Theme 1: Lecture 2 - Viral and prion pathogens Flashcards
What 4 structures might a virus consist of?
- genome (RNA or DNA)
- capsid (protein coat)
- Envelope (lipid bilayer)
- some viruses also carry their own enzymes
What are the 6 steps in the lifecycle of a virus?
- adsorption
- penetration
- uncoating
- synthesis
- assembly
- release
How are viruses classified?
- By the genetic material inside them
- DNA or RNA
- single or double stranded
- if single, +ve or -ve strand - presence or absence of an envelope
What is the structure of herpes virus, how many types are known to infect humans and what is their characteristic feature?
- double stranded enveloped DNA viruses
- 9 types known to infect humans
- characterised by their ability to establish latency and reactivate
What are 2 other names for herpes simplex 1?
- HSV-1
- ‘cold sores’
What is the mode of transmission of herpes simplex 1?
- direct contact with vesicle fluid from lesions
- latency in sensory nerve ganglion - periodic reactivations
What symptoms/syndromes does herpes simplex 1 cause?
- fluid filled vesicles/ ulcers to skin or mucous membrane - typically mouth (can also be found on genitals due to oral sex)
- encephalitis - brain inflammation
What is the commonest cause of viral encephalitis?
HSV-1
What are 2 other names for herpes simplex 2?
- hsv-2
- genital herpes
What is the mode of transmission of herpes simplex 2?
- direct contact with vesicle fluid from lesions
- latency in sensory nerve ganglion - periodic reactivations
- vertical (from mother’s genital tract after vaginal birth)
What symptoms/syndromes does herpes simplex 2 cause?
- vesicles/ ulcers to skin or mucous membrane (typically genitals/buttocks)
- meningitis
- neonatal herpes - severe disseminated viraemia (life-threatening)
What are the other disease names of varicella zoster virus?
primary infection = chicken pox
reactivation = ‘herpes zooster’, ‘shingles’
What is the mode of transmission of chicken pox?
- respiratory droplet from person infected
- direct contact with vesicle fluid
Where is latency established in varicella zoster virus?
dorsal root ganglia
What is the clinical presentation of chicken pox?
febrile (fever) illness with widespread vesicular rash
What are other disease names for Epstein Barr virus?
- glandular fever
- infectious mononucleosis
- ‘kissing disease’
What is the mode of transmission of Epstein Barr virus?
virus is shed in saliva and genital secretions
What is the primary infection of Epstein Barr virus and what can it cause?
infectious mononucleosis
-can cause tonsillitis, fever, lymphadenopathy, hepatospleomegaly
Why might Epstein Barr virus reactivate?
if unwell or immunosuppressed
How is epstein Barr virus an oncogenic virus?
associated with malignant B cell lymphoproliferative disorders
What is the mode of transmission of cytomegalovirus?
- saliva or genital secretions
- donated blood, stem cells or solid organs
- latency in myeloid progenitors/monocytes/ dendritic cells
What is the primary infection of cytomegalovirus?
infectious mononucleosis
What is congenital CMV infection?
- in infants morn to mothers who have the infection during pregnancy
- can cause retinitis, deafness, microcephaly, hepatospenomegaly
Reactivation of latent CMV in immunosuppressed patients can cause which conditions?
retinitis, colitis, pneumonitis
What are the 5 herpes viruses?
- herpes simplex-1
- herpes simplex-2
- varicella zoster virus
- epstein barr virus
- cytomegalovirus
What are the 7 known causes of the ‘common cold’?
- rhinovirus
- coronavirus
- influenza virus
- respiratory syncytial virus
- parainfluenza virus
- adenovirus
- enterovirus
What is rhinovirus and what is its mode of transmission?
- common cold
- aerosolised respiratory secretions (coughs and sneezes)
- droplets from nose and eyes
What are the symptoms of rhinovirus?
sneezing, nasal obstruction & discharge, sore throat, cough, headache and fever
What is the 2nd commonest cause of the common cold?
coronaviruses
What is the mode of transmission in coronavirus?
- aerosolised respiratory secretions (coughs and sneezes)
- droplets from nose and eyes
What are the subtypes of coronaviruses discovered?
Coronaviruses are divided into alpha and beta
Some beta coronaviruses include:
-COVID-19
-SARS
-MERS - Middle East respiratory syndrome - occurs from camels
Which respiratory viruses are zoonotic?
- coronaviruses
- influenza
What are the 3 types of influenza?
A, B and C
-Influenza A mutates regularly so strains vary yearly
What are the two important surface proteins found in influenza?
H&N
What is the H1N1 strand of influenza also called?
swine flu
What is the mode of transmission of influenza?
aerosolised respiratory secretions (coughs and sneezes)
What are the symptoms of primary influenza illness?
fever, myalgia, headache, cough, sore throat, nasal discharge
What secondary infection might occur post-influenza?
- bacterial lung infection e.g S.pneumoniae, H.influenza, S. aureus
- virus damages lung tissue so bacteria use this opportunity to colonise
What does RSV stand for?
respiratory syncytial virus
What is the mode of transmission of RSV?
Aerosolised respiratory secretions
RSV can cause bronchiolitis. What is this?
- inflammation of smallest airways - bronchioles
- causes cough, wheeze, hypoxia and apnoeas
- affects children under 2 yrs
What is the mode of transmission of HIV?
- virus is present in blood, genital secretions and breast milk
- transmitted vertically, sexually, needle stick
What is the clinical course of HIV?
- HIV targets helper T cells (CD4)
- 2-6 weeks after transmission, patients may develop acute seroconversion illness (flu-like)
- asymptomatic chronic infection follows (5-15 years)
- AIDS
- with regular and effective antiviral therapy, HIV+ patients can have normal life expectancy
What is AIDS?
Rise in viral load and fall in CD4, patients become vulnerable to opportunistic infections
What is a hepatotrophic virus?
virus that specifically effects hepatocytes
What are the 5 primarily hepatotrophic viruses identified?
HepA
Hep E
Hep B
Hep C
How is hepatitis A and E spread?
faeco-orally
How is hepatitis B and C spread?
blood borne
What is hepatitis D?
Defective virus, can only survive with hepB
What are the clinical symptoms of hepA and hepE?
Nausea, myalgia, fevers, jaundice, right upper quadrant pain
In Western Europe and North America, what is hepE associated with?
pigs/undercooked pork
In what populations is HepA more common in?
- lower socioeconomic groups
- returning tourists
- men who have sex with men
who might fulminant hepE affect badly?
infected pregnant woman - high mortality (25%)
What % of adults with HepA are asymptomatic?
50%
90% of children are
What % of adults with HepE are asymptomatic?
95%
What are the modes of transmission of HepB?
- vertical
- sexual
What is the clinical course of HepB infection?
- after transmission, acute clinical hepatitis may occur
- hepB is then cleared, or becomes chronic
How is risk of chronicity of HepB related to age?
inversely related - 90% of perinatally acquired infection progresses to chronic, vs 5% in adults
What might chronic hepatitis lead to?
cirrhosis–> hepatocellular carcinoma
What is the mode of transmission of HepC?
- Sharing needles, needle stick injuries, transfusion of contaminated products
- vertical (mother to child) & sexual transmission
In the UK, what % of PWIDs have hepC?
50%
What is the clinical course of hepC?
- 25% will develop acute clinical hepatitis
- 15% will clear virus, 85% will become chronically infected
- chronic hepatitis —> cirrhosis —> hepatocellular carcinoma
What are the 3 viruses that are transmitted via the GI tract?
- norovirus
- rotavirus
- enteroviruses
How is Norwalk (norovirus) transmitted?
ingestion/ inhalation of aerosolised vomit particles
What is the main clinical feature of norovirus/norwalk ?
vomiting
Which virus transmitted via the GI tract is a major cause of infant mortality in the developing world?
rotavirus
How is rotavirus transmitted?
faeco-oral - contaminated food/water, and aerosolised faeces, vomit
What are the symptoms of rotavirus?
fever, vomiting, watery diarrhoea
What are some examples of enteroviruses?
poliovirus, echovirus, cocksackie A and B
What is the mode of transmission and pathogenesis of enteroviruses?
- enteric route: face-oral, contaminated food/water
- replicate in gut, but do NOT cause GI symptoms
- from gut –> lymph nodes –> blood (CNS)
What are the important clinical syndromes caused by enteroviruses?
- fever-rash in children
- meningitis (>50% viral meningitis cases are enteroviruses)
- severe disseminated disease in neonate
- poliomyelitis
How is mumps transmitted?
- virus shed in saliva and respiratory secretions
- very infectious
What is the characteristic sign of mumps?
acute parotitis (infection of parodic glands) - unilateral or bi lateral
What is orchitis and what virus can it occur in?
inflammation of the testicles: affects 20-30% of males with mumps
What is a more severe condition caused as a result of mumps?
meningitis - can lead to meningoencephalitis and sensoneurial deafness
How is measles transmitted?
respiratory droplet transmission - very infectious
What are the 3 potential clinical syndromes developed as a result of measles?
- primary measles
- acute post infectious measles encephalitis (brain inflammation)
- subacute sclerosis pan-encephalitis (progressive, degenerative, fatal disease of CNS)
What are the symptoms of primary measles?
-fever
-3 C’s:
Coryza - inflammation in mucous membrane of nose
Cough
Conjunctivitis
-Koplik’s spots on inside of cheek
-maculopapular rash
What is another name for rubella?
German measles
Which is the most rare, out of measles mumps and rubella?
rubella
How is rubella transmitted?
droplet transmission from respiratory route
What are the symptoms of primary rubella?
- mild illness, fever, maculopapular rash
- arthralgia/arthritis (30%)
- slightly more severe in adults
What is congenital rubella?
- risk of foetal malformation is highest in first 12 weeks of pregnancy
- classic triad: bilateral cataracts, sensorineural deafness, cardiac defects
What are the other names for parvovirus B19?
- slapped cheek syndrome
- fifth disease
Why does parvovirus B19 cause transient anaemia?
Infects and kills erythrocyte progenitor cells
What are 3 important clinical syndromes caused by parvovirus B19?
- Erythema infectiosum - fever, coryza, fiery red rash to cheeks, ‘lacy’ rash to body
- transient aplastic crisis
- infection in pregnancy
What is a prion?
small, infectious particle containing protein but no nucleic acid
What might be the effect of a gene mutation on a prion?
- gene mutation leads to changes in folding pattern of protein
- prion becomes resistant to protease enzyme due to abnormal folding
- prion accumulates abnormal in cell
- promotes other proteins to abnormal fold
What are the modes of transmission of prion proteins?
-inherited (genetic defects)
or
-transmitted via consumption or direct exposure
What are 4 properties of human prion diseases?
- manifest in CNS
- Produce spongiform change in brain tissue
- have long incubation times
- are progressive and fatal
What is nvCJD?
- new variant Creutzfeldt-Jakon disease
- very rare
- progressive ataxia, depression, dementia then death
- associated with consumption of contaminated beef
What is BSE?
Bovine spongiform encephalopathy
