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Microbiology (viruses) > orthomyxoviruses > Flashcards

orthomyxoviruses Flashcards

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1
Q

what are orthomyxoviruses?

A

are a family of RNA viruses that includes seven genera: Influenza virus A, Influenza virus B, Influenza virus C, Influenza virus D, Isavirus, Thogotovirus and Quaranjavirus.
influenza ABC are major determinant of morbidity and mortality caused by respiratory disease

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2
Q

myxo

A

mucus

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3
Q

three types of influenza virus

A

influenza A, B, C

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4
Q

structural composition of influenza

A

spherical shape
ss -ve sense RNA genome
types A,B - 8 segmented genome
type C- 7 segmented genome

9 different structural proteins

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5
Q

what are the 9 proteins of influenza?

A
  1. ribonucleoprotein (RNP)
  2. PB1,2, PA- bind to the RNP, responsible for
    transcription and replication
  3. Matrix (m1) protein- form a shell below the viral envelope
  4. lipid envelop- derived from cell
  5. glycoprotein- (hemagglutinin (HA))
    (neuraminidase (NA))
  6. M2 ion channel protein
  7. non structural protein (NP)
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6
Q

function of HA?

A

attach virus to cell surface receptor

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7
Q

function of NA?

A

used to release the virus from infected cell surface

it help to prevent self aggregation of viruses during viral release

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8
Q

what determines the antigenic variations of the virus

A

HA AND NA

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9
Q

minor antigenic changes

A

antigenic draft

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10
Q

major antigenic changes

A

antigenic shift

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11
Q

based on antigenic diff the virus is divided into ?

A

influenza A,B,C

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12
Q

influenza A

A

antigenic ally variably high

responsible for most cases of epidemic influenza in human

also causes disease in aquatic birds, horses and pigs

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13
Q

influenza B

A

may exhibit antigenic change

some times causes epidemic in human only

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14
Q

INFLUENZA C

A

antigenic ally stable

causes inf in swine and human

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15
Q

physiochemical character of influenza

A

withstands room temp
withstands dust
resistant at alkaline PH

destroyed by lipid solvent - phenol, ethanol, ether, formaldehyde

destroyed by uv rays and gamma rays

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16
Q

viral attachment, penetration and uncoating of influenza?

A

attaches to cell surface sialic acid by HA
penetrate within endosome by endocytosis
uncoat by fusion of the viral envelop with the endosome cell membrane

17
Q

viral replication of influenza

A

transcription and replication occurs in the nucleus
shuts down the host cell protien synthesis 3hrs after inf
new virus is produced within 8-10 hrs
-ve ss RNA forms +ve strand
then RNA replication starts
nucleiocapsids are assembled in the nucleus
virus moves out to the cell surface
the HA,NA are synthesized in the endoplasmic reticulum
HA, NA are inserted in the plasma membrane
the insertion is with the help of M1
viruses are released by budding
NA removes the salic acid from cellular surface gp

18
Q

pathogenesis of influenza

A

spread from person to person
inhaled virus is deposited on mucous of the respiratory tract or in the alveoli

incubation period- 18-72 hrs

the virus changes the ciliated columnar epithelial cell of the RT into round, swollen, nucleus shinks- pyknotic and fragment, vacolulization of the cytoplasm

cytoplasm shows inclusion bodies and the cilia are lost

release of virus allow it to spread to other cells in respiratory area
cell damage initiates acute IR with edema and phagocytic cells
1. release of interferons- protect viral spread
2. t cells- cytotoxicity damages the epithelium and lead to
3. secondary inf- strap, strept, h.influenza
4. URT and LRT inf- causes dry cough

  1. main physical findings is pyrexia ( peak of 38-41oc within 12hrs)
  2. Fever usually last after 3 days
  3. during the 2nd and 3rd day of the illness the systemic effect disappear
  4. at the 4th day, respiratory symptoms are high with laryngitis, pharyngitis, tracheobronchitits
  5. in adult system illness without respiratory symptoms is common
    viral spread start during onset of symptoms and peak within 24hrs then reduce over the next 5 days
  6. viremia is rare
19
Q

clinical features of influenza A

A

incubation period is short- 2days (vary fro 1-4)
the illness is chills, fever, headache, myalgia, anorexia, rhinitis, cough,ocular symptoms
1/3 of the patient will suffer from common cold

20
Q

clinical features of influenza B

A

symptoms resembles that of influenza A but milder

show more involvement of the go tract- gastric flu

21
Q

clinical features of influenza C

A

afebrile URT inf, usually occur in young children

22
Q

complication of influenza

A

1.primary influenza pneumonia-young adult/old people
can be fatal after a very short day
2. a bacterial pneumonia(s.aureus/ s. pneumonia) with biphasic fever
3. chest pain in old people
4. severe inf/sudden death occur in patient with
cerebrovascular disease
cardiovascular disease
chronic respiratory disease
5. disease in pregnancy- schizophrenia

23
Q

lab diagnosis

A

virus isolation-monkey kidney
baboon kidney
human embryonic kidney cells
presence of virus may be detected after 18hrs by hemmaglutination with human o gp or gurineapig roc

rapid diagnosis-bnasal aspirate, nasal wash
PCR

24
Q

treatment of influenza

A

oral amantadine HCL
rimantadine

They block the ion channel in the envelope and cell membrane during viral fusion

25
Q

prevention

A

rimantadine- M2- type A only
amantidine-M2- type A only
ZANAMIVIR-NA- type A and B but not yet approved
OSELTAMIVIR-NA- type A and B

26
Q

WHO recommendation

A

embryonate eggs cultivated viral vaccine- whole virus, subunit viral particle, surface antigen

annual influenza vaccine- for increased risk pple
chronic heart/lungs disease
asthma
renal disorder
hospital workers
older persons with influenza virus
27
Q

Epidemiology of influenza

A 
occurs worldwide
type A causes pandemics
all three go try antigenic drift
only A goes thru antigenic shift
A is isolated from- ducks, chickens, turkeys, geese, pigs and horses
28
Q

where do new HA and NA comes from

A

there are 13 HA and 9 NA that all circulate in birds, pigs , again and humans

29
Q

why no B pandemics?

A

SO FAR NO SHIFT

NO ANIMAL RESERVIOR KNOWN

Microbiology (viruses) (12 decks)

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