major surface antigen
enzyme that cleaves sialic acid from glycoproteins
plays a major role in replication of virus

How well did you know this?

Not at all

Perfectly

How many antigenically distinct NAs have been identified for influenza A?

9; N1 to N9

How well did you know this?

Not at all

Perfectly

How many antigenically distinct NAs have been identified for human influenza A?

2; N1 to N2

How well did you know this?

Not at all

Perfectly

What is a unique feature of influenza A?

frequency with which they can change antigenically

How well did you know this?

Not at all

Perfectly

_____ explains why influenza A viruses cause major epidemic & pandemic diseases in humans

antigenic variation

How well did you know this?

Not at all

Perfectly

What does antigenic variation involve? result in?

involve HA and NA

result in antigenic drift & antigenic shift

How well did you know this?

Not at all

Perfectly

(4) Characteristics of Antigenic Drift

Relatively minor changes that occur approximately every year
Associated with antigenic variation (mutation) in HA
Antigenic variation in HA results in an epidemic
Epidemics occur on average every 2.4 years

How well did you know this?

Not at all

Perfectly

(4) Characteristics of Antigenic Shift

Major changes in HA and NA produce “new” virus strain
The overall population has no herd immunity to new strain
Antigenic variation in both HA and NA results in a pandemic
Pandemics are unpredictable, but occur every 10 to 12 years

How well did you know this?

Not at all

Perfectly

Genome of influenza A consists of ____

segmented genome

8 distinct pieces of ss RNA

How well did you know this?

Not at all

Perfectly

RNA segment ____ encode for HA; RNA segment ____ encodes for NA

4;6

How well did you know this?

Not at all

Perfectly

What happens when 2 unrelated viruses infect the same cell?

16 RNA segments are relased

How well did you know this?

Not at all

Perfectly

2 influenza A+ 1 influenza B=

Trivalent

How well did you know this?

Not at all

Perfectly

How is influenza spread?

By respiratory droplets

The human infectious dose is ______ infectious virus particles, and the virus remains infectious for _____ after aerosolization. Retains infectivity on hard nonporous surfaces for ______. ____ may be involved in transmission.

1-5; 24 hrs

(6) Describe the pathogenesis of influenza.

1. initial site of infection is the respiratory tract mucosa 2. Virus shedding begins ~1 day before onset of illness 3. Systematic illness and respiratory syndrome present abruptly 4. Duration of shedding is gen 3-7 days 5. Fever & systemic complaints usually after 7 days 6. Recovery is slow

What do the complications of influenza include?

pneumonia & acute central nervous system manifestations

Death is usually due to pulmonary complications

secondary bacterial infection excessive expression of cytokines excessive hemorrhage

How many die on avg each year from seasonal influenza?

36,000 persons

Mortality is generally highest in______

young and among older adults

Excess morbidity & mortality highest in persons with?

cardiovascular conditions asthma renal dysfuntion HIV/AIDS

How many antiviral drugs are currently available for prevention and treatment of influenza? When is the greatest benefit?

4 (amantadine, rimantadine, zanamivir, TAMAFLU) | started within the first 24 hours

What are the 2 mechanisms of action?

uncoating & preventing maturation

Which drugs mechanism of action is uncoating of virus?

Amantadine & Rimantadine

Which drugs mechanism of action is preventing maturation of virus?

Zanamivir & Oseltamivir (tamaflu)

Where are inhibitors of uncoating most useful?

Nursing homes

What is the target for amantadine & rimantadine?

M2 protein of virus

Mechanism for uncoating

antivirals blocks channel formed by M2 protein, prevents entry of H+ ions into the virion, and thereby prevents release of RNA/nucleoprotein complexes into cytoplasm

(3) What are the purposes of the M2 protein of the virus?

Forms transmembrane channels that allow H+ ions to enter interior of virion during acidification within endosome Weakens interaction between matrix protein M1 and nucleocapsids Facilitates release of nucleocapsids into cytoplasm

Mechanism for preventing maturation

antivirals are designed to compete more favorably with sialic acid for binding to NA, prevent sialic acid cleavage, and thereby prevent release of virus

What is the target for zanamivir & tamaflu?

neuraminidase

Inactivated killed vaccines (trivalent) used for influenza?

virus grown in chicken eggs, purified, and formalin-inactivated protection about 70%-90% when good antigenic match

Live-attenuated vaccines used for influenza?

replicate efficiently at low temps induce mucosal immune response (IgA) use of nasal rather than parental route of admin more acceptable to pts

When and where was the first description of an influenza?

Europe 1510

In 16th century known as (2)

“the new acquaintance” | "the gentle correction”

In 17th century known as (3)

“the new delight” “the jolly rant” “la grippe"

In 18th century known as (1)

"the influence"--- INFLUENZA

The Great Influenza Pandemic of 1918-1919

20-100 million ppl died worldwide in one year Spanish press was first to report on the disease (known as the Spanish Flu) pandemic involved 3 waves of virus infection

First Wave of GIP of 1918-1919 (jan)

not more dangerous than previous influenza pandemics | deaths primarily among infants & elderly

Second Wave of GIP of 1918-1919 (aug)

Extremely virulent virus appeared in three locations High mortality rate in infants High mortality rate in persons 20 - 40 years of age

Third Wave of GIP of 1918-1919 (dec)

Less virulent than the second wave virus | Same high incidence of death in persons 20 - 40 years of age

When did the GIP end?

March 1919

What did the lung tissues of victims of 1918-1919 pandemic show?

Virus RNA contained sequences of swine influenza virus

1976 Swine Influenza Scare?

swine influenza virus isolated from fatal case of influenza in NJ & farmer and pig in Wisconsin National Immunization Program against swine influenza, so rapid development of vaccine administered in 45 million persons Swine influenza virus never entered the general population

What disease developed 4 to 6 weeks after vaccination during the 1976 swine influenza scare?

Guillain-Barre

2009 Swine Influenza Pandemic?

Outbreak of H1N1 influenza virus with genetic elements of swine influenza virus (possibly avian influenza virus) during summer months

Severe/Fatal disease of H1N1 highest in persons aged? Mortality?

20-40 years | far below 1918-1919 pandemic

The H1N1 influenza virus was resistant to which antiviral drug?

Tamaflu (Oseltamivir)

Influenza is caused by?

A tiny living poisonous plant