Viral infections Flashcards

Question

Erythema chronicum migrans

Answer 1

Erythema chronicum migrans | Lyme disease

Answer 2

* All except mumps are characterised by feverand generalised rash * Highly infectious - >90% infected in childhood * Lifelong immunity following natural infection * Childhood infection _ occasional complications * Adult infection - more often severe, complicated

Answer 3

``` • Peak incidence in 5-9y (pre-vax era) • Incubation period:15-24d • 30% sub-clinical • Clinical mumps – Non-specific prodrome x 1-2 d – Unilateral → bilateral parotid swelling/tenderness. • Complications – Orchitis in 20% postpubertal young – Oophoritis in 5% – Aseptic meningitis in 15% – Rarely encephalitis, permanent unilateral deafness ```

Answer 4

•Highly infectious: R0 = 11-14 •Eliminated from some countries •Developed countries: peak incidence in 3-5 year olds (pre-MMR) •Developing countries: high incidence in <2y, high fatality rate Clinical features • Incubation period 10-14 days. • Prodromal symptoms – coryza and conjunctivitis, Koplik’s spots in the buccal mucosa. • Fever (40C) and maculopapular rash. Rash appears first on the face and spreads to the trunk and limbs within 2 days. • Complications: pneumonia (bacterial or viral) encephalitis • High morbidity and mortality in the immunocompromised host

Answer 5

Rubella and Its Complications • Mild illness with fine red maculopapular rash in childhood. • Arthralgia/arthritis in ~60% adult women. • Infection in first trimester of pregnancy - Congenital rubella syndrome

Answer 6

• Causes mild illness “slapped cheek syndrome” in young school children. Fine rash. • Like rubella causes arthropathy in women • Virus infects nucleated red cells → sig. anaemia in immune compromised. Rx IVIg → aplastic crisis in haemolytic anaemia → fetal infection may cause hydrops fetalis due to heart failure. Treated by intruterine transfusion • No vaccine available

Answer 7

* Identical on Electron microscopy (fried egg) * Large double-stranded DNA genome * Icosahedral capsid * Lipid envelope

Answer 8

Classification • Over 100 herpesviruses have been identified • Biological properties and genomic structure ®Sub-families alpha-, beta-, gamma- herpesvirinae • Viruses of each species are numbered in chronological order of discovery • Eight human herpes viruses have been identified to date

Answer 9

* During lytic infection, host cells are productively infected. New virions ®cell lysis. * After primary infection, viruses are not eradicated but persist by establishing latent infection in host cells, when no new virions are made * Latency genes may be expressed. * Reactivation of virus may occur, with production of infectious virions

Answer 10

* Primary infections are frequently asymptomatic * Virus is not cleared but persists in a latent state * Reactivation may be clinical or sub-clinical * Infection is usually widespread in the natural host

Answer 11

* Seropositive status indicates infection, not immunity * Cell-mediated responses are critical in controlling infection * Both primary and recurrent infection threaten individuals with defective cell mediated immunity * Anti-viral agents, e.g. Aciclovir, Ganciclovir can control productive herpes virus infections but cannot eradicate/control latent infection

Answer 12

Clinical Features • Incubation period 10-21d • Asymptomatic infection uncommon • Prodromal symptoms: fever, pharyngitis, malaise • Itchy/painful lesions appear in crops • Macules -papules - vesicles - pustules - crusts • Virus is not cleared following primary infection but establishes latency in sensory dorsal root and cranial nerve ganglia • More severe in adults / immunocompromised • Maternal varicella - risk of congenital/neonatal varicella • Varicella vaccine is a live attenuated vaccine, now licensed in UK

Answer 13

Clinical Features • Reactivation of latent VZV • Pain at site may precede eruption of painful vesicles • Unilateral; 1-2 unilateral dermatomes involved • Thoracic in >50% cases • Ophthalmic division trigeminal nerve - eye in 50% • Immunocompetent rarely suffer > 2 attacks/lifetime • Post-herpetic neuralgia especially in the elderly • Incidence PHN increases with age and in the i.c. host

Answer 14

• HSV1 and HSV2 are distinct serotypes • Painful vesicular lesions • Latent infection of sensory ganglia by retrograde spread • Primary infection and reactivation frequently asymptomatic • Multiple symptomatic recurrences may occur in immunocompetent individuals • More severe in immunocompromised host

Answer 15

``` Pirmarily HSV 1 • Transmitted by salivary contact • 10 infection -fever & gingivostomatitis • Recurrent oral herpes > cold sores • Can spread to other areas of skin, eye – Herpetic whitlow, – Eczema herpeticum, – Corneal ulceration • Herpes encephalitis can occur at any age -usually due to HSV1 reactivation ```

Answer 16

Typically HSV 2 • Sexually transmitted disease, HSV1 increasingly common • Primary/initial infection may cause constitutional illness with fever, aseptic meningitis/ urinary retention • Multiple painful ulcers on genitals/adjacent skin +/- urethritis cystitis cervicitis proctitis • Recurrent attacks less severe • Lifelong viral shedding regardless of symptoms • Risk of neonatal herpes • Genital HSV increase risk of HIV transmission • Control of troublesome recurrences: prophylaxis or pre-emptive Rx ``` Detection of primary/ reactivated HSV/VZV in skin lesions: •Electron microscopy •Immunofluorescence •Tissue culture •PCR ```

Answer 17

* Aciclovir * Valaciclovir→aciclovir * Famciclovir→penciclovir

Answer 18

* Ganciclovir * Valganciclovir → ganciclovir * Foscarnet * Cidofovir

Answer 19

• Adult seroprevalence 50% (1% pa) • Congenital infection in <1% – majority asymptomatic • Occasional cause of “glandular fever” / mononuclear syndrome • Life-threatening disease in patients with defective cellular immunity – AIDS – Bone marrow Tx – Organ Tx recipients Not associated with malignancies

Answer 20

• Adult seroprevalence 95% • Primary infection sub-clinical in childhood • Symptomatic in 50% adolescents/young adults Infectious mononucleosis “kissing disease” – fever – lymphadenopathy – pharyngitis • Cause/co-factor in several malignancies inc Burkitts lymphoma Nasopharyngeal carcinoma Hodgkin Disease HIV-associated lymphoma Post Transplant lympohoproliferative disease

Answer 21

features suggestive of infectious mononucleosis including fever, pharyngitis lymphadenopathy • “Mononuclear syndrome” – means that increased mononuclear cells ( lymphocytes and/or monocytes) are present in the peripheral blood • Several possible aetiologies depending on age, clinical setting, travel etc • In the teenager, young adult in UK first consider: – Primary infection with EBV, CMV or toxoplasma gondii – HIV seroconversion – Streptococcal throat infection

Answer 22

* Enteroviruses (including polio) * Mumps virus * Herpes simplex viruses (genital herpes) * HIV seroconversion illness * Other herpes viruses eg varicella zoster virus * Epstein Barr virus

Answer 23

* Epidemiology suggested Kaposi’s sarcoma (KS) caused by a sexually transmitted agent * HHV-8 sequences identified in KS (1993) * Gamma herpes virus * No recognised illness associated with primary infection * Encodes oncogenes * HHV-8 is present in KS tumour cells * Primary effusion lymphomas (PELs) * Castleman’s disease in AIDS

Answer 24

- requires modified diagnostic skills - • The usual cardinal features may be absent eg no fever or rash • More than one cause - not necessarily a single unifying diagnosis • Agents of acute infection may cause chronic disease • Delayed/absent serological responses • Interpretation of serology complicated by passive acquisition of AB in blood/blood products • “Timetable” modified by prevention strategies

Answer 25

Headache Photophobia Vomiting +/-Neck stiffness •No LOC. No Δ behaviour. No Δ intellectual function. •Patient appears generally well – unlike bacterial meningitis. •Benign self-limiting condition •Mild pleocytosis – Predominantly lymphocytes Aetiology: •Enteroviruses (including polio) •Mumps virus •HSV (genital herpes) , EBV, VZV •HIV seroconversion illness

Answer 26

Non-enveloped RNA viruses Faecal-oral spread → lymphoid tissue → viraemia Vast majority of infections asymptomatic Potential for CNS invasion and neurological disease Neurological Manifestations: •Aseptic meningitis •Meningoencephalitis •Paralytic poliomyelitis

Answer 27

* Complicates 10% cases with parotitis * 50% cases occur in absence of any parotid swelling * Presents before, during or after parotid swelling * Usually CSF lymphocytosis, ↑protein, normal glucose but ↑ polys, low glucose can confuse picture * 10 day illness with complete recovery as a rule * Subclinical CNS infection is common * CSF Pleocytosis present in 50% mumps cases without meningitis

Answer 28

•Distinct from HSV encephalitis •Complication of primary genital herpes (HSV2 or HSV1) •↑frequency due to HSV’s changing epidemiology •NB Enquire re genital symptoms More common in females •Implicated in Mollaret’s meningitis

Answer 29

meningoencephaltis/encephalomyelitis Clinical features c/w brain tissue disease •Altered personality/behaviour (ΔMS) •Seizures •Focal neurological signs Risk of permanent disability or death. Inflammatory cells may be present in CSF ``` Aetiology: •Herpes simplex •Enteroviruses (including polio) •Varicella zoster virus Travel-related: •Rabies •Arthropod-borne “Arboviruses” –eg West Nile virus •Post-infectious (ADEM) ```

Answer 30

* Commonest sporadic cause of encephalitis * Usually HSV1, recurrent or primary * HSV spreads to brain, esp temporal lobe * Usually no associated HSV skin lesions * Untreated → 70% mortality; neuro sequelae * Early aciclovir Rx →↓ morbidity/mortality * High index of suspicion → empiric Rx until Dx ruled out * Beware false negative HSV on PCR

Answer 31

•Zoonosis – man is incidental host •Endemic in wild mammals in many countries •Transmission via bite from infected animal •Neuronal spread: bite → CNS → salivary glands → limbic system → aggression → t/m by bite •Incubation period reflects site of bite (4w-6m) •Human cases “Paralytic” or “dumb” Rx and prevention: c 0% survival •National animal importation policies , Vaccination of pets and wild animals • Routine prophylaxis: vaccine •Post-exposure vaccine: vaccine + immune globulin

Answer 32

ACUTE DEMYELINATING ENCEPHALOMYELOPATHY - ADEM •Clinical features suggest acute encephalitis -but no infectious agent or local antibody response in the CNS. •Auto-immune phenomenon •Systemic infection→demyelination & inflammation. * White cells and protein may be present in the CSF * Diagnosis of exclusion * complication following measles, mumps, rubella, varicella zoster virus infections

Answer 33

POLIOMYELITIS • Infrequent complication of poliovirus infection •Asymp –aseptic meningitis •Poliomyelitis develops in 1%: Infection of anterior horn cells →flaccid paralysis → Respiratory failure (bulbar) •Now eliminated from most countries.WHO targets eradication

Answer 34

``` TB meningitis* •Cerebral malaria •Spongiform encephalopathy (eg vCJD) •SSPE – measles virus –Sub-acute sclerosing panencephalitis * More common in immunocompromised host ```

Answer 35

``` Opportunistic CNS Infections •HIV encephalopathy •Primary CNS lymphoma/PTLD (EBV) •CMV Encephalitis •Progressive multifocal leukoencephalopathy (JV virus) •Cryptococcus neoformans** meningitis •Cerebral toxoplasmosis •Nocardia •Aspergillus ```