Electrochemical sensing of SARS-CoV-2 amplicons with PCB electrodes

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused more than 200,000 reported COVID-19 cases in Spain resulting in more than 20,800 deaths as of April 21, 2020. Faecal shedding of SARS-CoV-2 RNA from COVID-19 patients has extensively been reported. Therefore, we investigated the occurrence of SARS-CoV-2 RNA in six wastewater treatments plants (WWTPs) serving the major municipalities within the Region of Murcia (Spain), the area with the lowest COVID-19 prevalence within Iberian Peninsula. Firstly, an aluminum hydroxide adsorption-precipitation concentration method was validated using a porcine coronavirus (Porcine Epidemic Diarrhea Virus, PEDV) and mengovirus (MgV). The procedure resulted in average recoveries of 10 ± 3.5% and 10 ± 2.1% in influent water (n = 2) and 3.3 ± 1.6% and 6.2 ± 1.0% in effluent water (n = 2) samples for PEDV and MgV, respectively. Then, the method was used to monitor the occurrence of SARS-CoV-2 from March 12 to April 14, 2020 in influent, secondary and tertiary effluent water samples. By using the real-time RT-PCR (RT-qPCR) Diagnostic Panel validated by US CDC that targets three regions of the virus nucleocapsid (N) gene, we estimated quantification of SARS-CoV-2 RNA titers in untreated wastewater waters of 5.4 ± 0.2 log10 genomic copies/L on average. Two secondary water samples resulted positive (2 out of 18) and all tertiary water samples tested as negative (0 out 12). This environmental surveillance data were compared to declared COVID-19 cases at municipality level, revealing that members of the community were shedding SARS-CoV-2 RNA in their stool even before the first cases were reported by local or national authorities in many of the cities where wastewaters have been sampled. The detection of SARS-CoV-2 in wastewater in early stages of the spread of COVID-19 highlights the relevance of this strategy as an early indicator of the infection within a specific population. At this point, this environmental surveillance could be implemented by municipalities right away as a tool, designed to help authorities to coordinate the exit strategy to gradually lift its coronavirus lockdown.

Summary Background There is little published evidence on the gastrointestinal features of COVID‐19. Aims To report on the gastrointestinal manifestations and pathological findings of patients with COVID‐19, and to discuss the possibility of faecal transmission. Methods We have reviewed gastrointestinal features of, and faecal test results in, COVID‐19 from case reports and retrospective clinical studies relating to the digestive system published since the outbreak. Results With an incidence of 3% (1/41)‐79% (159/201), gastrointestinal symptoms of COVID‐19 included anorexia 39.9% (55/138)‐50.2% (101/201), diarrhoea 2% (2/99)‐49.5% (146/295), vomiting 3.6% (5/138)‐66.7% (4/6), nausea 1% (1/99)‐29.4% (59/201), abdominal pain 2.2% (3/138)‐6.0% (12/201) and gastrointestinal bleeding 4% (2/52)‐13.7% (10/73). Diarrhoea was the most common gastrointestinal symptom in children and adults, with a mean duration of 4.1 ± 2.5 days, and was observed before and after diagnosis. Vomiting was more prominent in children. About 3.6% (5/138)‐15.9% (32/201) of adult and 6.5% (2/31)‐66.7% (4/6) of children patients presented vomiting. Adult and children patients can present with digestive symptoms in the absence of respiratory symptoms. The incidence of digestive manifestations was higher in the later than in the early stage of the epidemic, but no differences in digestive symptoms among different regions were found. Among the group of patients with a higher proportion of severe cases, the proportion of gastrointestinal symptoms in severe patients was higher than that in nonsevere patients (anorexia 66.7% vs 30.4%; abdominal pain 8.3% vs 0%); while in the group of patients with a lower severe rate, the proportion with gastrointestinal symptoms was similar in severe and nonsevere cases (nausea and vomiting 6.9% vs 4.6%; diarrhoea 5.8% vs 3.5%). Angiotensin converting enzyme 2 and virus nucleocapsid protein were detected in gastrointestinal epithelial cells, and infectious virus particles were isolated from faeces. Faecal PCR testing was as accurate as respiratory specimen PCR detection. In 36% (5/14)‐53% (39/73) faecal PCR became positive, 2‐5 days later than sputum PCR positive. Faecal excretion persisted after sputum excretion in 23% (17/73)‐82% (54/66) patients for 1‐11 days. Conclusions Gastrointestinal symptoms are common in patients with COVID‐19, and had an increased prevalence in the later stage of the recent epidemic in China. SARS‐CoV‐2 enters gastrointestinal epithelial cells, and the faeces of COVID‐19 patients are potentially infectious.