Figure 2.

A, AstV-contig polymerase chain reaction results for all retrospectively tested samples from patient A. Data points at the base of the y-axis indicate astrovirus (HAstV)–VA1/HMO-C-UK1(a) RNA not detected. Cycle threshold (Ct) values represent the cycle number at which amplification was detected and thus have an inverse relationship with viral titer; a smaller Ct value indicates a higher titer. In clinical practice, Ct >38 may be considered equivocal but, in the context of other positive results, is considered a true positive. A difference of 3 Ct values is approximately equivalent to a 10-fold difference in viral load. B, Clinical and diagnostic timeline. Abbreviations: AstV, astrovirus; CSF, cerebrospinal fluid; HAstV, human astrovirus; NPA, nasopharyngeal aspirate.