This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology, Subject name: Microbiology
Erythema infectiosum is caused by - 
Select and explain. 
A. Parvovirus B19, B. JC virus, C. Rotavirus, D. Mumps
A: Parvovirus B19
Answer: A: Parvovirus B19 
Explanation: Ans. is 'a' i.e., Parvovirus B-19 * Parvovirus are non-enveloped DNA (ss DNA) viruses.* Only DNA virus which has single stranded DNA.* Smallest virus* Has smallest genome* Only one medically important human parvovirus - Parvovirus B19* Transmission is by respiratory route and through blood.* Infection is commonly acquired in childhood (5-10 yrs).* Most of the infections are asymptomatic.* Most common presentation is respiratory infection with an erythematous maculopapular rash and arthralgia - Erythema infectiosum or Fifth disease.* Starts with prominant erythema of cheeks ->> slapped cheek disease.* Parvovirus B-19 induces aplastic crisis in children with chronic hemolytic anemias, as in sickle cell disease.* Parvovirus B-19 infection during second or third trimester of pregnancy may result in nonimmune fetal hydrops. Transplacental transmission rate is 30% or higher.* In adults, parvovirus infection commonly causes acute arthralgia and arthritis.* Parvovirus B-19 is difficult to grow and virus isolation is not used to detect infection.