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  • STRUCTURE: Single-stranded DNA. The smallest of the DNA viruses.

  • REPLICATION: Occurs in nucleus. First, a complementary DNA (cDNA) is formed, which is then used as a template to form progeny virions.

  • Three Subtypes:

    • Densovirus: Infects insects.

    • Parvo Virus: Infects humans and animals, but there is no cross-infection.

    • Dependovirus: Depends on other viruses to replicate.

  • HUMAN PARVOVIRUS B19 (HPV B19): A parvovirus.

    • STRUCTURE: There is only one antigenic type, and immunity is lifelong and protective.


      • It requires dividing cells to divide. It likes erythroid precursor cells.

    • TRANSMISSION: Respiratory, or by blood transfusion.

    • DIAGNOSIS: Immune electron microscopy. ELISA or RIA. PCR.

      • Can assay serum IgM to detect acute infection.


      • Erythema Infectiosum: "Fifth Disease" in children.

        • Rash produces a "slapped-cheek" appearance on face, then proceeds to trunk and limb. This progression is like measles -- rash goes from the head down.

        • In adults, it produces mild fever, arthralgia, and limited rash.

      • Aplastic Crisis in people with Sickle Cell Anemia. Virus replicates in erythroid precursor cells and thus can result in fall in hemoglobin and aplastic crisis.

      • Hydrops Fetalis, Spontaneous Abortion: Hydrops fetalis occurs as a result of infection of fetal heart, liver, kidney, and RBC's, with consequent fall in hemoglobin.

      • Mild systemic and respiratory illnesses

  • ADENO-ASSOCIATED VIRUS (AAV): A Dependovirus. Defective virus requires Adeno or Herpes virus coinfection.


      • It produces a latent infection.

      • It integrates into host on specific site of chrom #9 as a provirus, so it is a good candidate for gene therapy.

    • MANIFESTATIONS: We don't know what disease, if any, this virus is associated with.

  • RA-1: Virus associated with Rheumatoid Arthritis.

Category: Microbiology Notes



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