B19 usually causes a very mild disease. Two groups of people for whom it can be serious, however, are?: (A) teenagers and pregnant women, (B) pregnant women and sickle-cell anemics, (C) the sexually promiscuous and drug addicts, (D) alcoholics and asplenics
Answer is B. Primary infection in pregnant women is very serious and can result in death of the fetus. In patients with sickle-cell disease, the virus can initiate a transient aplastic crisis. Reference: Ananthanarayan and Paniker&;s Textbook of Microbiology Tenth edition