The third sample was a UCHG duplicate swab in which the DNA may have been degraded.
Our estimate of the duration of the infectious period (8.3 d, 95% CI: [5.8, 14.3]) is consistent with measures of viral shedding, obtained by Peiris et al. [31] using quantitative reverse transcriptase on sequential nasopharyngeal aspirates/throat and nose swabs (NPA/TNS), in which maximum virus excretion occurs around the tenth day of illness (compare also [24]).
A sole detection episode was defined as ≥1 consecutive swab specimens in which an individual PyV was the only virus detected, and no other viruses were reported 7 days before or after detection of the PyV.
Specimen collection method may also have affected prevalence estimates: all studies among FSWs that reported chlamydia, gonorrhoea and trichomonas used self-collected vaginal swabs, in contrast to community and clinic-based studies in which swabs were collected by a trained clinician.
Swabs were collected by research assistants except for two studies, in which swabs were taken by the HCWs themselves [ 34, 54].
They include (from last year) a woman who had her fallopian tube removed instead of her appendix and 123 cases in which swabs, instruments or other items were left inside patients after surgery.
A recent study in which swabs were used to take cultures from the splash basin found a contamination rate of only 2% (Glait et al. 2011), and the authors speculated that the discrepancy might be partly due to differences in sampling methods but our findings do not support this.
(See Acknowledgements for full details) During both studies, monthly point prevalence surveys were performed, in which rectal swabs and throat swabs or endotracheal aspirates (respiratory samples) were obtained from all patients present in the ICU on the day of the survey.
Contrary to earlier findings (8 ) in which oropharyngeal swabs were more sensitive than cloacal swabs by using the VecTest antigen-capture assay, we found no appreciable difference in our study between the CT values of the cloacal and nasopharyngeal swab samples.
