<prompt> The virus which causes aplastic anemia in chronic hemolytic diseases is -AdenovirusHepatitis virusEB virusParvovirus  <response>: Ans. is d i.e., Parvo virus B-19 Parvovirus B-19 induces aplastic crisis in children with chronic hemolytic anemias, as in sickle cell disease. Parvovirus . Non-enveloped DNA ss DNA viruses. . Only DNA virus which has single stranded DNA. . Smallest virus . Has smallest genome . Only one medically impoant human parvovirus - Parvovirus B 19 . 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 ahralgia - Erythema infectiosum or Fifth disease. . Stas 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. 