Reply to Kjartansdóttir et al.: Chlorovirus ATCV-1 findings not explained by contamination.

We agree with Kjartansdóttir et al. (1) that extreme caution must be used when interpreting high-throughput sequencing results in new hosts. The situation demands thorough investigation and validation beyond the identification of a few sequencing reads. However, we believe it is unlikely that random laboratory contamination explains the results reported in Yolken et al. (2) for the following reasons. First, the presence of Acanthocystis turfacea chlorella virus 1 (ATCV-1) -like DNA sequences in the throat swab samples was confirmed by two methods, sequencing and PCR, and the experiments were performed in different laboratory areas using different procedures. Negative controls and controls containing DNA from other chloroviruses were routinely negative in the PCR reactions, making contamination by laboratory reagents unlikely. Furthermore, procedures used in the human studies involved extraction and amplification of DNA, and …