Microbiology - Virology Flashcards
What is the virology of HSV?
- Enveloped dsDNA genoma
- Lies latent in sensory neurones
What is the clinical picture of Herpes labialis (cold sores - HSV1)?
- Incubation: 2-12/7
- Severe painful ulceration
- Tendency to coalesce
- Erythematous base
- Fever
- Submandibular lymphadenopathy
What is the clinical picture of HSV2 (genital ulceration)?
- Incubation: 4-7/7
- Fever
- Dysuria
- Malaise
- Inguinal lymphadenopathy
- Painful
- Vesicular rash
- Herpes meningitis 1-2/52 later in <8% of primary genital herpes
- SACRAL RADICULOMYELITIS (urinary retention) = self-limiting
How does HSV present in an immunocompromised patient?
- Cutaneous dissemination
- Oesophagitis
- Hepatitis
- Viraemia
How does HSV present in a congenital infection?
Neurological:
- Microcephaly
- Encephalomalacia
- Hydranencephaly
Skin:
- Scarring
- Active lesions
- Hypo- + hyperpigmentation
Eyes:
- Microphthalmia
- Retinal dysplasia
- Optic atrophy +/- chorioretinitis
What is the treatment of HSV?
- Aciclovir = guanosine analogue
OR - Valaciclovir
What is the MoA for aciclovir?
- Guanosine analogue
- Competitively inhibits viral DNA polymerase by acting as analogue to deoxyguanosine triphosphate (dGTP)
- Incorporation of aciclovir triphosphate into DNA results in chain termination
- Absence of 3’ hydroxyl group prevents attachment of additional nucleosides
What is the virology of VZV?
- Enveloped dsDNA genoma
- Lies latent in sensory neurones, hence dermatomal distribution when reactivated
How does chicken pox present?
- Fever
- Malaise
- Headache
- Crops of rash follow prodromal Sx (Dew on rose petal)
- Lesions scab after 1/52 (no longer contagious)
What are some complications of chicken pox?
General:
- Scarring
- Pneumonitis
- Haemoorrhage
- Eye involvement
- Reye’s syndrome
Neurological:
- Acute cerebellar ataxia
- Guillain Barre
- Ramsey Hunt syndrome (facial palsy + vesicles in ear)
- Geniculate ganglion of CNVII (hearing loss + vertigo)
- Encephalitis (vasculopathy)
- Post-herpetic neuralgia (pain in dermatome)
How does shingles present?
- Reactivation caused stress or decreased immunity (e.g. immunocompromised or >50yrs)
- Painful rash in specific dermatome
How does VZV present in an immunocompromised patient?
- Rare complications more likely
- Acute retinal necrosis
- Progressive outer retinal necrosis (PORN)
- Mutlidermatomal shingles
How does VZV present as a congenital infection?
Eyes:
- Chorioretinitis
- Cataracts
Neurological:
- Microcephaly
- Cortical atrophy
MSK/Skin:
- Limb hypoplasia
- Cutaneous scarring
How does VZV present in a neonate?
- Purpura fulimans
- Visceral infection
- Pneumonitis
Why are vesicles on the nose concerning for a patient with shingles?
Risk of ophthalmic herpes zoster which is a medical emergency
What are vesicles on the ears indicative of for a patient with shingles?
Risk of Ramsey Hunt Syndrome
What is the management for a patient with chicken pox?
Aciclovir 800mg PO 7/7 OR Valaciclovir 1g TDS IF:
- Adults with chickenpox (risk of complications)
- Neonates
- immunocompromised
- Eye involvement
- Pts presenting with pain
Post-exposure prophylaxis = VZIG IF:
- Pregnant woman
- Immunocompromised
Live vaccine against varicella = attenuated
- Oka strian (CI = pregnancy)
What is the treatment for shingles and when is it indicated?
Indications: (IF <24hrs of rash)
- Symptomatic children
- Healthy adult smokers
- Chronic lung disease
- >20/40 gravid
Tx:
- Aciclovir 800mg PO 5x daily
- Famaciclovir 250mg PO TDS
- Valaciclovir 1g PO TDS
- Topical eye drops + oral for ophthalmic
- PEP 7-9/9 for immunocompromised (IVIG)
How is VZV diagnosed?
Exam:
- vesicles
Cytology:
- Scrapings for multinucleated giant cells (Tzanck cells)
Immunofluorescence Cytology:
- Cells from vesicles
PCR:
- Especially if rash is old, CNS + ocular disease
What is the virology of HCMV (human cytomegalovirus)?
- Enveloped dsDNA genome
- Lies latent in monocytes + dendritic cells
- CMV cells = OWLS EYE INCLUSIONS
How does HCMV (human cytomegalovirus) present in an immunocompromised patient?
ERPC (M):
1. E: Encephalitis
2. R: Retinitis
3. P: Pneumonitis
4. C: Colitis
(5. Marrow Suppression)
How does HCMV (human cytomegalovirus) present as a congenital infection?
- Ears: Sensorineural deafness
- Eyes: Choreoretinitis
- Heart: Myocarditis
- Neurology: Microcephaly, Encephalitis
- Lung: Pneumonitis
- Liver: Hepatitis, Jaundice, Hepatosplenomegaly
What is the treatment for HCMV (human cytomegalovirus)?
- Ganciclovir IV / Valganciclovir PO
- Foscarnet IV
- Cidofovir IV
IVIG = adjunct in pneumonitis
What is the mechanism of action of ganciclovir?
guanosine analogue chain terminator
What is the mechanism of action of foscarnet?
- Non-competitive inhibitor of viral DNA polymerase
- Pyrophosphate analogue, inhibits nucleic acid synthesis without requiring activation
- NEPHROTOXIC
What is the mechanism of action of cidofovir?
- Cytidine analogue chain terminator
What is the virology of EBV (Epstein-Barr Virus)?
- Enveloped dsDNA genome
- Lies latent in B cells
- Not dangerous in pregnancy
How does EBV generally present?
- Glandular fever: TRIAD (FEVER, PHARYNGITIS, LYMPHADENOPATHY) + splenomegaly + maculopapular rash
- Predisposes to Burkitt’s lymphoma
How is glandular fever diagnosed?
- Blood Film
- Monospot agglutination
- EBV Abs
How does EBV present in an immunocompromised patient?
- Post-transplant lymphoproliferative disease (predisposed to lymphoma)
What is the treatment for EBV in post-transplant lymphoproliferative disease in immunocompromised patients?
- Reduce immunosuppression
- Rituximab (anti-CD20 monclonal Ab)
What is the treatment for glandular fever?
- Supportive care
- Avoid high-contact sports
- Avoid penicillins = maculopapular rash
What is the virology of HHV 6/Roseola Virus (Human Herpesvirus 6)?
Latent in monocytes/lymphocytes
What is the clinical presentation of HHV 6 / Roseola Virus?
Roseola Infantum (Exanthum Subitum, Sixth disease)
- 3/7 fever THEN sudden maculopapular rash
- Rash starts on trunk then spreads to face + extremities
- Rarely causes encephalitis
- Most common cause: febrile convulsions
What is the route of transmission for HHV6 (Roseola Virus)?
Droplet infection
What is the management for roseola infantum?
- Sx treatment = fluids
How is roseola infantum diagnosed?
- Clinical Dx
- Blood PCR
What is the virology of HHV / Kaposi’s Sarcoma (Human Herpesvirus 8)?
- Enveloped dsDNA genome
What is the transmission of HHV8/Kaposi’s sarcoma?
Genitally
How does HHV8 present in an immunocompromised patient?
- Kaposi’s sarcoma (pathognomonic for HIV)
- Primary effusion lymphoma (a/w EBV coinfection)
- Castleman’’s disease (non-cancerous growth in LNs)
How is HHV8/Kaposi’s sarcoma treated?
- Chemoradiotehrapy
- Surgical excision
- Initiation of HAART (highly active anti-retroviral treatment) for causative HIV infection
What are the polyomaviridae viruses?
- JC virus
- BK virus
What is the virology of JC virus?
- Unenveloped dsDNA genome
How does JC virus present in an immunocompromised patient (especially AIDs)
- Progressive multifocal leukoencephalopathy
- Rapidly demyelinating disease + neurological deficits
What is the treatment for JC Virus?
Anti-retroviral therapy for HIV
What is the virology of BK virus?
- Unenveloped dsDNA genoma
How does BK virus present in an immunocompromised patient (especially post-transplant)?
- BK haemorrhagic cystitis
- BK nephropathy
What is the treatment for BK virus?
Cidofovir (cytidine analogue chain terminator)
What are the respiratory viruses?
- Influenza
- Adenovirus
- Coronavirus
What is the virology of the influenza virus?
- Enveloped, negative sense segmented genome
- 8 segments
How does the influenza virus present?
- URTI
- Systemic features inc. muscle aches
What is the treatment for the influenza virus?
- Oseltamivir (Tamiflu) = inhibits NA, blocks virion release
What is the virology of adenovirus?
Unenveloped dsDNA genoma
How does adenovirus present in an immunocompromised patient (especially transplant)?
- Encephalitis (meningoencephalitis)
- Pneuomonitis
- Colitis
- Haemorrhagic cystitis
What is the treatment for adenovirus?
- Usually self-limiting
- Supportive care in ITU/HDU
In multi-organ involvment:
- Cidofovir
- IVIG
What is the virology of coronaviruses?
- Positive sense ssRNA genomes
- Causative organisms for SARS + MERS pandemics
How does coronavirus present?
- URTI
- Sometimes has systemic infections
Severe infection can cause:
- ARDS
- Respiratory failure
- Shock
- Multi-organ dysfunction
What is the treatment for coronavirus?
- Self limiting
IF severe/hospital admission:
- Dexamethasone
- Remdesivir
What is the virology of Hep A?
- Unenveloped picornavirus
- Positive sense ssRNA genome
How does Hep A present and how is it diagnosed?
Acute Hepatitis:
- 2-6wk incubation
- Severe in elderly
- Jaundice
- Hepatitis
- Cholestasis
- Malaise
- Dx:
- Acute: Anti-HAV IgM (persists <14wks)
What is the transmission of Hep A?
Faeco-oral
What is the treatment for Hep A?
- Supportive care (resolves in 2 months)
- Vaccine (live attenuated + inactivated)
What is the virology of Hep B?
- Enveloped hepadnavirus (reversivirus)
- Hybrid genome
- Mostly DNA with an associated RNA species
What are the features of Hep B?
- Acute + chronic diseaase
- Transmission by bodily fluids: Sexual, vertical, blood products
- Virus cleared in majority of individuals (90% clearance> 5 y.o; 10% clearance in neonates)
- Lasts ~6 months
How is Hep B treated?
- Interferon α
- TENOFOVIR (nuceloTide analogue)
- Lamivudine (nuceloside analogue)
- Entecavir (nucleoside analogue)
- Telbivudine (nucleoside analogue)
What are the treatment goals for Hep B?
- Prevent progression to cirrhosis + HCC
- Maintain serum HBV DNA level as low as possible
What is the Hep B vaccine comprised of?
- Recombinant vaccine
- Purified HbSAg
What is the virlogy of Hep C?
- Enveloped flavivirus
- Positive sense ssRNA genome
What are the general features of Hep C?
- Acute + chronic disease
- Mainly blood product spread (60-80% chronicity)
- Transmission = bodily fluids + vertically
- Mostly symptomatic
What are some complications of Hep C?
- Cirrhosis
- Cryoglobulin Ax disease
- Glomerulonephritis
What are the most common Genotypes for Hep C?
Genotypes 1 (treatment less successful than 2 + 3)
How is Hep C diagnosed?
- Measure of HCV RNA (confirms infection)
What is the treatment for Hep C?
Direct Acting Antivirals = curative:
- NS3/4 protease inhibitors (-previrs) = block translation
- NS5A inhibitors (-asvirs) = block release
- Direct polymerase inhibitors -buvirs) = block replication
OR:
- Interferon α therapy
What is the virology of Hep D?
- Deltavirus
- Enveloped virus
- Negative Sense
- Single-stranded circular RNA
What are the clinical features of Hep D?
- Simultaneous co-infection with Hep B
- Superinfection (on top of) Hep B = more severe (cirrhosis in 2-3yrs)
- Transmission = sexual, parental, perinatal
What is the treatment for Hep D?
Peginterferon-α
What is the virology of Hep E?
Unenveloped positive sense SSRNA genome
What are the clinical features of Hep E?
- Acute hepatitis = India
- Faeco-oral transmission
- High risk in pregnant women
Sx:
- Jaundice
- Hepatitis
- Cholestasis
- Malaise
What are some rare complications of Hep E?
- CNS disease: Bell’s palsy, Guillain Barre, other
- Chronic infection
What is the treatment for Hep E?
- Supportive care
- Resolves in 2 months
Vaccine = recombinant HEVg1
What are some paediatric infections?
- Rubella virus
- Human parvovirus B19
- Morbillivirus
- Zika virus
What is the virology of rubella virus?
- Enveloped virus
- Positive sense ssRNA genome
How does rubella present in a child?
German Measles:
- Maculopapular rash
- Lymphadenopathy
- Fever
- Lesions on soft palate (FORCHHEIMER SIGN)
What is the treatment for rubella?
- No antiviral therapy available
- MMR VACCINE
How does congenital rubella syndrome present?
Triad: Sensorineural deafness, cataracts, heart deformity (PDA)
Ears: SENSORINEURAL DEAFNESS
Eyes: CATARACTS, glaucoma, retinopathy, microphthalmia
Heart: PDA, VSD
Neurology: microcephaly, psychomotor retardation
Pancreas: Insulin dependent DM (late)
What are the risks to rubella infection throughout pregnancy?
- <8 wks = 20% chance of spontaneous abortion
- 13-18wks = hearing defects + ?retinopathy
- > 20 wks = No documented risk
What is the virology of human parvovirus B19?
- Unenveloped
- dsDNA genome
How does human parvovirus B19 present as slapped cheek (Fifth Disease)?
- Erythema infectiosum
- Transient aplastic crisis
- Arthralgia
- Fever + malaise
What other conditions can human parvovirus B19 present as?
Viral myocarditis
How can human parvovirus B19 present congenitally?
- Foetal anaemia
- Leads to cardiac failure
- Leads to hydrops foetalis
What is the the treatment for a congenital human parvovirus B19 infection?
Intrauterine blood tranfusion
What is the virology of Morbilivirus?
- Enveloped
- Negative sense ssRNA genome
What condition is associated with Morbilivirus and how does it present?
Measles
- Fever + malaise
- Cough, coryzal Sx + conjunctivitis
- Koplik’s spots (buccal mucosa)
- Maculopapular rash
How does Morbilivirus present as a congenital infection?
- No foetal abnormalities
- Foetal loss, preterm delivery
What is the virology of zika virus?
- Enveloped falvivirus
- Positive sense ssRNA genome
How does Zika virus present congenitally?
- Severe microcephaly + skull deformity
- Decreased brain tissue, subcrotical calcification
- Retinopathy, deafness
- Talipes (feet turned in like club foot), contractures
- Hypertonia
What is the serology of Hep A?
Acute Infection:
- IgM = +ve
- IgG = -ve
Previous Infection:
- IgM = -ve
- IgG = +ve
Vaccinated:
- IgM = -ve
- IgG = +ve
What is the serology of Hep B?
Acute Infection:
- IgM = +ve
- HBsAg = +ve
- Anti-HBc = +ve
- Anti-HBs = -ve
Chronic Infection:
- IgM = -ve
- HBsAg = +ve
- Anti-HBc = +ve
- Anti-HBs = -ve
Previous Infection:
- IgM = -ve
- HBsAg = -ve
- Anti-HBc = +ve
- Anti-HBs = +ve
Vaccinated:
- IgM = -ve
- HBsAg = -ve
- Anti-HBc = -ve
- Anti-HBs = +ve
What is the serology of Hep C?
Acute Infection:
- IgG = -ve
- HCV RNA = +ve
Chronic Infection:
- IgG = +ve
- HCV RNA = +ve
Previous Infection:
- IgG = +ve
- HCV RNA = -ve
What is the serology of Hep E?
Acute Infection:
- IgM = +ve
- IgG = -ve
Previous Infection:
- IgM = -ve
- IgG = +ve
