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Y2 infection > influenza - optional > Flashcards

influenza - optional Flashcards

1
Q

when does seasonal influenza occur

A

during winter mths
dec-feb in northern hemisphere
jun-aug in southern hemisphere

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2
Q

link between influenza and sun

A

more severe epidemics occur every 11yrs - same as increased sunspot activity
sun’s radiation may cause mutations leading to antigenic shifts in viral RNA

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3
Q

influenza virus

A 
RNA virus 
8 segment genome 
orthomyxoviridae family 
3 main groups (A, B, C)
IfA infects mammals and birds
IfB and IfC infects only humans
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4
Q

surface proteins on influenza

A

haemagglutinin (H) - facilitates viral attachment and entry to host cell
18 different H antigens (H1-3 in humans)
Neuraminidase (N) - enables new virion to be released from host cell
11 different N antigens

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5
Q

what is antigenic drift

A

mechanism of genetic variation within the virus
occurs continually over time, small on-going point mutations in the genes coding for antibody binding sites
may change the antigenic properties and eventually the immune system will not combat the virus as well
causes worse than normal epidemics and vaccine mismatch

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6
Q

antigenic shift and new viral strains

A

abrupt major change in the virus
new H/N combinations
enables a flu strain to jump from one animal species to another
2 or more different strains of a virus combine to form a new subtype (new H/N combinations)
reassortment of the virus’s genes segments
new antigenic populations, population is unprotected and at risk, pandemics

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7
Q

seasonal vs pandemic flu

A

seasonal: occurs every winter, affects 10-15% of population, unpleasant but not life-threatening
pandemic: occurs sporadically, affects ≥25% of the population, more serious and more complications

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8
Q

antigenic shift and influenza

A

avian host
direct avian human transmission
swine host for both avian and human virus
new reassorted virus subtype is passed on to humans

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9
Q

pandemic requirements

A

human pathogenicity
‘new’ virus - antigenic shift, susceptible population
efficient person-person transmission

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10
Q

H1N1 pandemic infection and % affects

A 
30% infection rate
of the 30% infected: 
0.1-0.35% fatality rate
2% hospital treatment 
15% complications 
82.7-82.9% mild symptoms
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11
Q

age and mortality

A

higher in infants and young children
slight peak around 25-34y/o
mortality increases again in >50y/o

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12
Q

impact of H1N1 pandemic

A 
784 000 estimated cases of  ILI in england 
457 deaths in UK 
less severe illness than anticipated
25% global attack rate 
50% in school children 
majority of deaths in Africa
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13
Q

how is avian flu spread

A

spreads through direct contact w/ infected birds (dead or alive)
occasional transmission via close human to human contact (staff, caregivers)
no known transmission by eating properly cooked food/eggs

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14
Q

which strains of avian flu affect humans

A

only H5N1 and H7N9 strains affect humans

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15
Q

fatality rates of avian flu

A

60% H5N1

36% H7N9

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16
Q

clinical features of influenza

A

incubation period 2-4 days (up to 1-7)
abrupt fever up to 41C (commonly 38-40C) which lasts 3 days (1-5 days range)
plus 2 or more of: cough (sore through, rhinorrhoea), myalgia, headache, malaise
predominance of systemic symptoms
less common symptoms: N+V, diarrhoea

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17
Q

influenza like illness (ILI)

A

defined by WHO for epidemiological reasons
fever (>38C) AND cough, onset within last 10 days

if requires hospitalisation = severe acute respiratory infection (SARI)

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18
Q

transmission of influenza

A

airborne - person to person by large droplets (>5 microns)
direct contact - person to person
indirect contact - person to fomite to person

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19
Q

viral shedding - influenza

A

first 4 days of illness (range 1-7 days)

longer in young children and immunocompromised

20
Q

viral survival - influenza

A

24-48hrs on non-porous surfaces

8-12hrs on porous surface e.g. tissue

21
Q

risk factors for complicated influenza

A 
neurological, hepatic, renal, pulmonary and chronic cardiac disease
DM 
severe immunosuppression 
>65y/o
pregnancy (incl up to 2wks post-partum)
<6mths old 
morbid obesity (BMI ≥40)
22
Q

common respiratory complications of influenza

A

acute bronchitis

2y bacterial pneumonia (~20%) - appears 4-5 days after start of flu

23
Q

microbiology of 2y bacterial pneumonia

A

1918: H. influenzae, S. pneumoniae, beta haemolytic strep
1957: S. aureus (>2/3)
1968: S. pneumoniae (48%), S. aureus (26%), H. influenzae (11%)
community MRSA uncommon in europe, concern in US

24
Q

less common respiratory complications of influenza

A

1y viral pneumonia - appears common in human cases of avian influenxa (H5N1)
rapid resp failure (within 48hrs)
mortality >40% within 7 days)

25
Q

cardiac complications of influenza

A

less common
myocarditis
pericarditis

26
Q

CNS complications of influenza

A

less common
transverse myelitis/ Guillain Barre
myositis and myoglobinuria

27
Q

encephalitis lethargica

A

fever, headache
external ophthalmoplegia
lethargy
sleep reversal

25% mortality
postencephalitic Parkinsonism
serology +ve flu IgA
paralleled 1918-19 pandemic

28
Q

diagnosis and investigations for influenza

A

viral nose and throat swabs/VTS (molecular detection/PCR)
CXR - pneunonitis/pneumonia/ARDS
blood culture
pulse oximetry - SpO2 <92% need ABG and oxygen
resp rate
U+Es, FBC, CRP, (CRP monitoring recovery of pneumonia, should 1/2 in 4 days)

29
Q

2y bacterial pneumonis invesigations

A

pts w/ flu like symptoms and a fever for >4 days should have an urgent CXR
severity assessment w/ CURB65

30
Q

CURB65

A 
Confusion 
urea >7mmol/L
RR >30 
BP diastolic <60 OR systolic <90
>65y/o
31
Q

CURB65 score risk of death in next 30 days

A 
0 - 0.6%
1 - 3.2%
2 - 13%
3 - 17%
4 - 41.5%
5 - 57%
32
Q

2 examples of neuraminidase inhibitors commonly used

A

oseltamivir

zanamivir

33
Q

antiviral therapy - when to use

A

use ASAP and within 48hrs of symptom onset

but in complicated illness - should always be given no matter how long after onset of illness

34
Q

oseltamivir (tamiflu) dose

A

oral
>13y/o
75mg every 12hrs for 5 days

35
Q

side effects of oseltamivir

A

common - N+V, abdo pain, diarrhoea
less common - headache, hallucinations, insomnia, rash
cautions - renal dosing needed

36
Q

zanamivir (relenza) dose and adverse effects

A

inhaled or IV
only available as dry powder inhaler
dose - >12y/o, 10mg inhaled daily for up to 10 days
adverse effects - rare, occasional bronchospasm

37
Q

other antiviral therapy

A

peramivir
favipiravir
baloxavir marboxil

amantadine and rimantadine not used due to resistance

38
Q

peramivir (Alpivab)

A

neuroaminidase inhibitor
licensed in USA and approved by european medicines agency
IV infusion
for uncomplicated influenza

39
Q

favipiravir (Avigan)

A

viral RNA polymerase inhibitor
licenced in Japan for ‘re-emerging influenza viruses’
oral medication

40
Q

baloxavir marboxil (Xofluza roche)

A

endonuclease inhibitor

one single dose

41
Q

antiviral therapy in pregnancy

A

antivirals have been recommended due to the adverse outcomes in this group
oseltamivir is 1st line
no evidence of harm of either oseltamivir or zanamivir
no malformation, maternal toxicity or embryotoxicity observed in animal studies

42
Q

antiviral therapy in breastfeeding

A

only tiny amounts of oseltamivir in milk

current guidance is oral oseltamivir

43
Q

when does an individual become non-infectious

A

immunocompetent adults - 24hrs after last flu symptoms (fever and cough), or when anti-viral therapy is completed (which ever is longer)

immunosuppressed adults and young children - consider each case separately

44
Q

protection for healthcare staff

A

for most pts w/ suspected of proven flu: surgical face mask, plastic apron, gloved

wash hands after any examination

pts who are receiving nebuliser, NIV etc w/ aerosolised virus - face fit FFP3 respirator mask

45
Q

seasonal flu vaccine

A

prepared each year using viruses considered most likely to be circulating in the forthcoming winter
CI in those w/ egg allergy as grown in chick embryo
chemically inactivated and purified
trivalent vaccine - 2 type A and 1 type B subtype viruses
single 0.5ml IM injection
only adverse affect is sore arm

46
Q

new universal vaccine candidate

A

in phase 1 clinical trial
haemagglutinin (HA) head constantly undergoes antigenic drift
new vaccine candidate only contains HA stem - less likely to need updating each season
could provide wider and longer-lasting immunity

47
Q

why are healthcare workers vaccinated

A

protect themselves and their families
reduce risk to ‘at risk’ pts
reduced absence from work during influenza ‘surge’ activity

Y2 infection (15 decks)

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