WBR0064

Author	PageAuthor::William J Gibson (Reviewed by Yazan Daaboul)
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Microbiology
Sub Category	SubCategory::General Principles, SubCategory::Infectious Disease
Prompt	[[Prompt::A 3-year-old boy is brought to the pediatrician's office after his mother noticed that he has had several episodes of watery diarrhea for the past 2 days. The mother reports that several of her son's playmates from daycare have had similar symptoms as well. Which of the following best describes the most likely infectious agent of this patient's condition?]]
Answer A	AnswerA::ssDNA virus
Answer A Explanation	[[AnswerAExp::The parvovirus family is composed of ssDNA viruses. Parvovirus B19 is responsible for erythema infectiosum in children (also known as fifth disease or slapped cheek syndrome).]]
Answer B	AnswerB::dsDNA virus
Answer B Explanation	AnswerBExp::The majority of DNA viruses are composed of dsDNA, such as herpesvirus, adenovirus, papillomavirus, polyomavirus, and poxvirus. Hepadnavirus is also a DNA virus, but it is only partially double-stranded.
Answer C	AnswerC::ssRNA virus
Answer C Explanation	AnswerCExp::Most RNA viruses, including the Norwalk virus are composed of ssRNA. While the Norwalk virus is a cause of diarrhea in both children and adults, it is not the most common cause of watery diarrhea in children.
Answer D	AnswerD::dsRNA virus
Answer D Explanation	AnswerDExp::Rotavirus is the leading cause of watery diarrhea in children. It is a non-enveloped segmented dsRNA reovirus with an icosahedral capsid.
Answer E	AnswerE::Bacteria
Answer E Explanation	AnswerEExp::Bacteria are not the most common cause of watery diarrhea in children.
Right Answer	RightAnswer::D
Explanation	[[Explanation::Rotavirus, an non-enveloped segmented dsRNA reovirus with an icosahedral capsid, is the most common cause of watery diarrhea in children. It is particularly prevalent in settings where many children come in contact with each other, such as daycare centers. Rotavirus causes watery diarrhea because the virus causes sloughing off of intestinal mucosa that leads to poor absorption of water and Na+. The infection typically lasts a few days before spontaneous recovery. However, some cases require hospitalization for rehydration following dehydration associated with severe diarrhea. Residual lactose intolerance as a result of epithelial degeneration may require prolonged periods of time before recovery. Educational Objective: Rotavirus is the most common cause of watery diarrhea in children. It is is a dsRNA virus. References: First Aid 2014 page 162]]
Approved	Approved::Yes
Keyword	WBRKeyword::Microbiology, WBRKeyword::watery, WBRKeyword::Diarrhea, WBRKeyword::Gastrointestinal, WBRKeyword::Virus, WBRKeyword::Viruses, WBRKeyword::RNA virus, WBRKeyword::rotavirus, WBRKeyword::reovirus, WBRKeyword::classification, WBRKeyword::RNA
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