key: cord-0845470-dmvqjriu authors: Galan, I.; Velasco, M.; Casas, M. L.; Goyanes, M. J.; Rodriguez-Caravaca, G.; Losa, J. E.; Noguera, C.; Castilla, V.; investigators, Working Group Alcorcon COVID-19 title: SARS-CoV-2 SEROPREVALENCE AMONG ALL WORKERS IN A TEACHING HOSPITAL IN SPAIN: UNMASKING THE RISK. date: 2020-05-29 journal: nan DOI: 10.1101/2020.05.29.20116731 sha: ba107b533a1bf5feaed346f290a1e96a0bade93c doc_id: 845470 cord_uid: dmvqjriu Background: Health-care workers (HCW) are at increased risk for SARS-CoV-2 infection, but few studies have evaluated prevalence of antibodies against SARS-CoV-2 among them. Objective: To determine the seroprevalence against SARS-CoV-2 in all HCW. Methods. Cross-sectional study (April 14th- 27th , 2020) of all HCW at Hospital Universitario Fundacion Alcorcon, a second level teaching hospital in Madrid, Spain. SARS-CoV-2 IgG was measured by ELISA. HCW were classified by professional category, working area, and risk for SARS-CoV-2 exposure. Results: Among 2919 HCW, 2590 (90.5%) were evaluated. Mean age was 43.8 years (SD 11.1) and 73.9% were females. Globally, 818 (31.6%) workers were IgG positive, with no differences for age, sex or previous diseases. Among them, 48.5% did not report previous symptoms. Seropositivity was more frequent in high (33.1%) and medium (33.8%) than in low-risk areas (25.8%, p=0.007), but no difference was found for hospitalization areas attending COVID-19 and non-COVID-19 patients (35.5 vs 38.3% p=NS). HCW with a previous SARS-CoV2 PCR positive test were IgG seropositive in 90.8%. By multivariate logistic regression analysis, seropositivity was associated with being physicians (OR 2.37, CI95% 1.61-3.49), nurses (OR 1.67, CI95% 1.14-2.46), or nurse- assistants (OR 1.84, CI95% 1.24-2.73), HCW working at COVID-19 hospitalization areas (OR 1.71, CI95% 1.22-2.40), non-COVID-19 hospitalization areas (OR 1.88, CI95% 1.30-2.73), and at the Emergency Room (OR 1.51, CI95% 1.01-2.27) Conclusions: Seroprevalence uncovered a high rate of infection previously unnoticed among HCW. Patients not suspected of having COVID-19 as well as asymptomatic HCW may be a relevant source for nosocomial SARS-CoV-2 transmission. COVID-19 is a disease caused by a new human coronavirus (SARS-CoV-2) that emerged in Wuhan, China, in late 2019 1 . In Spain, the first case of SARS-CoV-2 was identified on January 31 st imported from Germany. Since that time, a sharp increase in the number of cases has pushed the capacity of healthcare system in Madrid beyond the limit 2 . More than 60.000 patients were attended in Madrid`s hospitals during March and April 2020 2 . As the pandemic accelerated, access to personal protective equipment (PPE) for health workers was a key concern, moreover because of PPE shortages 4 . Health-care workers (HCW) are at increased risk for infection, and specific requirements for their protection are advisable to ensure the functioning of the healthcare system 5 . Indeed, in Spain, more than 26.000 health care workers have been infected and at least 41 had died 4 . Alongside concerns for the healthcare workers personal safety, anxiety about transmitting the infection to their relatives and patients adds another stress to HCW. At this time, it is known that SARS-CoV-2 human to human transmission occurs during the presymptomatic stage through droplets or direct contact [6] [7] [8] . The possibility of presymptomatic transmission increases the challenges of containment measures [9] [10] [11] . Moreover, according to two studies, presumed hospital-related transmission of SARS-CoV-2 was suspected in 41% and 35% of patients 10, 12, 13 . Nosocomial transmission may originate from patients (where protective measures are usually strict), but also from asymptomatic HCW (where protective measures may be more relaxed or simply non-existing). Little is known about hospital HCW seroprevalence for SARS-CoV-2. Rates from other coronavirus epidemic such as MERS and SARS range between 2.3% and 20% of subclinical infection [14] [15] [16] . Nosocomial transmission has been recognized as an important amplifier in epidemics of both SARS and Middle East respiratory syndrome [17] [18] [19] . Serological surveillance of exposed individuals allows to estimate the individual risk. This approach is essential since the safety of health-care workers must be ensured. Screening all health-care workers for SARS-CoV-2 in the hospital would be helpful to maintain the welfare of the staff and to enable identification of infected health-care workers. Our objective was to evaluate the prevalence of immunoglobulin G (IgG) against SARS-CoV-2 among all the employees of a second level teaching hospital in the south of Madrid. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted May 29, 2020 We measured serum IgG antibody by an enzyme-linked immunosorbent assay (ELISA) IgG2 using a SARS-CoV-2 S spike and Nucleocapsid recombinant antigens (Diapro (Palex), Italy), to screen for the presence of human anti-SARS-CoV-2 IgG. This assay (CE approved) was used according to the manufacturer's protocol. Reported sensitivity of the assay by the manufacturer was 98% (Supplement 2) . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. HCW with positive IgG and presence of symptoms older than 14 days were assumed to be infected but no longer contagious. Those with positive IgG and symptoms in the past 14 days were considered as active infected and potential contagious and underwent PCR examination. If PCR results were positive, they were discharged. HCW with IgG negative were considered susceptible to SARS-CoV-2 infection 21 . Asymptomatic workers were not routinely tested with PCR, but such test was performed for persons with self-reported symptoms, and the report was voluntary. Data are reported as mean (± SD), median (IQR) or percentage as appropriate. Categorical variables were compared using Pearson's X2 test or Fisher exact test. Continuous variables were analyzed using the Student t-test. A univariate analysis was carried out to find independently associated risk factors for positive IgG. A multivariate logistic regression model evaluated the association between risk factors and positive IgG was assessed by reference to odds ratio (OR). Statistical analysis was performed, with hypothesis testing based on a two-tailed test of significance and we considered statistical significance P<0.05 with the Statistical Package for Social Sciences (SPSSPC v 20 Illinois USA) Study approval / Ethics . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . https://doi.org/10.1101/2020.05.29.20116731 doi: medRxiv preprint All participants enrolled into the study voluntarily, and written informed consent was required to use the data for analysis. Participation in the study or results were not reported to the employer. The study protocol was approved by the HUFA independent ethics research committee (reference number 20/69). We stated that results not would be used to generate an immunological passport in the hospital 22 . . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . https://doi.org/10.1101/2020.05.29.20116731 doi: medRxiv preprint All 2,919 HCW HUFA were invited to participate in the study between April 14-27, 2020. Among them 278 (9.5%) workers did not come to be tested because sick leave, work at home, or declined the invitation ( figure 1 ). In addition, 51 HCW (1.8%) refused consent to use their data for investigational purposes and were removed from the analysis. Thus, data of a total of 2,590 (98%) HCW were analyzed. They were 1,915 females, (73.9%) and mean age was 43.8 (SD 11.1) years. Previous relevant clinical condition was present in 998 HCW (38.5%), distributed as follows: tobacco use 21%, chronic lung disease or asthma 8%, obesity 6.0%, high blood pressure 6.9%, diabetes mellitus 2.1% and other cardiovascular diseases 2.0% (Table 1) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . https://doi.org/10.1101/2020.05.29.20116731 doi: medRxiv preprint DISCUSSION This is the first study of the SARS-CoV-2 seroprevalence of all HCW, regardless whether they were or not direct employee of the hospital. We found a relatively high proportion (30%) of HCW with a positive IgG for SARS-CoV-2. A recent study from Spanish population showed a national prevalence of 5%, but 11% in Madrid 23 . A partial explanation for a higher prevalence at our hospital is the higher exposition to the virus in the city of Alcorcón. Data from Madrid Regional Government shows that Alcorcón had a slightly higher incidence of COVID-19 than the region of Madrid 24 . Furthermore, a recent study from a large hospital in Barcelona showed a prevalence in a sample of HCW of 11.6%, doubling the seroprevalence of the general population 25 , strengthening the notion of hospitals as a places of risk for SARS-Co2 infection among workers. Unsurprisingly, external workers (23.9%) and non-clinical workers (25.8%) had lower seroprevalence than average 26 , although still much higher than the general population in Madrid 23 . These data suggest a role for nosocomial transmission also for non-clinical workers 27, 28 Regarding clinical workers (all of them direct employees of the hospital), the rate of positive IgG was virtually identical among workers with direct contact with COVID-19-patients and those taking care of non-COVID-19 patients, as it has been reported in other settings 20 . Some have proposed that workers with no direct contact with COVID-19 could have been infected in the population (in a context in which the actual seroprevalence in the population was unknown) 20 . Our data argue against it: clinical worker in non-COVID areas become seropositive likely because of in-hospital contact, either from asymptomatic patients or colleagues. These data suggest that the non-COVID-19 clinical areas are indeed an unrecognized potential source for COVID-19 infection among workers 27 . A recent meta-. CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . https://doi.org/10.1101/2020.05.29.20116731 doi: medRxiv preprint analysis estimates that nosocomial transmission is the source of SARS-CoV-2 infection in about 44% of cases 29 . This estimation is further increased up to almost 90% of cases in a mathematical model. 30 Since universal COVID-19 screening has not been a usual practice implemented it is conceivable that a substantial proportion of so-called non-COVID-19 patients may be actually subclinical or unnoticed COVID-19 cases 31,32 . Our results are in agreement with a high rate of nosocomial transmission reported among workers in a dialysis unit in New York 33 . These data emphasize the need for universal screening of all in-hospital patients as recommend World Health Organisation 34-36 and we are already implementing. A similar proportion of seropositivity among clinicians taking direct care of COVID-19 patients suggest that the isolation protocols and PPE appear sufficient to prevent high levels of nosocomial transmission in our setting 13, 37 . Of note, critical care workers had one of the lowest seropositivity rates in our study. Indeed, our hospital prioritized the use of the best available PPE for critical care units, where virtually all patients were COVID-19 at the peak of the epidemic 38 . The clinical spectrum of COVID-19 in our workers resembles that described for the general population: about half of them are asymptomatic or paucisymptomatic [39] [40] [41] [42] [43] and less than 60% had fever (figure 3). That means that most infected workers remain undetected unless there is a universal screening 44, 45 . In retrospect, about 50% of seropositive workers attending to the serology study recalled minor symptoms that did not prompt a request for OHU evaluation. Thus, only about one fourth of IgG positive workers were fully asymptomatic, as reported in other studies 31, 33 . Regarding workers with overt symptoms suggesting COVID-19 disease most of them (83%) had a mild disease that could be managed in the outpatient setting. About . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . https://doi.org/10.1101/2020.05.29.20116731 doi: medRxiv preprint 6% required ER visit and 3% required hospital admission. There were no deaths. This is hardly surprisingly since there is no elder population among active workers 10 . To prevent nosocomial transmission both patients and health care workers should be screened for SARS-CoV-2 infection regardless of the absence of typical symptoms for COVID-19 disease 45 as asymptomatic transmission is being increasing recognized as very relevant in SARS-CoV-2 spread. 9, 27, 46 . Our study has some limitations that deserve consideration. First, we do not have data about Ig M or concurrent PCR. However, our study was designed to have a picture of past exposure to the virus in all our workers. We did not pursue an evolutionary perspective of the disease. Second, the samples were collected over two weeks, so the interpretation of the prevalence must be related to the average prevalence at that time. Nonetheless, our work has several strengths. First, the quality of the technology we had used seems to be one of the highest sensitivities available (ELISA) [47] [48] [49] . Second, we had a virtually universal representation of all workers of the hospital (90%), including external employees, an evaluation hardly performed. Additionally, we identified the particular function of all employees in a time of changing roles for clinicians in the middle of the crisis. In addition, its close temporal vicinity with the serologic study in the Spanish population allows for a direct comparison. In conclusion, seroprevalence unmasked a high rate of infection previously unnoticed in HCW. Clinical care of COVID-19 unscreened patients is associated with a similar prevalence of SARS-CoV-2 antibodies as the one found in COVID-19 facilities uncovering a relevant source for nosocomial SARS-CoV-2 transmission. In addition, apparently healthy HCW may also be another relevant source for SARS-CoV-2 transmission. HCW testing could reduce in-hospital transmission 50 . Serosurveys in hospitals may be helpful to design strategies to control SARS-CoV-2 epidemic. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . https://doi.org/10.1101/2020.05.29.20116731 doi: medRxiv preprint We thank all workers of the Hospital Universitario Fundación Alcorcón, who bravely and generously faced the COVID-19 epidemic during the months of March and April for their everyday work and cooperation in this study. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . https://doi.org/10.1101/2020.05.29.20116731 doi: medRxiv preprint SUPPLEMENT 1 Previous health conditions: tobacco use, hypertension, obesity, cardiovascular disease, chronic liver disease, chronic lung disease or asthma, chronic renal failure, immunodeficiency, or pregnancy. COVID-19 related symptoms: fever, myalgia, cough, sputum, dyspnea, rhinorrhea, sore throat, diarrhea, anosmia/hyposmia, ageusia/dysgeusia, asthenia, chest pain, headache, syncope, others), SARS-CoV-2 PCR test result as well as the severity of disease when appropriate (out-patient evaluation, ER consultation, hospital admission and clinical outcome. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . https://doi.org/10.1101/2020.05.29.20116731 doi: medRxiv preprint We measured serum IgG antibody by an enzyme-linked immunosorbent assay (ELISA) IgG2 using a SARS-CoV-2 S spike and Nucleocapsid recombinant antigens (Diapro (Palex), Italy), to screen for the presence of human anti-SARS-CoV-2 IgG. This assay (CE approved) was used according to the manufacturer's protocol. Reported sensitivity of the assay by the manufacturer was 98%. The results of the tested samples were determined by calculating the ratio of the optical density (OD) value of the sample to the OD value of the cut-off. (Co) Ratios ≥ 1.1 were considered positive, ratios ≥ 0.9 to < 1.1 were considered borderline, and ratios < 0.9 were considered negative. All assays were run following manufacter´s instructions on the platforms DSX System ( Palex Medical SA) and Triturus ( Grifols Movaco SA). Sensitivity of the assay using samples from 337 workers from our series with results previous positive PCR was 90.8% (manufacture shows 98%). Specificity manufacture's instructions shows that the assay was tested on hundreds of samples collected before the outbreak of COVID-19. A value of >90% was found. Index values considered "borderline" were tested on Strips-module Enzyme Immunoassay for the confirmation of IgG antibodies to COVID-19-19 major antigens. This assay detects IgG antibodies against the SARS-CoV-2: Spike glycoprotein 1, Spike glycoprotein 2 and nucleocapside proteins. A sample is considered for a certain antibody negative S/Co<1, equivocal 1< S/Co<1.2, positive S/Co>1.2. These samples were run on the platform DSX System ( Palex Medical SA). The manufacter´s instructions shows that the assay was tested on hundreds of samples collected before the outbreak of COVID- . A value of >98% was found. About 2% of the reactive "normal" population shows a reactivity to Nucleocapsid. A first minimum study carried . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 29, 2020. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted May 29, 2020. . https://doi.org/10.1101/2020.05.29.20116731 doi: medRxiv preprint Table 2 . Univariate logistic regression Multivariate logistic regression (model 1) Multivariate logistic regression (model 2) Figure 1 . . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted May 29, 2020. . https://doi.org/10.1101/2020.05.29.20116731 doi: medRxiv preprint . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted May 29, 2020. . https://doi.org/10.1101/2020.05.29.20116731 doi: medRxiv preprint CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted May 29, 2020. . 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