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Parvovirus B19 Infection

BASICS

  • Definition: Human parvovirus B19 causes erythema infectiosum ("fifth disease").
  • Key Complications:
  • Increased RBC turnover (sickle cell, spherocytosis, thalassemia): transient aplastic crisis (TAC)
  • Immunocompromised: pure red cell aplasia, transfusion-dependent anemia
  • Immunocompetent: arthritis and arthralgias are common

EPIDEMIOLOGY

  • Peak Age: 4–12 years; common in childhood, often asymptomatic
  • Arthritis: More common in women (post-infectious)
  • Outbreaks: Late winter–early summer; epidemics every 2–5 years
  • Seroprevalence: By age 5, 2–15% IgG+; >70% by age 40
  • Pregnancy: 30–40% of women are seronegative (susceptible)

ETIOLOGY & PATHOPHYSIOLOGY

  • Agent: Small, nonenveloped ssDNA virus (Erythrovirus genus)
  • Spread: Respiratory droplets (main); most contagious 5–10 days after exposure (before rash)
  • Incubation: 4–14 days
  • Rash:
  • Stage 1: "Slapped cheek" appearance
  • Stage 2: Lacy, reticulated, erythematous macular rash (trunk/extremities, spares palms/soles)
  • Duration: Rash/joint symptoms resolve within 3 weeks
  • Cytotoxicity: Infection of erythroid progenitor cells → decreased RBC production → TAC in susceptible hosts
  • Genetics: Individuals lacking erythrocyte P antigen are resistant

RISK FACTORS

  • Close contact with infected children (school, daycare)
  • Conditions with increased RBC turnover (sickle cell, thalassemia, spherocytosis)
  • Immunodeficiency (congenital, HIV, malignancy)
  • Pregnant women (seronegative, exposed)

PREVENTION

  • No vaccine available
  • Hand washing, cough/sneeze hygiene, droplet precautions for TAC or immunocompromised
  • No exclusion from work needed if precautions followed

ASSOCIATED CONDITIONS

  • Arthritis:
  • Children: uncommon, knees/ankles
  • Adults: common, symmetric, hands > larger joints; often resolves in weeks but can persist (women > men)
  • Transient Aplastic Crisis (TAC): Severe anemia, reticulocytopenia in high RBC turnover conditions; fever common, rash rare in these patients
  • Chronic anemia: Immunocompromised (HIV, cancer); may need transfusion
  • Pregnancy/fetal:
  • ~30% vertical transmission
  • Fetal death 5–10%; highest risk in 1st trimester (up to 19%)
  • Fetal hydrops, anemia, heart failure possible
  • Gloves and socks syndrome: Painful/pruritic papules, purpura, vesicles on hands/feet, usually resolves in 1–3 weeks

DIAGNOSIS

History

  • Prodrome: fever, malaise, headache, myalgia, coryza
  • Rash/arthralgias develop after prodrome

Physical Exam

  • "Slapped cheek" rash, spares nasolabial folds
  • Lacy, reticulated rash on trunk/limbs (pruritic, can recur with heat/exercise)
  • Painful/pruritic papules, purpura, glove and sock distribution (adults)

Differential

  • Rubella, measles, enteroviral disease, SLE, drug reaction, rheumatoid arthritis

Diagnostics

  • Clinical diagnosis in typical cases (no labs needed)
  • Serology (IgG, IgM): in pregnancy, immunodeficiency, chronic/refractory anemia, fetal infection
  • PCR for B19 DNA: fetal diagnosis (amniotic fluid, cord blood); immunocompromised
  • TAC: anemia with reticulocytopenia
  • Pregnancy exposure: serial serology, fetal US for hydrops, Doppler for MCA velocity

TREATMENT

General

  • No specific therapy required for most
  • Supportive: anti-inflammatories for joint symptoms, antipyretics for fever

Medications

  • First line: Symptomatic care (analgesics, antipyretics)
  • Second line:
  • RBC transfusion for TAC
  • IVIG for severe/chronic anemia (immunodeficient)
  • Intrauterine transfusion for fetal hydrops
  • Immunosuppressed: Consider reduction of immunosuppressive therapy if possible

Referral

  • Acute infection in pregnancy: refer to maternal-fetal medicine
  • Chronic/parvovirus-related anemia: immunology/infectious disease

ADMISSION, INPATIENT, NURSING

  • Outpatient: Erythema infectiosum, most immunocompetent
  • Inpatient: TAC requiring transfusion, severe anemia, chronic anemia (immunodeficient), fetal monitoring
  • Droplet isolation for acute/chronic, TAC in immunocompromised

FOLLOW-UP

  • Monitor: Anemic patients—periodic blood counts until reticulocyte recovery
  • Pregnant women: Fetal US/Doppler if exposed/infected

PATIENT EDUCATION

PROGNOSIS

  • Usually self-limited
  • Joint symptoms usually resolve within 3 weeks (may persist in some)
  • TAC: full recovery in 2–3 weeks
  • Fetal death: 5–10% if infected in utero

COMPLICATIONS

  • Severe/fatal anemia (TAC), hydrops fetalis, fetal death
  • Hepatitis, fulminant hepatic failure, myocarditis, pericarditis, glomerulonephritis, nephrotic syndrome, HSP, ITP, vasculitis, hemophagocytic syndrome (rare, causality unproven)

ICD-10 Codes

  • B34.3 Parvovirus infection, unspecified
  • B08.3 Erythema infectiosum [fifth disease]

CLINICAL PEARLS

  • Classic “slapped cheek” rash appears after peak infectivity—patients no longer contagious when rash appears
  • TAC risk: sickle cell, thalassemia, spherocytosis
  • Chronic anemia risk: immunodeficient patients
  • Pregnancy: acute infection requires specialist referral; fetal death risk highest in 1st trimester
  • No vaccine available