Viral and Prion Pathogens Flashcards
what are viruses
simple micro-organism not capable of independent existence
require energy and enzymes from host
what are the 4 components that make up a virus
genome (RNA or DNA)
Capsid (protein coat)
envelope (lipid bilayer)
(some carry their own enzymes)
what is the 8 step life cycle of a virus
attachment entry uncoating 4-6 synthesis assembly release
what are the classifications of virus
genetic material - DNAvsRNA, single vs stranded
single, positive, negative
presence or absence of an envelope
what is the structure of the herpes virus and how many types are there
double stranded enveloped DNA virus
herpes simplex 1 herpes simplex 2 varicella zoster epstein barr cytomegalovirus 6a 6b 7 8
what is the herpes virus characterised by
its ability to establish latency and reactivation
what is the difference between simplex 1 and simplex 2 of herpes
HSV-1 cold sores - leading cause of encephalitis, high mortality rates
HSV-2 - genital herpes which can be followed by meningitis
what is the exposure difference between HSV 1 and 2
1 about 80% have experienced
2 about 10-20 of population
what is the mode of transmission of herpes
direct skin, sexual contact, eye contact with fluid vesicle,
describe the latency in HSV-1 vs 2 in sensory neurones
1 - trigeminal nerve ganglion hence face outbreak
2 - sacral ganglia hence outbreak on pubis
what are the 4 clinical syndromes associated with herpes
ulcers to skin
encephalitis (HSV1)
meningitis (HSV2)
neonatal herpes - give to child which can cause sepsis of child
what is varicella zoster virus
type of herpes (3)
chicken pox is primary and reactivation is shingles or herpes zoster
what is the mode of transmission of varicella zoster virus
respiratory droplet from person with primary
vesicle fluid with primary or reactivation
what is the latency established by in varicella zoster
dorsal root ganglion across CNS as reactivates across the body
what are the clinical syndromes of varicella zoster
chicken pox - widespread rash - potential complications of pneumonia, encephalitis
shingles - reactivation causing unilateral vesicles in a dermatomal distribution
what is epstein barr known as
herpes virus (4) glandular fever or infectious mononucleosis
what is the mode of transmission of EBV
what is it associated with
virus is shed in saliva and genial secretions (kissing disease)
associated with b cell malignancy (abnormal proliferation)
what are the two clinal syndromes associated with EBV
primary infection glandular fever - sore throat, fever, lymphadenopathy, atypical WBC’s - mononucleosis
reactivation - latency in B cells, risk for immunocompromised - lymphoproliferative disorder
what CMV and what is the mode of transmission
CMV - cytomegalovirus - herpes virus (5)
salvia or genital secretions
donated blood, stem cells or organs
what is the latency associated with in CMV
monocytes, dendritic cells and myeloid progenitors
what are the clinical manifestations of CMV
infectious mononucleosis
congenital CMV - produce babies with retinitis, deafness, microcephaly, cause distinct rash
immunosuppressed transplant recipients
people with advanced HIV - reactivation of latent CMV causing colitis
what is rhino virus - mode of transmission and clinical aspects
respiratory virus
common cold
aerosolised respiratory secretions and droplets from nose and eyes
symptoms - sneezing, nasal obstruction, sore throat, cough, headache, fever
what is respiratory syncytial virus, epidemiology, transmission and clinical aspects
RSV
comments in young children, mainly occurs in winter
aerosolised in respiratory secretions
bronchiolitis - affects children under 2 - inflammation of small airways - cough, wheeze, hypoxia and fever
what is the epidemiology of HIV and mode of transmission
36.7 mil global - 70% sub-saharan
about 0.25% of uk
virus present in blood, genital secretions
breast milk
ie transmitted vertically, sexually and needlestick
what is the clinical course of HIV
targets helper T lymphocytes (CD4)
2-6 weeks after transmission patent develop acute seroconversion illness ie fever sore throat and lymphadenopathy
can have asymptomatic chronic infection
when does HIV become AIDS and how can this be fatal
increase in viral load and fall in CD4 where patient can be killed by opportunistic infections: TB, pneumonia, meningitis, cerebral toxoplasmosis
what are the 5 hepatitis viruses and what are the two classes they are split into
face-oral:
Hep A/E
Blood borne:
Hep B/C
Hep D but defective and can only survive with Hep B
what is the epidemiology of Hep A compared to E
A: mainly children under 5 in endemic countries
E: mainly young adults, asia and africa
geno 1 and 2 = water
geno 3 associated with pigs and meat (pork)
what is the mode of transmission of Hep A and Hep E
face-oral virus - virus shed in faeces of infected individual
what are the clinical symptoms of hep A and E
nausea, myalgia, arthralgia, fevers
jaundice and right upper quadrant pain
what are the symptomatic populations of hep A vs E
A: infection in children is sally asymptomatic but 50% adults show symptoms
E: majority asymptomatic and only show in 2-5%
what are special considerations of Hep A and E
A: associated with lower socio-economic groups, returning tourists and MSM
E: high mortality in pregnant women (25%)
more severe in older males with liver disease
what is the epidemiology and mode of transmission of Hep B
more than 500,000 deaths annually
vertical, sexual and parenteral transmission
what is the clinical course of Hep B
acute clinical hepatitis
90% children and 50% young adults are asymp
Hep B is cleared or chronic
the older you are when you acquire it the less likely it will turn chronic
chronic hep = cirrhosis = heptocellular carcinoma
acute hep doesn’t cause long term damage
what is the epidemiology and mode of transmission of Hep C
170 mil infected, causes highest % of carcinomas
low prevalence in developed countries
IVDU (drug users), needlestick injuries, transfusion
vertical and sexual transmission but less common
what are the important clinical aspects of Hep C
after transmission about 25% develop acute clinal hepatitis
15% clear but most become chronic which then causes cirrhosis and hepatocellulr carcinoma
what is norwalk virus
norovirus - ssRNA virus (positive sense singleton’s stranded)
what is the epidemiology of norwalk virus and mode of transmission with its main clinical aspect
common - 90% infected at some point, short lived immunity less than a year and associated with point-source outbreaks
ingestion/inhalation of aerosolised vomit particles
vomiting is dominant feature
what is rotavirus
dsRNA - looks like wheel on election microscope
what is the epidemiology of rota virus and mode of transmission with its main clinical aspect
childhood virus 1-3 y/o
major cause of infant mortality in developing world
face-oral aerosolised in water and food
fever, vomiting, watery diarrhoea
what are enteroviruses - give examples
more than 70 types
it replicate sin the GI tract but no GI symptoms
poliovirus, coxsackie A and B, enterovirus and echoviruses
what is the epidemiology and mode of transmission of enteroviruses
worldwide, peak in sumer, 75% in 15 y/o or under, 90% asymp or mild symp
what is the mode of transmission of enertoviruses and pathogenesis
energetic route, feaco-oral, contaminated food/water
replicate in GI but no GI symptoms
from gut to lymph nodes to blood - vireamia
what are the clinical symptoms of enteroviruses and give specific examples
fever-rash, hand, foot, mouth, cold symps,
meningitis (most cases of men are caused by entero)
encephalitis
herpangina - Cox A
Pericarditis - Cox B
what is the epidemiology and transmission of mumps
childhood infection peaking in winter
virus shed in saliva and respiratory secretions via droplet transmission
what are the three clinical aspects associated with mumps
acute parotitis - inflammation of parotid glands
orchitis - inflammation of testicles (20-30% of males)
meningitis occurs in about 15% which can lead to deafness
what is the epidemiology and mode of transmission of measles
occurs in unvaccinated children
droplet transmission, highly infectious (still present in environment after 2 hours)
what are the 3 clinical aspects of measles
primary - fever, cough, conjunctivitis, kopliks spots on inside of cheek
maculopapular rash
acute post infection encephalitis 1:1000 - high mortality, immune mediated - 7-10 days after infection
subacute sclerosing pan-encephalitis - 7-10 years after infection, progressive and fatal
what is the epidemiology of measles and mode of transmission
german measles - vaccinated but previously common
droplet transmission - respiratory
what are the 3 clinical aspects of measles
primary postnatal rubella: mild illness, rash, fever, arthritis occurs in 30% adults
congenital rubella: triad: bilateral cataracts, sensorineural deafness and microcephaly (similar to CMV)
foetal malformation is highest in first 12 weeks preg
what is parvovirus B19, epidemiology and mode of transmission
slapped cheek syndrome, fifth disease
later winter, early summer, 50% infected by 15, 90% by 90
droplet, respiratory
what is the specific pathology of parvovirus B19
infects and destroys erythrocyte progenitors cells causing transient anaemia
what are the clinical aspects of parvovirus B19
erythema infectosium - fever, fiery red rash on cheeks
transient aplastic crisis - affects those with high RBC turnover such as sickle cells
dyspnoea, confusion
infection in pregnancy - 7-10 % foetal loss, hydrops fettalis (severe fetal anaemia, ascites)
what is a prion
small infectious pathogen containing protein but not nucleic acid
where do we normally find prions
in natural cells, gene mutation leads to changes in folding pattern which becomes resistant to protease enzyme, accumulates and becomes pathogenic
what are the two types of abnormal prions
inherited (genetic) or transmitted by infected meat/ material
what properties are shared by human prion diseases
pathologic manifestations confined largely to CNS
produce spongiform change in brain tissue
long incubation times
progressive and fatal
what is new variant CJD
nvCJD - sopradic cruz felt jacobs disease - rare, 1 in mil
progressive ataxia, depression dementia and death
what is nvCJD linked to
BSE - bovine spongiform encephalopathy - same structure prion - consumption of infected beef
