Parvovirus B19

Late winter and spring outbreaks are most common
Most common in school aged children
1. Parvovirus Antibody present in >50% over age 15 years
Incidence of Arthritis
1. Children: 5% to 10% develop short-term mild Arthritis
2. Adults: 78% develop significant joint symptoms

Parvovirus (Parvoviridae)
1. Parvovirus is a family of tiny DNA Viruses that infect Vertebrates and invertebrates
2. Nonenveloped (naked), Linear, single-stranded DNA Virus (negative ssDNA) with icosahedral capsid
Human Parvovirus (B19)
1. Known as Fifth Disease for its being the fifth named Childhood Exanthem (after Measles, Scarlet Fever, Rubella, coxsackievirus)
2. Inactivated by heat,detergents (No lipid envelope)
3. Targets P Antigen receptor on erythroid progenitors
  1. Bone Marrow
  2. Fetal liver and Umbilical Cord
  3. Peripheral blood
Transmission modes
1. Exposure to infected respiratory droplets or blood
2. Vertical transmission from mother to fetus
Transmission rates
1. Living with infected person: 50%
2. Teacher, daycare worker of infected children: 20-30%
Transmission timing
1. Not contagious after rash onset
2. May Return to School once rash appears

Children are often asymptomatic
Prodromal symptoms (precede rash by 2 weeks)
1. Low grade fever
2. Nausea or gastrointestinal upset
3. Coryza
4. Headache
5. Pharyngitis
Subsequent symptoms
1. Pruritic exanthem in children (see below)
2. Myalgia and Arthralgia (see below)

Child is no longer contagious after the rash appears
Stage 1: Slapped Cheek (onset within 2 weeks of prodromal symptoms)
1. Cheek erythema ("Slapped Cheek") appearance on face
2. Circumoral pallor
3. Facial erythema spares the chin, perioral region, Nasal Bridge and periorbital region
Stage 2: Trunk and Extremity Rash (follows facial rash by 1-4 days)
1. Lacy-reticular pink maculopapular (blotchy) rash
  1. Macular central clearing results in the lacy-reticular pattern
2. Involves trunk and extremities for 1-3 weeks (esp. extensor surfaces)
3. Rash is pruritic (50% of cases)
Stage 3: Rash Recrudescence (recurrence after stage 2 rash fades)
1. Rash recurrs over the next 3 weeks when triggered by provocative factors
2. Provocative factors
  1. Sunlight exposure
  2. Heat
  3. Exercise

Incidence in Parvovirus Infection
1. Children: 8%
2. Adolescents and Young Adults: 60% (twice as likely in women than men)
Rheumatoid-like joint involvement
1. Hand involvement (most common in adults, bilateral)
  1. Metacarpophalangeal joints (MCP joints)
  2. Proximal interphalangeal joints (PIP joints)
2. Wrist involvement
3. Leg Involvement (most common in children)
  1. Knee involvement (82% of children)
  2. Ankle Joint involvement
Arthralgia and Arthritis course
1. Onset 1-3 weeks following initial infection
2. Improves in most patients by 2 weeks
3. Treated with NSAIDs for analgesia
4. Self limited course in 90% of patients
5. Prolonged Arthritis in 10% may last up to 10 years
6. Morning stiffness
Associated conditions
1. Rheumatoid Arthritis
2. Systemic Lupus Erythematosus

Anti-B19 IgM Antibody
1. Test Sensitivity: 89%
2. Test Specificity: 99%
3. Elevated for 2-3 months after acute infection
Parvovirus DNA by PCR testing
1. Similar sensitivity to IgM testing
2. Indicated in aplastic crisis or if Immunocompromised
3. Persistence suggests chronic Parvovirus Infection
Peripheral Blood Smear or Bone Marrow findings
1. Giant pronormoblasts
2. Non-specific finding
Variably present serologies at low to moderate titer
1. Rheumatoid Factor (RF)
2. Antinuclear Antibody (ANA)
3. Anti-dsDNA
4. Anti-ssDNA
5. Anti-cardiolipin Antibody

Pregnant women should avoid contact with Parvovirus
1. Risk of transmission to fetus: 30%
2. Risk of Hydrops fetalis with findings in newborn:
  1. Severe Anemia
  2. High output cardiac failure
  3. Extramedullary hematopoiesis
3. Risk of fetal loss (2-6%)
4. Risk of congenital infection syndrome
  1. Rash
  2. Anemia
  3. Hepatomegaly
  4. Cardiomegaly
5. Risk per timing of exposure in pregnancy
  1. Highest risk: Second trimester
  2. Lowest risk: First trimester
Child with Erythema Infectiosum does not need isolation
1. May attend school and daycare once rash appears
2. Hospital isolation is not needed
Evaluation and mangement post-exposure in pregnancy
1. Labs to confirm maternal Parvovirus Infection
  1. Parvovirus B19 IgM or
  2. Parvovirus B19 IgG seroconversion
2. Monitoring pregnancy if testing positive
  1. Serial Ultrasounds weekly for 10-12 weeks
  2. Fetal hydrops present by Ultrasound
    1. Fetal blood sampling
    2. Fetal transfusion as needed

See Transient Red Cell Aplasia
General
1. May be life threatening
2. Monitor closely for possible transfusion
Transient aplastic crisis in chronic Anemia
Chronic Bone Marrow suppression in Immunocompromised
1. Malignancy
2. Transplant recipient
3. Human Immunodeficiency Virus
Course
1. Typical full recovery within 2 weeks