Dr. Marwa A. Meheissen: Parvoviruses & Adenoviruses ILOs Quiz

Parvoviruses

• Parvoviruses are the smallest DNA viruses, naked, and icosahedral with a single-stranded DNA genome.
• They have a limited coding capacity, so they depend on functions supplied by replicating host cells.
• Viral DNA replication occurs in the nucleus and requires one or more cellular DNA polymerases.
• Parvoviruses cannot stimulate resting cells to initiate DNA synthesis, so they must infect dividing cells.

Infections Caused by Parvoviruses

• Parvovirus B19 is pathogenic for humans and has a tropism for erythroid progenitor cells.
• Human bocavirus is believed to cause wheezing and respiratory infections in children.
• B19 virus is widespread and can cause infections throughout the year in all age groups, as outbreaks or sporadic cases.

Pathogenesis of Parvovirus Infections

• Immature cells in the erythroid lineage are the principal targets for human B19 parvovirus.
• The major sites of virus replication are the adult marrow, some blood cells, and the fetal liver.
• The incubation period is usually 1–2 weeks but may extend to 3 weeks.
• Viremia occurs 1 week after infection and persists for about 5 days.
• The first phase of illness occurs at the end of the first week, with symptoms like flu, fever, malaise, myalgia, chills, and itching.
• The first episode of illness coincides with viremia and reticulocytopenia and detection of circulating IgM–parvovirus immune complexes.
• A second phase of illness begins after an incubation period of about 2 weeks, with an erythematous facial rash (“slapped cheek” appearance) and a lace-like rash on the limbs or trunk.

Immunity and Diagnosis

• Specific IgG antibodies appear about 15 days post-infection.
• Detection of B19 IgM antibody indicates recent infection, which is present for 2–3 months after infection.
• B19 IgG antibody persists for years.
• Antibody may not be found in immunodeficient patients with chronic B19 infections.
• In those patients, chronic infection is diagnosed by detecting viral DNA.
• Antigen detection assays can identify B19 virus in clinical samples.

Treatment and Prevention

• There is no antiviral drug therapy.
• Fifth disease and transient aplastic crisis are treated symptomatically.
• Severe anemia may require transfusion therapy.
• Commercial immunoglobulin preparations contain neutralizing antibodies to human parvovirus.
• Good hygienic practices, such as hand washing and not sharing drinks, can help prevent the spread of B19.
• Contact precautions and extensive patient room cleaning may help prevent transmission of B19 from patients with aplastic crisis and from immunodeficient patients with chronic B19 infection.

Adenoviruses

• Adenoviruses are naked, icosahedral, and double-stranded DNA viruses.
• The overall risk of human parvovirus infection during pregnancy is low, with fetal loss occurring in fewer than 10% of primary maternal infections.
• Fetal death occurs most commonly before the 20th week of pregnancy.

Human Bocavirus Respiratory and Gastrointestinal Infections

• Human bocavirus has been detected in 1.5–11.3% of respiratory tract samples from young children with respiratory infections.
• It is prevalent among children with acute wheezing.
• The virus has been detected in about 3% of stool samples from children with acute gastroenteritis.
• Coinfection rates with other enteric pathogens are also high, so any causative role of bocavirus in gastroenteritis remains uncertain.

Diagnosis of Adenovirus Infections

• Detection of nucleic acid is the most sensitive test, with PCR being the most sensitive assay.
• Adenovirus DNA has been detected in serum, blood cells, tissue samples, and respiratory secretions.

Clinical Manifestations of Adenovirus Infections

• About one-third of the known human serotypes are commonly associated with human illness.
• Adenoviruses 1–7 are the most common types worldwide and account for most instances of adenovirus-associated illness.
• Adenoviruses are responsible for about 5% of acute respiratory disease in young children, but they account for much less in adults.
• Typical symptoms of adenovirus infections include cough, nasal congestion, fever, and sore throat.
• Adenoviruses are thought to be responsible for about 10–20% of pneumonias in childhood.
• Adenoviruses are the cause of an acute respiratory disease syndrome among military recruits.

Test your knowledge on Parvoviruses and Adenoviruses with this quiz based on the lecture by Dr. Marwa A. Meheissen. Explore general characteristics, infections, laboratory results, and pathogenesis of these viruses.