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Viral Exanthems

Parvovirus B 19

Causes: "fifth disease", aplastic crises in patients with chronic anemias erythroblastosis fetalis, arthritis

Target organ: bone marrow erythroid precursors

High-level viremia occurs about 1 week after inoculation, Fever, malaise and myalgias last several days. Respiratory shedding of virus.

Shortly after infection, specific IgM and IgG response occurs

Fall in hemoglobin

About 10 days later: maculopapular rash, arthralgias, no viral shedding; immune complex disease

Common self-limited illness in children aged 5-14 years

Sudden onset of red cheeks, fever, maculopapular rash (for weeks); rate of secondary spread is about 30%

Asymptomatic infection common

About 60% of adults are antibody positive

Parvovirus B 19: Aplastic Crises viral exanthems, measles, mumps, rubella, chicken pox

Patients with sickle cell disease, spherocytosis, thalassemia may develop aplastic crises

Immunocompromised children: prolonged infections

Spread by respiratory droplets; nosocomial transmission occurs

Isolate children with chronic anemia and febrile aplastic crisis

Don't isolate children with fifth disease

Rubella: Postnatal

Symptoms: mild rash, fever, lymphadenopathy

Asymptomatic infection common (cannot use history for immunity)

Hemorrhagic complications in children: (low platelets vascular damage)

Symptoms are more pronounced in adults, arthralgia, arthritis (in females)

fingers, wrists, knees

Disease not more severe in immunocompromised

Rubella: Congenital

 Timing

1st, early 2nd trimester

1- 2 months: 50% with fetal abnormalities

4th month: 10% with single fetal abnormality

Spectrum

Cataract, congenital heart disease (PDA, PS), glaucoma, deafness, thrombocytopenia, diabetes

Fetal infection from maternal viremia

Pathogenesis unclear; mitotic arrest?

Rubella: Epidemiology

Less contagious than measles

Post-vaccine era: mini epidemics occur among susceptibles

Transmission: respiratory droplets; babies shed virus for many months despite antibodies

 Immunity imperfect

Reinfection without viremia common especially after vaccination

Nevertheless highly successful vaccine

Rubella: Diagnosis

Culture virus: expensive limited availability

Acute/convalescent antibody titers

Falling titer indicates that congenital infection is unlikely

 IgM can occur in reinfection

To diagnose congenital infection: match exam to lab results notify CDC; PCR

Mumps

Systemic infection with viremia, viruria