1. History

• 1975 - human parvovirus B19 (single-stranded DNA) first discovered
• 1981 - B19 parvovirus not associated with a disease until 1981 when found to be associated with an aplastic crisis in a patient with sickle cell anemia
• 1983 - B19 parvovirus associated Fifth Disease
• 1984 - found to be a source of intrauterine infection
• 1985 - associated with some forms of acute arthritis

2. Background

• parvovirus B19 tends to replicate in erythroid progeniter cells inhibiting erythropoiesis leading to a transient anemia
• in healthy individuals, parvovirus B19 infection usually causes a transient RBC aplasia that is asymptomatic
• parvovirus B19 may also cause an asymptomatic infection, a mild respiratory illness, an atypical rash, arthritis, chronic anemia (in immunodeficient patients), and an aplastic crisis (in patients with chronic hemolytic anemias)
• incubation period between 4-21 days (period of time from the acquisition of infection to onset of the initial symptoms)
• persons are most infectious during the incubation period and are unlikely to be infectious after the onset of the rash

3. Route of Transmission

• humans are the only known host for parvovirus B19 and the virus is transmitted by human-to-human contact via respiratory secretions or by blood (and blood products)
• infections occur sporadically or as community outbreaks (usually in elementary or junior high schools in the spring)
• parvovirus B19 infection is most common in school age children and greater than 50% of adults have serologic evidence of past infection:
  • 10% of cases found in those less than 5 years of age
  • 70% of cases found in those between 5-15 years of age
  • 20% of cases found in those greater than 15 years of age
• the secondary attack rate in susceptible household members is about 50%
• persons at risk: teachers, day-care workers, paediatric health-care providers
• there is a 9-10% risk of fetal hydrops or death if infection is acquired by a seronegative mother within the first 20 weeks of pregnancy; the incidence of fetal hydrops or death is less than 10% if an in utero infection is acquired in the second half of pregnancy (see Congenital Parvovirus B19)

1. Prodrome

• preceds the rash by 7-10 days
• mild respiratory tract symptoms
  • headache
  • low grade fever
  • malaise
  • myalgia
  • pharyngitis

2. Skin Manifestations