Table 1.
Detection of SARS-CoV-2 in wastewater, residents and staff at nursing homes included in the study
| Nursing home (no. of residents/no. of staff) | Surveillance period | Date of first detection of SARS-CoV-2 RNA in wastewatera/day at which peak RNA levels (log10 GC/L) was reached | Date of first reported case of SARS-CoV-2 infection at the nursing home | No. of residents testing positive for SARS-CoV-2b,c | No. of staff testing positive for SARS-CoV-2b,c | Last SARS-CoV-2 infection case documented among residents or staff | Previous outbreaks |
|---|---|---|---|---|---|---|---|
| A (103/58) | 14 October to 28 December | 21 October/29 October (4.5) | 9 November | 1d | — | 9 November | Yes (16 June) |
| A (103/58) | 14 October to 28 December | 10 December/28 December (8.6) | 17 December | 25 | 13 | Outbreak ongoing | Yes (16 June and 21 October) |
| B (105/60) | 6 November to 28 December | 6 November/19 November (4.5) | 11 November | — | 1e | 11 November | Yes (17 June and 5 October) |
| C (48/25) | 6 November to 28 December | ND | NR | — | — | — | No |
| D (101/81) | 7 October to 28 December | 7 October/12 November (6.9) | NRf | — | — | — | Yes (9 July) |
| E (115/85) | 7 October to 28 December | 26 October/30 October (8.3)g | 17 October | 14 | 10 | 16 November | Yes (17 June and 13 July) |
ND, not detected; NR, not reported.
RNA extraction from sewage material was carried out using the NucleoSpin RNA virus Kit (Macherey-Nagel, Düren, Germany). SARS-CoV-2 RNA detection was performed by RT-qPCR using One-Step PrimeScript™ RT-PCR Kit (Perfect Real Time) (Takara Bio, Mountain View, CA, USA), targeting the nucleoprotein (N), N1 and N2 fragments, and envelope protein (E) gene [4,5]. RNA samples were analysed in duplicate. Each RT-qPCR run included negative (nuclease-free water) and positive controls. RT-qPCR targets were quantified by plotting the quantification cycles (CT) to an external standard curve built with ten-fold serial dilution of the 2019-nCoV_N_Positive Control and 2019-nCoV_E_Positive Control (IDT). Mengovirus RNA recovery rates were calculated and used as quality assurance parameters according to ISO 15216-1:2017.
Nasopharyngeal swabs (NP) for RT-PCR testing were collected by experienced nurses at the Nursing Home sites and immediately placed in 3 mL of Universal Transport Medium (UTM, Becton Dickinson, Sparks, MD, USA). RT-qPCRs were conducted within 24 h of specimen collection at the Microbiology Service of Hospital Clínico Universitario (Valencia, Spain) with the TaqPath COVID-19 Combo Kit (Thermo Fisher Scientific, Waltham, MA, USA). RNA was extracted using the Applied Biosystems MagMAX™ Viral/Pathogen II Nucleic Acid Isolation Kits coupled with KingFisher Flex automated instrument (Thermo Fisher Scientific).
No reinfections were documented among residents and staff.
Resident tested for SARS-CoV-2 infection because appearance of symptoms compatible with COVID-19 (fever and cough).
Staff (asymptomatic) tested as a close household contact of a COVID-19 case.
Residents and Staff members were screened for SARS-CoV-2 infection by RT-PCR on 29 October.
Two of the four sewage draining sites were not tested until 26 October.