Vol. 20, No. 18
THE JOHNS HOPKINS MICROBIOLOGY NEWSLETTER
Tuesday, May 1, 2001
 

1. Provided by Leslie Edwards Reger, Division of Outbreak Investigation, Maryland Department of Health and Mental Hygiene.

Case Report: The patient is a 16-month-old Caucasian male with a history of mild iron deficiency anemia who was brought to his pediatrician with a fever of 102°F and "pink-eye" which had been preceded by one day of mild diarrhea and coryza. His social history was significant for extensive exposure to young children and being the son of a pathology resident currently rotating on the microbiology service. On physical exam, the patient was febrile and slightly tachycardic but cheerful and in no acute distress. He had crusty yellow discharge from his right eye and his right sclera was slightly erythematous. His face was also notable for a classic "slapped-cheek" rash (see Figure 1). The remainder of his exam was unremarkable and the patient was diagnosed with erythema infectiosum based on clinical exam.

Organism: Parvovirus B19, is the only known human pathogen of the erythrovirus genus, a member of the Parovovirinae family. Parvoviridae are small, non-enveloped, single-stranded DNA viruses. Parvovirus B19 is dependent on mitotically active cells for replication and targets erythroid progenitor cells in the bone marrow. Infection is common in childhood and approximately 50% of children have detectable IgG to B19 by age 15. Infection also occurs in adults and 90% of elderly person have detectable IgG. Infection is most common in the late winter, spring, and early summer. B19 is transmitted by respiratory secretions and appears highly infectious with up to a 50% secondary attack rate in IgG negative close contacts of infected individuals. The virus can also be transmitted by blood and blood products but high titers of B19 are seen in only 1 in 20,000 to 40,000 donor units.

Clinical Manifestations: Erythema infectiousum or "fifth disease" usually manifests with a non-specific prodromal illness that may include fever, headache, coryza, nausea, or diarrhea. The classic slapped-cheek rash appears 2 to 5 days later followed by a second-stage rash a few days later. This second rash usually consists of a lacy, erythematous maculopapular exanthum over the trunk and limbs but may vary in intensity from barely perceptible to florid.

Arthropathy caused by B19 is more common in adults and usually consists of symmetric arthralgia and/or arthritis in the hands and feet. Symptoms usually last 1 to 3 weeks but can persist and recur for months or even years. Diagnostic confusion with rheumatoid arthritis is possible and B19 infection can be associated with a transient elevated rheumatoid factor.

Transient aplastic crisis (TAC) can occur in B19 infection in patients with underlying hemolytic disorders including sickle cell anemia, thalassemia, hereditary spherocytosis, and autoimmune hemolytic anemia, among others. TAC can also be seen in patients with "erythroid stress" such as iron deficiency anemia or hemorrhage. Patients with TAC can be severely ill with worsening anemia, dyspnea, congestive heart failure, bone marrow necrosis. Persistent B19 viremia seen in immunosuppressed patients can cause pure red blood cell aplasia.

Fetal B19 infection probably causes 10 to 15% of nonimmune hydrops, a rare birth defect (1 in 3000). Maternal B19 infection during pregnancy is associated with a slight increased risk of miscarriage (9% increased risk). ¹

Two case reports of conjunctivitis caused by parvovirus B19 have been published, one in a 10-year-old child and one in a 26-year-old woman.^,
 

Diagnosis: Parvovirus B19 infection can be detected by IgM assays (RIA, ELISA) which should be elevated in immunocompetent patients by the third day of TAC or as the time of rash presentation in erythema infectiousum. IgM antibody remains detectable for 2 to 3 months after infection. Viral DNA can be detected by PCR in serum, bone marrow, synovial fluid, and liver.¹ Parvovirus b19 can be grown in special erythroid cultures in vitro, but this is not routinely performed in the clinical laboratory.

Prevention and Treatment: Treatment is supportive in most cases. IVIG has been given in immunosuppressed patients with documented persistent B19 infection. Intrauterine blood transfusion for cases of hydrops fetalis in maternal B19 infection remains controversial but possibly effective. A vaccination for parvovirus B19 is in development. While patients with erythema infectiousum are viremic before their symptoms appear, isolation is not recommended in this manifestation. However, patients with TAC and pure red blood cell aplasia are both viremic and infectious and should be isolated from high-risk contacts.

References:
1.  Brown KE: Parvovirus B19, p. 1687-1693. In Mandel GL, Bennett JE, Dolin R (ed.), Principles and Practice of Infectious Diseases. 5th ed. Churchill Livingstone, Philadelphia, 2000.
2.  Scharre JE, Veith J: Conjunctivitis associated with fifth disease in a child: a case report. J Am Optom Assoc 67:763-6, 1996.
3.  Yoshida M, Tezuka T: Conjunctivitis caused by human parvovirus B19 infection. Opthalmologica 208:161-2, 1994.