This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Rotavirus infection is diagnosed by the presence of? 
Select and explain. 
A. Antigen in stool by ELISA, B. Virus in stool, C. Antigen in blood, D. Antibody in stool
A: Antigen in stool by ELISA
Answer: A: Antigen in stool by ELISA 
Explanation: Ans. is 'a' i.e., Antigen is stool by ELISA Because Rotavirus is shed in large amounts is stool, detection is relatively easy. Most commonly used are commercial immunoassays to detect rotavirus antigen in fecal specimen.