key: cord-0769978-5ks7pjfc
authors: Noverón, Nancy Reynoso; Peralta, Liliana Pérez; Compte, Diana Vilar; Montalvo, Luis Alonso Herrera; Pineda, Sarahí R Gallardo; Gómez, Adriana Areli Gudiño; Vega, Oscar Antonio Ramírez; Gutiérrez, Rodrigo Cáceres; Miranda, Alfredo Hidalgo; Vargas, Alfredo Mendoza; Martínez, Daniel de la Rosa; Juárez, Patricia Cornejo; García, Abelardo A Meneses
title: SARS-CoV-2 positivity rates in asymptomatic workers at a cancer referral center in Mexico City: a prospective observational study in the context of adapting hospitals back to regular practice
date: 2021-09-20
journal: Am J Infect Control
DOI: 10.1016/j.ajic.2021.09.013
sha: bc065f6fc365256c767de68b97db04637a8ee697
doc_id: 769978
cord_uid: 5ks7pjfc

BACKGROUND: : Healthcare workers are at increased risk of SARS-CoV-2 infection. The positivity rates in hospitals that do not receive patients with COVID-19, such as the National Cancer Institute (INCan) in Mexico, and the associated factors are unknown. OBJECTIVE: : To assess the incidence and factors associated with SARS-CoV-2 infection in health workers at INCan. METHODS: : A cohort study of 531 workers who were followed for 6 months. RT-PCR analysis of saliva and nasopharyngeal swab samples were used in the baseline and to confirm cases during follow-up The incidence rate ratio was calculated according to the measured characteristics and the associated factors were calculated using logistic regression models. RESULTS: : Out of 531 workers, 9.6% tested positive for SARS-CoV-2, Being male (RR: 2.07, 95% CI: 1.1-3.8, p=0.02), performing administrative tasks (RR: 1.99, 95% CI: 1.0-3.9, p=0.04), and having relatives also working at INCan (RR: 3.7, 95% CI: 1.4-9.5, p<0.01) were associated with higher positivity rates. DISCUSSION: : Incidence of positive cases in health workers were similar to that reported in non-COVID hospitals from other countries. CONCLUSIONS: : Even though active surveillance helped to detect a significant number of asymptomatic infections, it is still necessary to reinforce preventive measures in non-medical staff to prevent nosocomial transmission.

Mexico is one of many countries whose health care systems collapsed due to the COVID-19 pandemic (1) (2) . Further, Mexican health care workers experienced the highest COVID-19 death rate worldwide (3.8%) (3), posing a serious challenge to health authorities attempting to prevent nosocomial transmission.

During this health care crisis, 33 secondary and tertiary public hospitals in Mexico were converted to treat COVID-19 patients. Meanwhile, other facilities, such as the National Cancer Institute (INCan in Spanish), continued to treat patients with cancer and were called "non-COVID hospitals" (4); specifically, INCan set up an intensive care unit (ICU) for treatment of COVID-19 patients in an exclusive ward with eight intensive care beds and 18 additional beds. The present study aims to 6 assess the incidence of infection with SARS-CoV-2, the virus that causes COVID-19, in health workers at INCan and their associated risk factors.

A prospective open cohort study of health care workers at INCan was conducted between May and October 2020. All subjects gave their consent to participate. The present study was conducted in accordance with the Helsinki Declaration and approved by the INCan Research Ethics Committee (CEI/1479/20) (020/005/DII).

The surveillance model followed the "Standard guideline for laboratory and epidemiological surveillance of COVID-19" issued by the Secretariat of Health (5) .

INCan is a 133-bed teaching hospital for adolescents and adult patients with cancer, and it employs 2,922 individuals. During the study period, 165 (5.64%) health care workers were involved in frontline activities related to COVID, 2122 were involved in non-COVID clinical wards or clinical duties (72.62%), and 635 (21.17%) were in administrative jobs with non-direct patient contact; 67% were women, and 33% were men, with a mean age of 45. During the pandemic, our institution suspended in-person academic and teaching activities, a respiratory triage area was installed for patients and workers, and the flow of patients was reduced. In addition, medical consultations, laboratory studies and office activities were rescheduled. All workers ≥ 65 or with comorbidities (diabetes mellitus, obesity, arterial hypertension, chronic lung disease or cancer) or those who were 7 pregnant ceased work indefinitely to safeguard their health and prevent severe illness due to SARS-CoV-2 infection.

Asymptomatic health care workers at INCan were invited to participate. We excluded subjects who had a history of symptoms consistent with COVID-19 and a positive rapid or RT-PCR test. Every two weeks, they were asked to fill out a questionnaire and give blood samples (to measure antibodies whose analysis is still under development), as well as saliva and nasopharyngeal swabs to confirm suspected cases. Workers who did not attend at least two consecutive follow-up visits were eliminated from the analysis.

During the baseline visit, participants completed an online questionnaire on SARS-CoV-2 exposure. The questionnaire included sociodemographic and clinical variables, as well as data representing higher levels of exposure. The questionnaire was then administered every 5 days for 6 months.

The definitions of suspected and confirmed SARS-CoV-2 cases were adopted from the Secretary of Health in Mexico, as well as measures for epidemiological surveillance, disease prevention, health risk control, COVID-19 precautions, isolation definitions, contact studies and sampling procedures according to the epidemiological surveillance strategies of our country (5) . Suspicious cases were identified via the questionnaire throughout follow-up; in these cases, an RT-PCR 8 test was performed on a saliva sample and in nasopharyngeal swab to confirm the case (an analysis of our group of researchers showed a concordance of 95.2% (kappa 0.852, p= 0.0001)) (6).

Nasopharyngeal swab and saliva samples were collected from all participants at the beginning of the study to detect SARS-CoV-2 through RT-PCR; subsequently, saliva samples and nasopharyngeal swabs were collected only in suspicious cases (by symptoms or contact with confirmed cases). A trained physician performed the sample collection with a flexible swab that was inserted into both nostrils until reaching the posterior nasopharynx of the patient, and it was then withdrawn after several seconds. The swabs were placed in 3 ml of sterile viral transport medium and deposited into a single viral transport tube.

The saliva sample collection was carried out using an Oragene collection tube, in which 5 ml of saliva from each patient was deposited without any stimulation; the patients were asked not to perform oral hygiene or rinse their mouths before sampling.

Both the saliva sample and the nasopharyngeal swab were processed for viral RNA extraction and RT-PCR for virus detection. The concordance between the saliva sample and the swab was analyzed. In case of disagreement, the result obtained through the nasopharyngeal swab was considered definitive. 

Descriptive analysis included measures of central tendency and dispersion of sociodemographic and clinical characteristics depending on the type of variables and their distribution. We estimated the incidence rate (IR) of SARS-CoV-2 infection by dividing the number of new PCR-confirmed cases by the person-time at risk, and the incidence rate ratio (IRR) was calculated between exposure categories. We performed a logistic regression model using variables potentially associated with SARS-CoV-2 positivity rates based on their statistical significance and biological plausibility. The statistical analysis was performed using STATA v.14.

Of the 544 workers who agreed to participate, 13 participants were eliminated, 2 withdrew consent, and 11 were lost to follow-up (they did not attend at least two follow-up visits), leaving a final sample of 531 workers who underwent a total of 1,278 RT-PCR tests and nasopharyngeal swabs. Figure 1 The mean age of the 531 health workers assessed was 40.5±11.3 years; 72.3% were women, 27.6% were men, and 9.6% tested positive for SARS-CoV-2 during the study.

Of all participants, 68% were health care professionals having direct contact with patients, 59.7% commuted to work by car, 60% lived with fewer than three people, and 55% had contact with at least one confirmed positive case. The workplace was referred to as the source of contact by 90.3% of those who had contact with at least one confirmed positive case. Most participants wore masks at work (97.2%) and reported to perform daily activities out of the office and home within the past month (64.9%). A significant number of workers had relatives also working at INCan (26.5%).

Obesity was the most common comorbidity (26.1%), followed by hypertension The clinical, sociodemographic and risk data for SARS-CoV-2 of the subjects included in this study are provided in Table I . 

The following variables were significantly associated with a higher likelihood of SARS-CoV-2 infection: being male (OR: 2.07, 95% CI 1.11-3.86), performing administrative duties (OR: 1.99, 95% CI 1.00-3.96), and having relatives also employed at INCan (OR: 3.76, 95% CI 1.47-9.57). All of these variables adjusted by living with more than 3 people and contact with a positive case are shown in Table III . (9), which could be true in our sample due to widespread mask-wearing, a younger mean age, and fewer comorbidities.

Our study revealed that being male was associated with a higher risk of SARS-CoV-2 positivity (RR: 2.07, 95% CI, p=0.02), which is consistent with sociocultural and biological factors related to molecular and cell markers that make men susceptible to infection, severe disease, and higher mortality (10) (11) . The number of women in our study was higher than that of men, so we do not consider that the (14) . Training should be provided to health workers whose job descriptions make them less familiar with infection prevention protocols, especially after collecting evidence on the impact of case detection and the use of personal protective equipment to reduce transmission (15).

The present study drew on the experience of one of the most important hospitals not focused on COVID in Mexico. Our findings will be useful in improving protocols and meeting future challenges posed by this pandemic, especially in the context of cancer treatment in hospitals

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