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The contact tracing and subsequent quarantining of health care workers (HCWs) are essential to minimizing the further transmission of SARS-CoV-2 infection and mitigating the shortage of HCWs during the COVID-19 pandemic situation.
This study aimed to assess the yield of contact tracing for COVID-19 cases and the risk stratification of HCWs who are exposed to these cases.
This was an analysis of routine data that were collected for the contact tracing of COVID-19 cases at the All India Institute of Medical Sciences, Bhubaneswar, in Odisha, India. Data from March 19 to August 31, 2020, were considered for this study. COVID-19 cases were admitted patients, outpatients, or HCWs in the hospital. HCWs who were exposed to COVID-19 cases were categorized, per the risk stratification guidelines, as high-risk contacts or low-risk contacts
During contact tracing, 3411 HCWs were identified as those who were exposed to 360 COVID-19 cases. Of these 360 cases, 269 (74.7%) were either admitted patients or outpatients, and 91 (25.3%) were HCWs. After the risk stratification of the 3411 HCWs, 890 (26.1%) were categorized as high-risk contacts, and 2521 (73.9%) were categorized as low-risk contacts. The COVID-19 test positivity rates of high-risk contacts and low-risk contacts were 3.8% (34/890) and 1.9% (48/2521), respectively. The average number of high-risk contacts was significantly higher when the COVID-19 case was an admitted patient (number of contacts: mean 6.6) rather than when the COVID-19 case was an HCW (number of contacts: mean 4.0) or outpatient (number of contacts: mean 0.2;
Contact tracing and risk stratification were effective and helped to reduce the number of HCWs requiring quarantine. There was also a decline in the number of high-risk contacts during the study period. This indicates the role of the implementation of hospital-based, COVID-19–related infection control strategies. The contact tracing and risk stratification approaches that were designed in this study can also be implemented in other health care settings.
With 44 million confirmed cases and over 1 million confirmed deaths affecting all countries across the world, the COVID-19 pandemic is currently the largest pandemic of the century [
By September 17, 2020, countries reported to the World Health Organization (WHO) that 14% of COVID-19 cases were health care workers (HCWs) [
Contact tracing is a time- and resource-intensive exercise for community settings as well as hospital settings. However, it is one of the most important methods for infectious disease prevention. In our hospital, we used different methods that were described in literature to identify people who were exposed to COVID-19 cases, like the use of closed-circuit television (CCTV) footage and duty rosters and the passive reporting of contacts by departments and via telephonic inquiry. Contact tracing by using data extracted from administrative and clinical databases, such as electronic medical records, or by using CCTV footage (a real-time locating system) has been reported previously [
Although the processes of contact tracing, risk stratification, and quarantine may help to reduce the transmission of infection, it is not clear whether these processes help with reducing staff shortages in an already overwhelmed health system of a resource-constrained setting. A systematic review of 22 studies concluded that an integrated strategy for contact tracing, screening, quarantine, and isolation has the potential to reduce the incidence of SARS-CoV-2 infection [
In our hospital, which caters to both patients with COVID-19 and other patients, we adopted the contact tracing and risk stratification approaches described by the WHO, CDC, and MoHFW to categorize COVID-19–exposed HCWs as high-risk contacts or low-risk contacts. This study was conducted to assess the yield of hospital-based contact tracing for patients and HCWs who tested positive for COVID-19 and the risk stratification of COVID-19–exposed HCWs in the hospital—a statutory body under the aegis of the MoHFW of the Government of India. We also compared the risk categorizations of different areas (COVID-19 and non–COVID-19 areas) and different categories of index cases (outpatient department [OPD], inpatient department [IPD], and HCW cases) to assess the variations.
This study was a process evaluation of our routine contact tracing and risk stratification mechanisms at the study site. Data from March 19 to August 31, 2020, were collected.
This study was conducted at the All India Institute of Medical Sciences (AIIMS), Bhubaneswar, which is a 960-bed tertiary care teaching hospital located in Bhubaneswar, the capital city of Odisha (an eastern state of India).
Patients who were admitted to the hospital were screened for COVID-19, as per the screening algorithm depicted in
Algorithm of the COVID-19 testing strategy for patients admitted to the hospital. AIIMS: All India Institute of Medical Sciences; ICU: intensive care unit; ILI: influenza-like illness; OPD: outpatient department; RT-PCR: reverse transcription-polymerase chain reaction; TEM: trauma and emergency.
Various training programs were conducted to train all cadres of HCWs in the proper use of personal protective equipment (PPE), hand hygiene measures, and other infection control practices. The use of various types of PPE in different clinical areas and hospital premises was guided by MoHFW protocols and upgraded or modified based on feedback from the contact tracing and infection control teams. Advisories were issued to all HCWs at periodic intervals for PPE compliance and infection control measures. We also introduced various behavioral and regulatory interventions to promote COVID-19–appropriate behaviors, such as a monetary penalty for not using a mask in the hospital and residential campuses.
As per the testing strategy outlined in
SARS-CoV-2 testing strategy for the health care workers after contact tracing.
Contact tracing was initiated by a team that was dedicated to performing contact tracing immediately after intimation from the diagnostic laboratory. Initially, contact tracing was done by physically visiting the clinical areas, personally interviewing the HCWs involved in patient care, reviewing medical records of patients and duty rosters, and viewing CCTV footage. However, this strategy was modified, due to the increase in the number of COVID-19 cases, to include a passive mechanism for contact tracing. In the later phase (from July 15 onward), the contact tracing team (CTT) directed the concerned departments to provide a list of all HCWs who had possibly come in contact with confirmed COVID-19 cases in a prescribed format. Upon obtaining the list of COVID-19–exposed HCWs, the CTT contacted each HCW telephonically to elicit histories related to the durations and types of exposures, the procedures performed on the patient, and the use of PPE during exposures. Data were collected by using a semistructured interview schedule. For cases of contact tracing related to an HCW who tested positive for COVID-19, histories related to interactions that occurred during duty break hours, during meals, and in places where HCWs are likely to be less cautious in terms of mask usage were probed during contact tracing. Exposures the occurred during the last 14 days from the date of a positive report were considered for contact tracing. The numbers of contacts were separately calculated for each positive case.
Risk categorizations (low-risk exposure and high-risk exposure) based on the criteria adopted from the WHO, CDC, and MoHFW guidelines are given in
Touched body fluids of a patient (eg, touching respiratory tract secretions, blood, vomit, saliva, urine, and feces; being coughed on; touching used paper tissues with a bare hand; etc)
Had direct physical contact with the body of a patient, including during physical examinations without personal protective equipment
Touched or cleaned the linens, clothes, or dishes of a patient
Lives in the same household as a patient
Anyone who was in close proximity (within 1 meter) to a confirmed COVID-19 case and did not take precautions
Passengers (ie, those in a vehicle) who were in close proximity (for more than 6 hours) to a symptomatic person who later tested positive for COVID-19
Shared the same space (worked in same room or a similar situation) but did not have a high-risk exposure to a confirmed case of COVID-19
Traveled in the same environment (bus, train, flight, or any other mode of transit) but did not have a high-risk exposure
Ethical approval to conduct this study was obtained from the Institutional Ethics Committee of AIIMS, Bhubaneswar (reference number: T/IM-NF/CMFM/20/76). Individual participant consent was not obtained, as contact tracing was a regular process for risk stratification among the HCWs. All HCWs were instructed by the hospital authorities to cooperate with the CTT.
Statistical analyses were conducted by using Microsoft Excel 2013 and SPSS version 22.0 (IBM Corporation). Descriptive statistics were presented as means with SDs and percentages with 95% CIs. The mean number and SD of high-risk contacts and low-risk contacts among the types of patients (ie, admitted patients in a COVID-19 area, admitted patients in a non–COVID-19 area, outpatients, and HCWs) were compared. A
Our analysis included data related to 360 COVID-19 cases that were reported during the study period, which included 240 (66.7%) admitted patients and IPD patients, 29 (8.1%) OPD patients, and 91 (25.3%) HCWs. Of the 269 IPD and OPD patients, 163 (60.6%) were admitted directly to a COVID-19 area, 97 (36.1%) were admitted in a non–COVID-19 area, and the rest (n=9, 3.3%) had stayed in both COVID-19 and non–COVID-19 areas (
Distribution of patients who tested positive for COVID-19 in the hospital from March to August 2020.
Types of patients and areas | Patients, n (%) | ||
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Inpatient department patients | 240 (66.7) | |
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Outpatient department patients | 29 (8) | |
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Health care workers | 91 (25.3) | |
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COVID-19 area | 163 (60.6) | |
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Non–COVID-19 area | 97 (36.1) | |
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Both | 9 (3.3) |
The CTT identified 3411 HCWs who were exposed to any COVID-19 case in the hospital. After risk categorization, 26.1% (890/3411) of HCWs were identified as high-risk contacts, and 73.9% (2521/3411) were identified as low-risk contacts. Within 14 days of exposure to a COVID-19 case, 34 out of the 890 high-risk contacts (3.8%; 95% CI 2.7%-5.2%) and 48 out of the 2521 low-risk contacts (1.9%; 95% CI 1.4%-2.5%) tested positive for SARS-CoV-2 infection. However, among the low-risk contacts, only symptomatic HCWs were tested, and the test positivity rate among the symptomatic low-risk contacts was 48 out of 1583 (3.03%; 95% CI 2.24%-4.00%).
The mean number of high-risk contacts was 15.8 (SD 18.3) when a COVID-19 case was admitted in a non–COVID-19 area and 4.0 (SD 5.6) when the COVID-19 case was an HCW. The mean number of high-risk contacts per patient was <1 if a patient was admitted in a COVID-19 area or was provided with services on an outpatient basis. The difference in the mean numbers of high-risk contacts among the different groups was statistically significant (
Comparison of the average number of high-risk and low-risk contacts, with respect to the type of index case, in the hospital from March to August 2020.
Types of patients and areas | Number of cases | Number of contacts, mean (SD) | ||||||||||
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4.741 (2)c | .009 | |||||||||
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Inpatient department patients | 240 | 6.61 (13.895) |
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Outpatient department patients | 29 | 0.22 (0.698) |
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Health care workers | 91 | 4.02 (5.653) |
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8.527 (2)c | .002 | |||||||||
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Inpatient department patients | 240 | 10.81 (11.754) |
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Outpatient department patients | 29 | 3.07 (2.541) |
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Health care workers | 91 | 8.12 (6.789) |
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−10.853 (258)d | <.001 | |||||||||
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COVID-19 area | 163 | 0.27 (1.207) |
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Non–COVID-19 area | 97 | 15.84 (18.268) |
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−7.803 (258)d | <.001 | |||||||||
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COVID-19 area | 163 | 5.93 (5.544) |
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Non–COVID-19 area | 97 | 16.19 (15.188) |
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aA 2-tailed unpaired
bANOVA: analysis of variance.
cAnalysis of variance test value.
d2-tailed unpaired
A significant decline in the mean number of high-risk contacts was reported over the study period (
A: Average number of contacts when the COVID-19 case was an admitted patient (March to August 2020). B: Average number of contacts when the COVID-19 case was a health care worker (March to August 2020). C: Average number of contacts when the COVID-19 case was admitted in a COVID-19 area (March to August 2020). D: Average number of contacts when the COVID-19 case was admitted in a non–COVID-19 area (March to August 2020).
Interviews with HCWs, which were conducted during contact tracing, revealed that common causes for a high-risk exposure during the provision of clinical care were the inadequate use of PPE and the nonpracticing of hand hygiene measures after having direct contact with a patient. Further, HCWs who tested positive for COVID-19 indicated that social interactions during meals and at nursing stations during duty hours, handover, travel, and the act of staying together were major contributing factors (24/91, 26%).
Our forward contact tracing of 360 COVID-19 cases, who were either patients or HCWs, resulted in the identification of 3411 exposures. After risk stratification, 26.1% (890/3411) of HCWs were categorized as high-risk contacts, and 73.9% (2521/3411) were categorized as low-risk contacts. Of the 890 high-risk contacts and 2521 low-risk contacts, 34 (3.8%) and 48 (1.9%), respectively, tested positive for SARS-COV-2 infection. We also observed a gradual decline in the average number of high-risk contacts over a period of time. HCWs were more likely to be exposed to SARS-CoV-2 infection when it was diagnosed among HCWs and patients who were admitted in a non–COVID-19 area.
A few studies from India have also reported similar proportions of high-risk contacts after risk stratification. According to a study conducted by Agarwal et al [
We also observed a clear difference in the COVID-19 test positivity rates between high-risk contacts and low-risk contacts (34/890, 3.8% vs 48/2521, 1.9%), which demonstrated the effectiveness of the risk stratification strategy. However, among the low-risk contacts who were tested, the test positivity rate was 3.03% (48/1583). Due to the very high number of contacts, all of the high-risk contacts and only the symptomatic low-risk contacts were tested. Moreover, low-risk contacts could have been exposed to SARS-CoV-2 infection outside of the hospital because, unlike high-risk contacts, they were not quarantined and continued to work. The effectiveness of contact tracing was observed in previous studies [
The mean number of high-risk contacts was highest when a patient was admitted in the non–COVID-19 area (number of contacts: mean 15.8) rather than when a patient was admitted in a COVID-19 area (number of contacts: mean 0.27). The mean number of high-risk contacts was higher in non–COVID-19 areas probably because the recommended level of protection in non–COVID-19 areas is different from that of COVID-19 areas. Similarly, HCWs’ attitudes toward following the protocol might be better in COVID-19 areas due to the higher perceived risk. In COVID-19 areas, HCWs were completely equipped with PPE. In the non-COVID-19 area however, they were only equipped with surgical masks, N95 masks, and gloves, as per the guidelines proposed by the MoHFW, WHO, and CDC, and admitted patients were not suspected of SARS-CoV-2 infection [
There was also a significant reduction in the number of high-risk contacts for all categories of COVID-19 cases (ie, cases in COVID-19 areas, cases in non–COVID-19 areas, IPD cases, OPD cases, and HCW cases) over the study period (
The CTT also provided regular feedback (based on inquiries from COVID-19–exposed HCWs) to the hospital administration to augment infection control measures, identified areas in which frequent breaches in protocols occurred, and suggested a mechanism for reducing the number of exposures to COVID-19. Apart from quarantine, regular feedback–based action might have helped to reduce the number of exposures to SARS-CoV-2 infection in the hospital.
Since multiple strategies were used, such as visiting the clinical area, conducting personal interviews with the HCWs, reviewing medical records, and viewing CCTV footage, we believe that all of the possible contacts were listed, tracked, and categorized properly, as these strategies were performed by trained personnel and verified by experts. Thus, the quality of the data was expected to be satisfactory. Testing for COVID-19 was performed in an Indian Council of Medical Research–approved testing center via RT-PCR, which is considered to be the gold-standard test. All high-risk cases were continuously monitored for 14 days after their most recent exposure to SARS-CoV-2 infection, and COVID-19 testing was performed on the seventh day.
The categorization of risk was based on the histories of the contacts, which may have increased the chances of social desirability bias affecting our results. Our data might have included misinformation, as hospital staff might have deliberately wanted to be categorized as high-risk contacts, so that they could be quarantined for 14 days and still be fully paid. There was also a chance that HCWs recalled incorrect information. Sometimes, the HCWs failed to remember patients’ SARS-CoV-2 infection status and their own PPE status during patient care. Further, low-risk contacts were not routinely tested unless they were symptomatic. Therefore, we could have missed some cases, as many COVID-19 cases remain asymptomatic or paucisymptomatic.
Contact tracing and risk stratification were effective and helped to reduce the number of HCWs requiring quarantine. There was a decline in the number of high-risk contacts during the study period. This indicates the role of the implementation of hospital-based COVID-19–related infection control strategies. The findings obtained during contact tracing might also be beneficial for developing appropriate and strategic infection control measures. The contact tracing and risk stratification approaches that were designed in this study can also be implemented in other health care settings.
All India Institute of Medical Sciences
closed-circuit television
Centers for Disease Control and Prevention
contact tracing team
health care worker
inpatient department
Ministry of Health and Family Welfare
outpatient department
personal protective equipment
reverse transcription-polymerase chain reaction
World Health Organization
We are grateful to the health care workers and the hospital administration for their cooperation during contact tracing.
DP Sahoo, AKS, BKP, and GB conceptualized this study. DP Sahoo, AKS, BKP, DP Sahu, SKP, and GB developed the methodology. DP Sahoo, AKS, BKP, DP Sahu, and SKP curated the data. DP Sahoo, SKP, DP Sahu, BM, BB, AD, GSD, LA, SMA, JN, SP, RA, BKS, S Sahu, and S Sahoo performed the investigation. DP Sahoo and AKS conducted the formal analysis. AKS, BKP, and GB supervised this study. DP Sahoo and AKS wrote the original draft. BKP, DP Sahu, SKP, GB, BM, BB, AD, GSD, LA, SMA, JN, SP, RA, BKS, S Sahu, and S Sahoo wrote, reviewed, and edited this paper.
None declared.