VIRAL INFECTIONS
Herpes Simplex virus (H):
Family
HSV-1 and -2
Epidemiolgoy
15% women at antenatal clinic have HSV-2, 55% at STD clinics
Spread
Can be via birth canal; 1+2 both implicated in STD
Pathogenesis
Incubation 2-12/7
Replicated in skin and mms  vesicular lesions; spread to sensory neurons  latent infection; reactivation  spread of virus from neuron to skin
Symptoms
May interchange sites; cannot differentiate 1 and 2 clinically; painful, recurrent, preceded by burning/numbness  clustered vesicles, blistering, crusting;
recurrence precipitated by stress, menstruation, ill health; heal over 2/52; may get 2Y bacterial infection
HSV 1  Cold sores; blisters, Gingivostomatitis, tongue to retropharynx, herpetic whitlow; milder and less recurrent; usually not STD
HSV 2  Genital herpes: vesicles  superficial ulcerations; dysuria, urinary f
Neonate: 40% exposed fetuses suffer serious perinatal morbidity; splenomegaly, necrotic foci in lungs, liver, adrenals, CNS
Pregnant: trt with acyclovir if severe 1Y genital herpes; complications = prem, abortion, IUGR, neonatal infection; acyclovir can cause fetal renal damage
Immunosupp: eczema herpecticum, bronchopneumonia, hepatitis, Kaposi’s sarcoma, encephalitis
Other: Keratitis
History: sexual contact
Examintion: look for evidence of other STD’s
Investigations
Immunofluorescence: 80% sens, high spec
Viral culture: 70% sens for vesicle fluid, 25% sens for crusted lesions; 100% spec
PCR: high sens and spec
Treatment
STD counseling; mng partners; mng other STD’s
1Y genital: antivirals  decr duration of shedding, decr time to crusting and healing, decr duration of constitutional Sx, decr local pain; always trt 1Y
illness; acyclovir 400mg PO TDS for 5/7 (4-10x more sens to acyclovir than VZV)
Recurrent genital: recommended if start within 72hrs Sx onset; same as above
Long term suppression: if >6 episodes/yr; decr recurrence by 70-80%; still can be infective; acyclovir 200mg BD for 6/12
If disseminated: requires strict isolation
Gingivostomatitis: topical trt doesn’t change natural history of disease; PO hastens time to healing
Keratitis: 3% acyclovir ointment 5x/day for 2/52; see ophthalmology within 24hrs
Neonatal / herpes encephalitis: acyclovir 10mg/kg IV TDS for 2/52
Family
Herpes virus 3
Epidemiology
90% population have prev VZV infection
Shingles: annual incidence 1:100; affects up to 50% patients >85yrs
Spread
Aerosol; epidemic
Pathogenesis
Infects mms, skin, neurons  chickenpox  latent infection in dorsal sensory ganglia  reactivates (due to decr cell mediated immunity)  travels to
dermatomes  shingles
Symptoms
Chickenpox (varicella zoster); mild in children, severe in adults and immunocompromised; rash 2 weeks after resp infection; may rarely cause interstitial
pneumonia, encephalitis, transverse myelitis necrotising visceral lesions; Macule  vesicle  rupture  crust  heal with no scars unless bacterial
superinfection
Shingles (herpes zoster): usually occurs only once in immunosuppressed / elderly; rarely geniculate nucleus invovled --> Ramsay-Hunt syndrome, with
facial paralysis; prodrome (pain, burning, headache, malaise) precedes rash by 2-3/7  dermatomal rash, vesicles at 3-5/7, crusts at 7-10/7, heals in 2-4/52
Herpes zoster opthalmicus: sight threatening
Post-herpetic neuralgia: 10% incidence; precipitated by touch; lasts 3/12 (longer if >60yrs, triG nerve, severe, immunosupp, DM)
Investigations
Swab lesion if uncertain diagnosis
Treatment
Chickenpox: can give vaccine / Ig to exposed contacts; no different in pregnancy; highest risk if fetus infected 13-20/40 (only occurs in 2% non-immune
women)  IUGR, cutaneous scarring, limb hypoplasia, cerebral cortical atrophy; if immunocomp, 5-20% risk of death
Antivirals if: immunocomp; causes decr pain and fever, decr risk of dissemination and decr time to healing; given 10mg/kg acyclovir TDS for 7-10/7
Shingles: isolate from high risk patients until lesions dry (eg. <1yrs, immunosupp, preg); saline baths TDS; analgesia
Antivirals if: ophthalmic, immunocomp, >50yrs, <72hrs since onset; decr no vesicles, decr time to resolution, decr duration post-herpetic neuralgia;
acyclovir 800mg 5x/day 1/52
Steroids: may help analgesia; give if >50yrs; 50mg pred OD 1/52 then taper
HZV opthalmicus: give acyclovir 800mg 5x/day PO 1/52; may supplement with TOP; will decr complication rate and acute pain; see ophthalmologist
within 24hrs
Post-herpetic neuralgia: analgesia; amitryptiline 10-25mg PO nocte, gabapentin 300mg OD, opioids, pain centre referral
Family
Herpes virus 4
Spread
Saliva
Pathogenesis
In nasopharyngeal and oropharyngeal lymphoid tissues esp tonsils  infection of B cells; Infects >90% humans
Symptoms
Symptoms primarily due to immune response
In infants and children: asymptomatic / non-specific
Infectious mononucleosis – benign, self-limited; lymphoproliferative disorder; >50% have fever, LN’s and pharyngitis; 70-90% get morbilliform rash with
amoxycillin; Splenomegaly (>10%; may get rupture), hepatomegaly (>10%), meningoencephalitis / GBS, pneumonitis, palatal petechaie, myocarditis,
pancytopenia --> resolves in 4-6/52; Hairy leukoplakia, neoplasms (eg. Burkitt lymphoma (>90%), nasopharyngeal Ca (nearly 100% 2Y to EBV),
VZV (H):
EBV = GLANDULAR FEVER / IMN (G)
Hodgkin’s disease (in 40-60%))
Investigations
Heterophile ab tests – Monospot (85% sens); false –ive early
EBV specific ab tests – IgM/G; 97% sens
FBC: incr WBC, incr peri mononuclear cells, atypical lymphocytes
LFTs – incr AST/ALT
Treatment
Supportive
Family
Herpes virus 5
Spread
Transplacental; breast milk; saliva; veneral, resp secretions and fecal-oral in teenagers (infected people secrete virus in body secretions for months); organ
transplants and blood transfusions
Pathogenesis
Infects and latent in WBC; can be reactivated; asymptomatic excretion persists for years
Symptoms
Usually asymptomatic in healthy / glandular fever-like illness (fever, atypical lymphocytosis, lympadenopathy, Hepatomegaly, abnormal LFT’s)
Serious in neonates and immunocompromised
Congenital – 95% asymptomatic; may get cytomegalic inclusion disease (IUGR, jaundice, hepatosplenomegaly, anaemia, bleeding, thrombocytopenia,
encephalitis, hearing loss, pneumonitis, hepatitis); similar to toxoplasmosis
Perinatal – usually asymptomatic; pneumonitis, FTT, rash, hepatitis
In immunosuppressed –reactivation of latent virus; pneumonitis, colitis, retinitis, renal dysfunction
Investigations
Antibodies; urine culture
Treatment
Supportive
If life / sight-threatening – ganciclovir (may be used as prophylaxis in advanced HIV)
Prophylactic acyclovir in post-tranplant
Family
Toxoplasma gondii; obligatory intracellular protozoan
Spread
Transplacental; undercooked meat; contaminated soil (cats)
RF: immunocompromise, congenital transmission
Pathogenesis
Tissue cysts form in cat’s intestines; oocytes shed in cat’s faeces
Symptoms
Often asymptomatic
Congenital: 50% risk of fetal effects in maternal infection; miscarriage, chronic chorioretinitis; severe jaundice, hepatosplenomegaly, thrombocytopenic
purpura, seizures, hydrocephalus, mental retardation
Acquired: usually asymptomatic / benign; infectious mononucleosis-like; posterior uveitis
Immunocompromised: rash, fever, rigors, encephalitis, hepatitis, pneumonia, myocarditis; acute severe infection in 40% AIDS patients
Investigations
IgM – in first 1-2/52; peak 4-8/52
IgG – slow rise; peak 4-8/52; remain for years
Ab’s less useful in immunocompromised
CT/MRI – ring enhancing lesions; oedema in basal ganglia / cortico-medullary junction
Treatment
Treat if: neonate, pregnancy (beware if 1st trim, sulphonamides cause congenital abnormalities, but so does toxoplasmosis), immunocompromised,
organ dysfunction, persisitent severe Sx
Pyrimethamine 25-50mg/day for 3-4/52
Give folate to prevent haematological toxicity
If cerebral in AIDS: sulfadiazine 1 – 1.5g IV Q6hrly + pyrimethamine
Disposition
Poor prognosis if fetal 1st trimester; good if 3rd trim or post-natal; often fatal in immunocompromised
Cytomegalovirus (G)
Toxoplasmosis (G)
Measles – see paeds
Mumps
Family
Paramyxovirus
Spread
Resp droplets
Pathogenesis
Spread to LN’s in lymphoctes  blood  glands
Symptoms
Salivary gland pain and swelling; can spread to CNS (aseptic meningitis), testis, ovary, pancreas
Investigation
Treatment
Disposition
Poliovirus
Family
Enterovirus
Spread
Faecal-oral
Pathogenesis
Oropharynx  multiplies in intestinal mucosa and LN, transient viraemia and fever  CNS via blood
Symptoms
Asymptomatic usually; 1/100 invade CNS  motor neuron of SC / brainsteam  flaccid paralysis
Investigation
Treatment
Only briefly shed; fecal-oral route
Disposition
Viral Haemorrhagic Fevers
Family
Adenavirus, filovirus, flavivirus
Spread
Insect host
Pathogenesis
Endothelial cell infection; Neutropenia, low plt, severe plt dysfunction, endothelial dysfunction, incr vascular permeability;
necrosis and hameorrhage of organs; DIC
Symptoms
Fever, haemorrhag,e headache, myalgia, rash  shock
Investigation
Treatment
Supportive
Disposition
HPV
Family
Papovavirus
Spread
Skin and genital contact
Pathogenesis
Infect epithelial cells
Symptoms
Warts, benign squamous tumours, SCC cervix and anogenital
Investigation
Treatment
Skin and genital contact
Disposition
Norovirus
Family
Spread
Contact; food; commonest food-bourne viral infection
Pathogenesis
Symptoms
Onset 12-24hrs; D+V; offset 2/7
Investigations
Treatment
Disposition
Rotavirus
Family
Spread
Contact; faecal contamination of food; commonest cause of food poisoning in infants
Pathogenesis
Symptoms
V; watery D; fever
Investigations
Treatment
Disposition
VIRAL INFECTIONS
Obligate intracellular parasites that depend on host cell's metabolic machinery for replication; nucleic
acid genome surrounded by protein coat (capsid) that may be encased in lipid membrane; can be latent
(eg. Herpes zoster in dorsal root ganglia); may transform host cell into tumour (eg. HPV)
Pathogen
Family
Genomic Type
Presentation
Adenovirus
Adenoviridae
DS DNA
URTI, LRTI, conjunctivitis, diarrhoea
Rhinovirus
Picornaviridae
Respiratory
Coxsackievirus
URTI
SS RNA
Pleurodynia, herpangina, hand-foot-and-mouth disease, SARS
Coronavirus
Coronaviridae
URTI
Influenza A+B
Orthomyxoviridae
Influenza
RSV
Paramyxoviridae
Bronchiolitis, pneumonia
Mumps
Paramyxoviridae
Mumps, pancreatitis, orchitis
Norwalk agent
Caliciviridae
Gastroenteritis
Hep A
Picornaviridae
Digestive
Acute hepatitis
SS RNA
Hep D
Viroid-like
Acute/chronic hepatitis
Hep C
Flaviviridae
Hep E
Norwalk-lik
Rotavirus
Reoviridae
DS RNA
Diarrhoea
Hep B
Hepadnaviridae
DS DNA
Acute / chronic hepatitis
Enterically transmitted hepatitis
Systemic with skin eruption
Measles
Paramyxoviridae
Rubella
Togaviridae
Parvovirus
Parvoviridae
Vaccinia
Poxviridae
VZV
HSV 1
Herpesviridae
SS RNA
SS DNA
Measles
German measles
Erythema infectiosum, asplastic anaemia
Smallpox vaccine
DS DNA
HSV 2
Chickenpox, shingles
Cold sore
Genital herpes
Systemic with haematopoietic disorder
CMV
EBV
HTLV-1
HIV-1 and 2
Herpesviridae
DS DNA
Retroviridae
SS RNA
Cytomegalic inclusion disease
Infectious mononucleosis
Adult T-cell leukaemia, tropical spastic paraparesis
AIDS
Arboviral and haemorrhagic fevers
Dengue virus 1-4
Yellow fever virus
Dengue, haemorrhagic fever
Togaviridae
SS RNA
Regional
Filoviridae /
haemorrhagic fever hantavirus
Yellow fever
Ebola, Manburg disease
Warty Growths
Papillomavirus
Papovaviridae
DS DNA
Condyloma, cervical Ca
Poliovirus
Picornaviridae
SS RNA
Poliomyelitis
JC virus
Papovaviridae
DS DNA
Progressive multifocal leukoencephalopathy
Arboviral
encephalitis
Togaviridae
SS RNA
CNS