key: cord-0049936-wbo7nkq9 authors: Kotlyar, Alexander; Tal, Reshef title: Reply to SARS-CoV-2 Vertical Transmission and RNA Stability date: 2020-09-10 journal: Am J Obstet Gynecol DOI: 10.1016/j.ajog.2020.09.004 sha: e07a130610e6bbe8246d4ed77c78425f509b08c2 doc_id: 49936 cord_uid: wbo7nkq9 nan Title: Reply to SARS-CoV-2 Vertical Transmission and RNA Stability 1 2 Alexander Kotlyar MD 1 , Reshef Tal MD PhD 1 3 4 1 Section of Reproductive Endocrinology and Infertility, Department of Obstetrics, Gynecology, 5 and Reproductive Sciences, Yale School of Medicine, Yale University, New Haven, 6 Connecticut. 7 8 Disclosure statement: The author(s) report(s) no conflicts of interest. 9 10 11 No financial sources of support were used to compose this article. 12 13 Corresponding author: 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 J o u r n a l P r e -p r o o f We wish to thank Pomar and colleagues for their interest in our article and the important point 46 they raise in their letter. We acknowledge that RNA degrades more easily than DNA, and that 47 sampling, purification processes, storage and transport conditions can all influence RNA 48 stability, which may impact the ability to detect this RNA virus in placenta and certain fetal 49 samples using molecular assays. However, this appears to be much less of a concern when 50 assessing the presence of SARS-CoV-2 RNA in neonatal nasopharyngeal (NP) specimens. 51 Indeed, while our systematic review summarized the evidence of SARS-CoV-2 viral detection in 52 various fetal and neonatal clinical sites, the vertical transmission rate estimate of 3.2% of 53 COVID-19 infections occurring in the third trimester is based on our meta-analysis which was 54 focused specifically on neonatal NP swab testing, the gold standard to detect SARS-CoV-2 viral 55 RNA, performed within 48h of birth (1) . 56 Established methods of viral NP specimen collection and transport appear to preserve 57 discernible amounts of SARS-CoV-2 for an extended period. This exact question was recently 58 addressed by Rogers et al. (2) . In this prospective study, the authors assessed the effects of 59 various media, temperatures, and storage times on the stability of SARS-CoV-2 RNA specimens 60 obtained by NP swabs. Samples were defined as 'positive' if their PCR amplification cycle 61 number (C t ) was <40 and 'stable' if their mean C t value did not increase by more than three 62 amplification cycles of the initial Ct value. Importantly, all samples stored at room temperature 63 over seven days exhibited increasing Ct values over time but had C t value variation <3, thus not 64 impacting the qualitative interpretation of positive results. Such stability was maintained for all 65 five media types tested. Similar stability levels were seen in refrigerated and frozen samples even 66 after 14 days of storage in five different media (2). Notably, RNA stability was assessed in this 67 study for a much longer duration than is customary for routine clinical testing, further reducing 68 the likelihood of clinical impact. These stability assessments complement prior studies 69 evaluating the strong survival and persistence of the closely related SARS-CoV-1 in various 70 different human specimens and environments, as it was shown to survive in serum and feces at 71 infectious levels for at least 96h and in urine for at least 72h (3). 72 The goal of our meta-analysis was to summarize existing data and arrive at preliminary 73 estimates for the likelihood of vertical transmission of SARS-CoV-2, rather than exact viral 74 transmission rates. While we agree with the letter authors that viral RNA stability within 75 placental/fetal specimens may lead to underestimation of viral detection by qRT-PCR, the case 76 for vertical transmission is all the more strengthened with the relative consistency of SARS-77 CoV-2 detection rates in all of the clinical specimen sources reported in our systematic review. Transmission of COVID-19: A Systematic Review and Mates-Analysis Evaluation of Transport Media and Specimen Transport Conditions for the Detection of SARS-95 CoV-2 by Use of Real-Time Reverse Transcription-PCR Stability of SARS Coronavirus in 97 human specimens and environment and its sensivity to heating and UV irradiation