Lectures 45 & 46 SBM

Question 1

(English) measles aka rubeola virus characteristics

Answer 1

• paramyxovirus, genus=mobillivirus
• important proteins: hemagluttinin, matrix protein, fusion protein
• Transmission: contagious 5 d before and 4 dafter rash
• Incubation; 7 to 18 d

Etiopath:

• site of replication: respiratiory epithelium
• 4 d viremia seeds: lymphoid, skin, and other organs
• syncytial formation

Sx: 3 C -> Cough, Coryza, Conjunctivitis;

• Koplik’s spot,
• lymphadenopathy,
• maculopapular rash on face, chest, palms; Face -> spreads downward
• Assoc sx: photophobia

Complications:

• encephalitis
• interstitial pneumonia
• bacterial superinfections: pneumonia, otitis media
• Subacute Scleroising Panencephalitis (SSPE) -> death years later.

Dx: urine or pharyngeal cell specimens

• PCR
• culture on monkey kidney cells useful for epi studies
• Immunological

Control: live attenuated virus + 2nd dose = lifelong immunity (don’t give to pregnant and younger than 13 mo)

• Note: lapse in vaccination leads to disease (Alaska) -> virus could not assemble and body could not clear it -> get to brain -> encephalitis -> child’s behaviour changes and grades drop off

Question 2

Rubella (German measles) characteristics

Answer 2

• “little red” – mild measles
• Togavirus, one serotype, human reservoir only
• Transmission: 7 days contagious before and after rash
• Incubation: 14 to 21 d

Etiopath: 2 main transmission

• Airborne transmission
• transplacental spread to fetus (more serious):
  
  • chronic fetal infection
  • compromised fetal oxygenation
  • disruption of nl organogenesis (impaired mitosis, cell necrosis, chromosomal breakage)
• immune complexes, tissue damage, shed virus for years

Sx: overall a mild disease usually; complications rare

• lymphadenopathy
• maculopapular rash/exanthem also starts on face , neck, and trunk @ d1-2 prodromal to fever lasting 1 to 3 d
• palatial spots @ d1; NO Koplik’s spots

Complications: transient arthritis, transient althralgia, encephalitis

• real worry is congenital infection -> highest risk in 1st trimester; no major risk to fetus after 5 mo
  
  • cardiac defects
  • nerve deafness
  • eye defects -> cataracts in infants
  • microcephaly
  • encephalitis
  • hepatosplenomegaly
  • thrombocytopenia
  • intrauterine growth retardation
  • complications: hepatitis, anemia, interstitial pneumonia, DIC, diabetes, chronic thyroiditis, SSPE

Dx:

• PCR of respiratory secretions
• serology
• congenital infections -> titer comparison
• Control: live vaccine

Question 3

B19 characteristics

Answer 3

• unenveloped ssDNA
• Transmission: spread by respiratory droplets, Pt infectious for 1 wk
• Incubation 4 to 12 days

Etiopath: replicates in nucleus of RBC and synovial cells

• causes arrest in erythropoiesis for 7 to 10 d
• aplastic crisis for thalassemia, Sickle-cell, HIV + (Acute polyarthritis in adults)
• chronic anemia for immature immune system (fetus) & deficient immune system
• congenital infection -> hydrops fetalis
• Epi: focal outbreaks during spring

Sx: 5th disease

• slapped cheek called erythema infectiosum
• also affects arms & legs
• fever, headache & myalgia
• itching
• lymphadenopathy, leukopenia, anemia
• arthralgia/arthritis later in females
• illness lasts 1 to 4 wk

Dx:

• PCR of blood
• culture not used
• serology

Rx:

• transfusion of packed RBC for anemia
• no specific antiviral therapy
• Control: no vaccine

Question 4

Other causes of Rubella-like rashes

Answer 4

• 17 ECHO virus
• 9 Coxsackie viruses
• adenovirus
• arbovirus such as Dengue
• Epstein-Barr virus
• Scarlet fever
• toxic drug eruptions
• others

Question 5

Hand foot and mouth disease

Answer 5

• Cause: enterovirus/Coxsackie A16; common viral illness of children
• Note: disease NOT related to hoof-and-mouth disease of cattle
• Rx: none

Question 6

Roseola Infantum syndrome

Answer 6

• Cause: HHV-6B -> 6th disease
• Etiopath: HHV-6 is a T-cell lymphotropic virus; 2 strains
  
  • HHV-6b: infects babies < 20 YO
  • HHV-6a: infects adults, found in LN of AIDS Pt
• Sx: abupt onset
  
  • high-grade fever
  • convulsions (sometimes)
  • leukopenia
  • 3 to 5 d later -> fever subsides then rose-pink maculopapular rash
  • Complications: liver, lung, CNS
• Rx: Cidofovir & ganciclovir

Question 7

HHV-1

Answer 7

• 3 major syndromes of HHV-1
  
  • Herpes labialis: most common form of infection
    
    • recurrent (reactivation) infection, localised to lips (cold-sores)
    • fades over 4 to 5 d; if prolonged -> pustular forms, crusting and healing in 8 to 10 d leaving no scars
  • Eczema herpeticum: only in Pt w skin disorders -> cutaneoous infections severe and widespread (otherwise intact skin resistant to HHV-1 & 2)
  • Gingivostomatitis: 1o infection often occurs in children age 1 to 5 yo.
    
    • Transmission: blood-borne
    • Incubation: 3 to 5 d, disease lasting 2 to 3 wk
    • Sx: fever, sore throat, mouth inflammation, submandibular lymphadenopathy, malaise, vesicular & ulcerative lesions, edema

Question 8

HHV-2

Answer 8

• Transmission: infections of baby in pre natal and post natal period
  
  • Pre: transplacental causes malformations similar to rubella
  • Post: 75% infections via birth canal causes 50% mortality, survivors w neuro impairment
• Dx: for both HHV-1 & 2
  
  • PCR of skin, organ, saliva specimen

Question 9

CMV in the immunocompromised

Answer 9

• AIDS Pt: devastating infection; retinitis, colitis, pneumonia
• Leukemia and lymphoma Pt at high risk of CMV complications
• Dx: transplant and donor should be dx and screened
  
  • PCR using whole blood

Question 10

HHV-8

Answer 10

• Kaposi’s sarcoma (KS); assoc w HIV+
• Affects CT, bone, fat, muscle, and blood vessels.
• Dx: punch bipsy for KS cell microscopy

Question 11

Varicella Zoster HHV-3

Answer 11

• not a true pox virus (pox virus: blood & organ component
• not a rash)
• Transmission: respiratory secretions; reservoir is infected person; spread by contact or aerosol
  
  • communicable from 5 d before eruption of pox and 6 d after last crop of vesicles
• Incubation: 10 to 23 d
• Etiopath: virus enters RT
  
  • virus carried by phagocytic cells to local LN for 1o replication (some 1o replication may occur in RT)
  • virally-infected cells into capillaries
  • 1o viremia -> replication in liver/spleen and other reticuloendothelial sites
  • 2o viremia -> mononuclear cells transport virus to skin and mucous membranes
  • virus release into resp. secretions
  • replication in epidermal cells -> virus goes to DRG
  • VZV-specific immunity -> viral replication stops
  • virus reactivates when host cell-mediated immunity falls
• Sx: lesions evolve thru stages; successive crops TIMELINE
  
  • 1. macular
  • 2. papular
  • 3. vesicular: fluid collects in cell interspaces -> dewdrop rose petal -> highly infectious
  • scab
  • complications:
    
    • 7 to 10% mortality in leukemia Pt
    • fetal abnormalities & mortaility (infection of baby 5 d or less before delivery)
  • NOTE:
    
    • Rubeola and rubella rash starts on the face
    • Chicken pox rasg starts in the trunk and can spread to extremities
• Dx:
  
  • clinical dx most important
• Control: prevention
  
  • live vaccine for both children & adults & older already infected to prevent Shingles
  • Hyperimmune Ig (VZIG) available for immunocompromised accidentally exposed

Question 12

HPV

Answer 12

• Papovaviridae
• only specific types cause cancer in humans
• cause warts in various body sites (tissue tropism)
  
  • flat warts (verruca plana)
  • genital warts
  • plantar warts

Question 13

Family: Poxviridae

Answer 13

• replicates in cytoplasm
• family includes
  
  • small pox
  • monkey pox: zoonotic infection; 16% mortality; prarier dogs & monkeys
  • Tanapox: infection of lower primates, Tana river in Africa, occasionally humans
    
    • sx: 3-4 febrile perioid w body ahces, lsions develop slowly and become large -> heals in 2 - 7 wk
  • parapox: ORF (natural infection of sheep and goats)
    
    • Transmission: thru skin abrasions
    • sx: lesions develop from maculopapular rash that become elevated and eventually nodular -> lesion develops crush and heals after > 35 d

Question 14

Molluscum contagiosum

Answer 14

• ds DNA virus thought to belong to pox virus group.
• Disease: benigntumour of skin; usually 1 to 20 lesions lasting up to 2 years w 2nd cropy occassionaly lasting longer
• Transmission: predisposing factors
  
  • children get disease during play or sports
  • crowded living conditions
  • poor hygiene
  • sexual spread
• Etiopath:
  
  • opportunistic infection in AIDS Pt
• Sx: water wart -> tumour-like lesion
  
  • umbilicated papules 2 to 8 mm in diameter
  • molluscum body: white crater