A mother brings her 3 year old boy into the emergency room because he has developed a harsh, "barking"cough with hoarseness. The virus responsible for this child's following illness belongs to which of the families?

You probably realized that the child in question suffers from croup (laryngotracheobronchitis); the classic clue here is the "barking cough." You might have remembered that the virus responsible for croup is the parainfluenza virus. The toughest pa was remembering that parainfluenza virus (along with measles virus, mumps virus, and respiratory syncytial virus) belongs to the paramyxovirus family. These viruses all have negative-strand RNA and an enveloped helical nucleocapsid. The papovaviruses are DNA viruses with a naked icosahedral nucleocapsid. This family includes the human papilloma viruses (which cause was and are associated with penile, laryngeal, and especially, cervical cancer), the BK virus that can affect immunosuppressed patients, the JC virus associated with progressive multifocal leukoencephalopathy, and the simian SV40 virus. The parvoviruses are small, single-stranded DNA viruses. Only one serotype (B19) causes diseases in humans. It causes erythema infectiosum in children (characteristic "slapped cheek" rash), aplastic crises in patients with hemolytic diseases, and hydrops fetalis or stillbih in anemic fetuses. The picornaviruses are positive single-stranded RNA viruses with a naked icosahedral nucleocapsid. This family includes the polioviruses, echoviruses, coxsackieviruses, enterovirus 72 (Hep A virus), and the rhinoviruses (common cold). Ref: Levinson W. (2012). Chapter 31. Classification of Medically Impoant Viruses. In W. Levinson (Ed), Review of Medical Microbiology & Immunology, 12e.