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VIRAL INFECTIONSHerpes Simplex virus (H):FamilyHSV-1 and -2Epidemiolgoy15% women at antenatal clinic have HSV-2, 55% at STD clinicsSpreadCan be via birth canal; 1+2 both implicated in STDPathogenesisIncubation 2-12/7Replicated in skin and mms vesicular lesions; spread to sensory neurons latent infection; reactivation spread of virus from neuron to skinSymptomsMay 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 infectionHSV 1 Cold sores; blisters, Gingivostomatitis, tongue to retropharynx, herpetic whitlow; milder and less recurrent; usually not STDHSV 2 Genital herpes: vesicles superficial ulcerations; dysuria, urinary fNeonate: 40% exposed fetuses suffer serious perinatal morbidity; splenomegaly, necrotic foci in lungs, liver, adrenals, CNSPregnant: trt with acyclovir if severe 1Y genital herpes; complications = prem, abortion, IUGR, neonatal infection; acyclovir can cause fetal renal damageImmunosupp: eczema herpecticum, bronchopneumonia, hepatitis, Kaposi’s sarcoma, encephalitisOther: KeratitisHistory: sexual contactExamintion: look for evidence of other STD’sInvestigationsImmunofluorescence: 80% sens, high specViral culture: 70% sens for vesicle fluid, 25% sens for crusted lesions; 100% specPCR: high sens and specTreatmentSTD counseling; mng partners; mng other STD’s1Y 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 aboveLong term suppression: if >6 episodes/yr; decr recurrence by 70-80%; still can be infective; acyclovir 200mg BD for 6/12If disseminated: requires strict isolationGingivostomatitis: topical trt doesn’t change natural history of disease; PO hastens time to healingKeratitis: 3% acyclovir ointment 5x/day for 2/52; see ophthalmology within 24hrsNeonatal / herpes encephalitis: acyclovir 10mg/kg IV TDS for 2/52VZV (H):FamilyHerpes virus 3Epidemiology90% population have prev VZV infectionShingles: annual incidence 1:100; affects up to 50% patients >85yrsSpreadAerosol; epidemicPathogenesisInfects mms, skin, neurons chickenpox latent infection in dorsal sensory ganglia reactivates (due to decr cell mediated immunity) travels to dermatomes shingles SymptomsChickenpox (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 superinfectionShingles (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 2-4/52Herpes zoster opthalmicus: sight threateningPost-herpetic neuralgia: 10% incidence; precipitated by touch; lasts 3/12 (longer if >60yrs, triG nerve, severe, immunosupp, DM)InvestigationsSwab lesion if uncertain diagnosisTreatmentChickenpox: 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 7-10/7Shingles: 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 taperHZV opthalmicus: give acyclovir 800mg 5x/day PO 1/52; may supplement with TOP; will decr complication rate and acute pain; see ophthalmologist within 24hrsPost-herpetic neuralgia: analgesia; amitryptiline 10-25mg PO nocte, gabapentin 300mg OD, opioids, pain centre referralEBV = GLANDULAR FEVER / IMN (G)FamilyHerpes virus 4SpreadSalivaPathogenesisIn nasopharyngeal and oropharyngeal lymphoid tissues esp tonsils infection of B cells; Infects >90% humansSymptomsSymptoms primarily due to immune responseIn infants and children: asymptomatic / non-specificInfectious 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), Hodgkin’s disease (in 40-60%)) InvestigationsHeterophile ab tests – Monospot (85% sens); false –ive earlyEBV specific ab tests – IgM/G; 97% sensFBC: incr WBC, incr peri mononuclear cells, atypical lymphocytesLFTs – incr AST/ALTTreatmentSupportiveCytomegalovirus (G)FamilyHerpes virus 5SpreadTransplacental; breast milk; saliva; veneral, resp secretions and fecal-oral in teenagers (infected people secrete virus in body secretions for months); organ transplants and blood transfusionsPathogenesisInfects and latent in WBC; can be reactivated; asymptomatic excretion persists for yearsSymptomsUsually asymptomatic in healthy / glandular fever-like illness (fever, atypical lymphocytosis, lympadenopathy, Hepatomegaly, abnormal LFT’s)Serious in neonates and immunocompromisedCongenital – 95% asymptomatic; may get cytomegalic inclusion disease (IUGR, jaundice, hepatosplenomegaly, anaemia, bleeding, thrombocytopenia, encephalitis, hearing loss, pneumonitis, hepatitis); similar to toxoplasmosisPerinatal – usually asymptomatic; pneumonitis, FTT, rash, hepatitisIn immunosuppressed –reactivation of latent virus; pneumonitis, colitis, retinitis, renal dysfunctionInvestigationsAntibodies; urine cultureTreatmentSupportiveIf life / sight-threatening – ganciclovir (may be used as prophylaxis in advanced HIV)Prophylactic acyclovir in post-tranplantToxoplasmosis (G)FamilyToxoplasma gondii; obligatory intracellular protozoanSpreadTransplacental; undercooked meat; contaminated soil (cats)RF: immunocompromise, congenital transmissionPathogenesisTissue cysts form in cat’s intestines; oocytes shed in cat’s faecesSymptomsOften asymptomaticCongenital: 50% risk of fetal effects in maternal infection; miscarriage, chronic chorioretinitis; severe jaundice, hepatosplenomegaly, thrombocytopenic purpura, seizures, hydrocephalus, mental retardationAcquired: usually asymptomatic / benign; infectious mononucleosis-like; posterior uveitisImmunocompromised: rash, fever, rigors, encephalitis, hepatitis, pneumonia, myocarditis; acute severe infection in 40% AIDS patientsInvestigationsIgM – in first 1-2/52; peak 4-8/52IgG – slow rise; peak 4-8/52; remain for yearsAb’s less useful in immunocompromisedCT/MRI – ring enhancing lesions; oedema in basal ganglia / cortico-medullary junctionTreatmentTreat if: neonate, pregnancy (beware if 1st trim, sulphonamides cause congenital abnormalities, but so does toxoplasmosis), immunocompromised, organ dysfunction, persisitent severe SxPyrimethamine 25-50mg/day for 3-4/52Give folate to prevent haematological toxicityIf cerebral in AIDS: sulfadiazine 1 – 1.5g IV Q6hrly + pyrimethamineDispositionPoor prognosis if fetal 1st trimester; good if 3rd trim or post-natal; often fatal in immunocompromisedMeasles – see paedsMumpsFamilyParamyxovirusSpreadResp dropletsPathogenesisSpread to LN’s in lymphoctes blood glandsSymptomsSalivary gland pain and swelling; can spread to CNS (aseptic meningitis), testis, ovary, pancreasInvestigationTreatmentDispositionPoliovirusFamilyEnterovirusSpreadFaecal-oralPathogenesisOropharynx multiplies in intestinal mucosa and LN, transient viraemia and fever CNS via bloodSymptomsAsymptomatic usually; 1/100 invade CNS motor neuron of SC / brainsteam flaccid paralysisInvestigationTreatmentOnly briefly shed; fecal-oral routeDispositionViral Haemorrhagic FeversFamilyAdenavirus, filovirus, flavivirusSpreadInsect hostPathogenesisEndothelial cell infection; Neutropenia, low plt, severe plt dysfunction, endothelial dysfunction, incr vascular permeability; necrosis and hameorrhage of organs; DICSymptomsFever, haemorrhag,e headache, myalgia, rash shockInvestigationTreatmentSupportiveDispositionHPVFamilyPapovavirusSpreadSkin and genital contactPathogenesisInfect epithelial cellsSymptomsWarts, benign squamous tumours, SCC cervix and anogenitalInvestigationTreatmentSkin and genital contactDispositionNorovirusFamilySpreadContact; food; commonest food-bourne viral infectionPathogenesisSymptomsOnset 12-24hrs; D+V; offset 2/7InvestigationsTreatmentDispositionRotavirusFamilySpreadContact; faecal contamination of food; commonest cause of food poisoning in infantsPathogenesisSymptomsV; watery D; feverInvestigationsTreatmentDispositionVIRAL INFECTIONSObligate 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)PathogenFamilyGenomic TypePresentationRespiratoryAdenovirusAdenoviridaeDS DNAURTI, LRTI, conjunctivitis, diarrhoeaRhinovirusPicornaviridaeSS RNAURTICoxsackievirusPleurodynia, herpangina, hand-foot-and-mouth disease, SARSCoronavirusCoronaviridaeURTIInfluenza A+BOrthomyxoviridaeInfluenzaRSVParamyxoviridaeBronchiolitis, pneumoniaDigestiveMumpsParamyxoviridaeSS RNAMumps, pancreatitis, orchitisNorwalk agentCaliciviridaeGastroenteritisHep APicornaviridaeAcute hepatitisHep DViroid-likeAcute/chronic hepatitisHep CFlaviviridaeEnterically transmitted hepatitisHep ENorwalk-likRotavirusReoviridaeDS RNADiarrhoeaHep BHepadnaviridaeDS DNAAcute / chronic hepatitisSystemic with skin eruptionMeaslesParamyxoviridaeSS RNAMeaslesRubellaTogaviridaeGerman measlesParvovirusParvoviridaeSS DNAErythema infectiosum, asplastic anaemiaVacciniaPoxviridaeDS DNASmallpox vaccineVZVHerpesviridaeChickenpox, shinglesHSV 1Cold soreHSV 2Genital herpesSystemic with haematopoietic disorderCMVHerpesviridaeDS DNACytomegalic inclusion diseaseEBVInfectious mononucleosisHTLV-1RetroviridaeSS RNAAdult T-cell leukaemia, tropical spastic paraparesisHIV-1 and 2AIDSArboviral and haemorrhagic feversDengue virus 1-4TogaviridaeSS RNADengue, haemorrhagic feverYellow fever virusYellow feverRegional haemorrhagic feverFiloviridae / hantavirusEbola, Manburg diseaseWarty GrowthsPapillomavirusPapovaviridaeDS DNACondyloma, cervical CaCNSPoliovirusPicornaviridaeSS RNAPoliomyelitisJC virusPapovaviridaeDS DNAProgressive multifocal leukoencephalopathyArboviral encephalitisTogaviridaeSS RNA ................
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