Rapid response and mitigation measures in control of COVID-19 cases in an industrial warehouse of Western Maharashtra, India
Shabeena Tawar, G Diva Reddy, Sougat Ray, Naveen Chawla, Swati Garg
Professor, Department of Community Medicine & SSO(H), HQWNC, Mumbai, India
Surg R Adm Naveen Chawla
Professor Pathology and CMO, HQWNC, Mumbai
Source of Support: None, Conflict of Interest: NoneCheck
Introduction: From being declared as Public Health Emergency of International Concern and the transmission dynamics of COVID-19, outbreak control has been the cornerstone of combating COVID-19 cases within communities and clusters. An outbreak investigation of COVID-19 positive cases was conducted in a close community setting at an industrial warehouse which included working and residential areas in the premises, with the aim to break the chain of transmission rapidly and to formulate preventive strategy for dealing with other outbreaks in a community setting. Materials and Methods: This was a study where a rapid outbreak response was carried out after two individuals tested COVID-19 positive. Following the national and local guidelines, immediate decongestion followed by aggressive contact tracing, testing and isolating the cases were done. Results: After the rapid contact tracing exercise, contacts were identified, quarantined and tested. Daily monitoring of the contacts revealed six symptomatic confirmed cases and on testing, 19 asymptomatic contacts were positive. All confirmed cases were immediately admitted to the hospital. Additional two positive cases reported from family contacts. The mean age of the individuals was 46 years. There were 9 individuals with co-morbidities and two individuals developed acute respiratory distress syndrome and expired in the hospital. The secondary attack rate was calculated to be 17.51%. Conclusion: Prompt public health measures by rapid response team, creation of containment zone, contact tracing, early isolation along with daily influenza like illness screening and strict quarantine effectively helped in containment of the outbreak in the population under study.
Keywords: Containment, COVID-19, disinfection, outbreak, quarantine
The COVID-19 pandemic has pushed us all to the precipice with >20 million individuals affected globally. The case fatality rates (CFR) have varied widely between countries ranging from 0.2% in Germany to 7.7% in Italy, with India recording a CFR of 3.6 in April 2020, which decreased to 2.10 in August 20. Aerosolized transmission of COVID-19 presents a unique challenge in infectious disease control. A small percentage of infectious individuals appear to be responsible for disseminating most infectious particles. The transmission of disease occurs through both “droplet particles” and “airborne,” droplet transmission typically occurring in susceptible individuals who are close enough (usually within 03 M) and airborne transmission remaining suspended for a longer time and traveling up to 20 M. However, if susceptible individuals are present close enough, as found in overcrowded, poorly ventilated rooms, the transmission of disease will be rapid. The asymptomatic and presymptomatic transmission along with high infectiousness of the virus has led to the formation of clusters of cases from a single patient. History reminds us that though the 2002 SARS pandemic had endangered several lives, the disease was curtailed by employing strict public health measures, of “wide-net” surveillance, contact tracing and quarantining the contacts, testing and isolating the infected and treating the symptomatic cases.
Outbreak of airborne infectious diseases among humans results from transmission of an organism directly between hosts. When an individual infects, on average, more than one additional individual, then an outbreak can occur. The efficiency of transmission depends on the infectiousness of the infected host (or hosts) and the susceptibility of uninfected individuals who are exposed to infection and depends on host factors like immunity and closeness among the exposed individuals.
Asymptomatic and presymptomatic transmission have confused the world in the struggle towards containing the transmission. However, like other airborne disease transmission, rapid intervention by isolation of cases, tracing and quarantining the contacts, decongesting or reduction of overcrowding, universal use of masks and hygiene measures have been found to be extremely useful in the absence of vaccines and other pharmacological interventions in controlling an outbreak in a defined region., In this retrospective observational study, we have described the occurrence of a COVID-19 outbreak among employees of an industrial warehouse complex and their families and analyzed the effectiveness of rapidly instituted containment measures to control the disease in the population.Materials and Methods
Primary data of all individuals admitted to the hospital in May from the area were obtained from the electronic medical records section of the local health department. The data was collated in excel and analyzed.
Case definitions were based on the World Health Organization (WHO) and the Ministry of Health and Family Welfare (MoHFW) interim guidance documents. Suspect case was defined as a patient with acute respiratory illness (fever and at least one sign/symptom of respiratory disease [e.g., cough, shortness of breath]), and residence in a country/area or territory reporting local transmission of COVID-19 disease during the 14 days before symptom onset. A confirmed case was labeled based on reverse transcriptase polymerase chain reaction (RT PCR) test positive report. Outbreak was defined as two or more patients with COVID-19 when discovered to be linked, and the linkage is established outside of a case investigation and contact tracing. Risk profiling of contacts into high risk and low risk was done based on the MOHFW guidelines. Cases were classified according to the case definition; the proportion of suspected and laboratory-confirmed cases. Self-quarantine. was described as individuals having to remain in their household, maintain social distancing, use a mask, and report about influenza like illness (ILI) symptoms. The secondary attack rate (SAR) was defined as the probability that an infection occurs among susceptible people within a specific group and provides an indication of how social interactions relate to transmission risk.
To study and analyse the time and distribution of cases, an epidemic curve and spot map were plotted. Active surveillance was initiated with the development of the first case and continued for 28 days from the reporting of the last case to assess the effect of the employed control measures and detection of any fresh case.
Control measures instituted on the occurrence of the index case
The study was undertaken in an urban community within the inmates of a warehouse in Western Maharashtra. The setting was that of an industrial warehouse and premises, which included working and residential areas. The local rapid response team (RRT), comprising one public health specialist and three paramedical staff visited the site on detection of the first confirmed case. Verification of diagnosis was made based on RT PCR-positive report of the Index case. Mapping of the affected area by the delineation of containment and buffer zone was done. Three distinct cohorts were identified, as brought out in [Figure 1]. Individuals belonging to Cohort 1 and 2 were men working at the warehouse and living in two different building complexes. The third cohort comprised residential houses. There were 40 individuals in Cohort 1, 46 in Cohort 2, and 52 individuals in Cohort 3. The working men's residential blocks and the family quarters were made into a containment zone, and rest of the area of the industrial warehouse was considered as buffer zone [Figure 1]. As part of the Outbreak investigation, aggressive contact tracing of the index case was undertaken, which revealed 28 individuals as high-risk contacts and 58 as low-risk contacts. Control measures were instituted as per the cluster containment strategy of MOHFW. No movement to and from the warehouse was allowed.
All personnel were placed into strict quarantine and the in-living blocks were decongested to ensure no overcrowding and ample ventilation. Individuals were shifted to another dormitory and few double occupancy rooms to enable a distance of 3 M between each other to discourage droplet and airborne transmission. The meal timing was staggered. Meals were provided in disposable plates outside the dormitories and rooms. Improved nutrition was suggested by way of including foods rich in Vit C, Vit D, and Zinc, including supplementation with multivitamins. Health education was conducted for all to enable acceptance of the occurrence of positive case and the necessity of adherence to control measures.
Primary source tracing of the index case was done after obtaining a detailed history and tracking all his movements 4 days before the onset of symptoms. Testing with RT PCR was carried out as per the MoHFW and WHO protocol for all contacts on day 09 and day 10. Active search for additional cases in the community was undertaken. Active surveillance by the screening of contacts was done twice in a day for the development of any symptoms and signs of ILI and was followed up for a period of 28 days. Daily reporting was done from the Industrial warehouse by the medical officer in-charge, which enabled early detection and also strict adherence to COVID-19 safety precautions. Anyone developing any signs and symptoms of ILI were referred to the hospital for further management. Disinfection of the entire containment zone and buffer zone was carried out daily. Sodium hypochlorite was used for fumigation and wet mopping was carried out. Masks were worn by all individuals in the containment and buffer zone. Strict handwashing was ensured for all individuals. All were issued individual hand sanitizers. Daily health education was undertaken to ensure social distancing. Hygiene of washrooms was maintained by frequent disinfection and cleaning with Cresol black. Chemoprophylaxis with hydroxychloroquine as per extant guidelines was initiated for the 28 high-risk contacts. A control room was set up at the warehouse, which was in communication with the COVID-19 Surveillance Unit at Headquarters for collecting and collating data and reporting to the Integrated Disease Surveillance Programme.Results
On May 8, (taken as day 0), a suspect case of COVID-19, a 52 years old male employee from the warehouse was admitted to the nearest tertiary care COVID-19 hospital with a history of breathlessness for 04 days. He did not give any history of travel outside the base in the past 14 days. His primary duty was checking of entry of trucks, as a result of which had come in contact with various truck drivers who were bringing stores into the warehouse premises in the past 1 month. He was on duty between 12 and 10 days before he developed symptoms (D-12 and D-10), which is 6 to 8 days before the onset of symptoms, and hence, a possible primary case could be one of the drivers of the truck; however, no particular individual was identified. The suspect case tested positive on D + 3 and is the index case. Three individuals tested positive on day 03 and 06 respectively [Figure 2]. On daily ILI surveillance, symptomatic cases were referred to the COVID-19 hospital till day 10 and five of them were confirmed as positive, four of them had fever and two had complained of breathlessness. Testing by RT-PCR was carried out for all the primary contacts of the index case, and 15 males were found to be positive. Out of the secondary contacts tested 01 male and 01 female tested positive and were admitted [Figure 2].Figure 2: Day wise occurrence of cases of COVID-19 at industrial warehouse
There were 86 individuals from the warehouse belonging to two cohorts, and 52 individuals staying in the residential area (32 individuals were workers at the warehouse and some were staying with family). The index case was admitted on May 8. He had symptoms of breathlessness for 04 days. Another five symptomatic cases were admitted till May 17. A total of 23 workers and 02 family members were admitted.
The working men were staying in two cohorts, consisting of 02 dormitories accommodating 20 and 29 personnel, respectively. Besides that, there were 10 single occupancy rooms, 06 double occupancy rooms, and 05 triple occupancy rooms. Each floor had one toilet block with 3 washrooms [Figure 1].
The index case presented with breathlessness for 4 days. His disease progressed rapidly to cause B/L pneumonia and he succumbed to the illness within 04 days of admission. As per records, he did not have any known comorbidity. Another personnel from the same cohort, who was a close contact of the index case and was admitted with a history of fever for 1 day, developed Bilateral Pneumonia, severe acute respiratory distress syndrome (ARDS) and succumbed on day 10. He also did not have any known comorbidity.
All confirmed cases from the area occurred within 14 days from the onset of the index case. The transmission of the disease was propagated in nature as it occurred from person to person confined to the defined area. The SAR of the outbreak was found to be 17.51% and was calculated as the number of cases divided by the number of contacts.Discussion
COVID-19 is an airborne disease with high infectiousness, long incubation period, relatively low virulence, and asymptomatic and presymptomatic transmission. In our study, we found five symptomatic and 19 asymptomatic cases detected within a span of 14 days from the diagnosis of the index case. Current evidence suggests that transmission of COVID-19 occurs primarily between people through direct, indirect (through fomites contaminated surfaces/objects), or close contact with infected people through infected secretions such as saliva and respiratory secretions, or through their respiratory droplets, which are expelled when an infected person coughs, sneezes, talks, or sings. The infection can get transmitted through normal talking or breathing also. In our study, we found that the disease transmitted rapidly among the inmates of the two blocks and the residential area, suggesting that once COVID-19 has been introduced into a facility, it has the potential to spread rapidly and widely.
The most common symptom reported in our study was fever, followed by breathlessness. Similar results were also seen in studies in different settings where fever and cough were found to be the most common presenting symptom. However, two symptomatic personnel who were admitted deteriorated rapidly and developed bilateral pneumonia, ARDS and expired within a short period. ARDS has emerged as a complication in other studies also. Similar outcomes were observed in a study in China, where disproportionately higher mortality was seen among individuals >60 years. However, mortality due to COVID-19 has also been shown in 50–60 age group.
Studies have shown that COVID-19 transmission can occur in the early phase of the illness, when the patients are asymptomatic;, similar asymptomatic transmission was observed in our setting where we found 18/24 (75%) to be asymptomatic. F Zhou in their study in a hospital setting, interpreted that asymptomatic carriers are potential sources of infection outbreak and should be screened as soon as possible. In a living systematic review by DB Garcia, the overall proportion of individuals found from 79 studies, who were COVID-19 positive and remained asymptomatic throughout, was 20% (95% confidence interval 17–25).
Our study revealed a SAR of 17.51 which is much lesser than that of 70% found amongst members living in a cluster and this may be because of the rapid control actions undertaken by the RRT.
A study on an outbreak in South Korea shows that COVID-19 can be exceptionally contagious in crowded office settings such as a call center. The magnitude of the outbreak illustrates how a high-density work environment can become a high-risk site for the spread of COVID-19 and potentially a source of further transmission. One of the reasons that the same could be prevented in our setting could be due to active screening for ILI symptoms and prompt referral to hospital. Furthermore, the cohort system of not allowing people who were at high risk to interact with those at low risk for meals and even while using washrooms enabled stalling the spread. Studies have shown that COVID-19 infection can follow a downhill course where early contact tracing and isolation has been instituted. Detailed contact tracing and testing of contacts at high risk decreased the asymptomatic transmission in our study. Similar decrease was seen in a study by Aron et al. in 76 residents of a Nursing facility in Washington. Aerosolized transmission of disease presents a unique challenge in infectious disease control; further, it has been predicted that by reducing the human to human contact by 90%, we can contain the epidemic. Disinfection was done daily in our setting and the key role of surface cleaning in halting COVID-19 transmission and mitigating the COVID-19 pandemic has also been brought out by researchers in France.
The use of face masks by all was advocated. The residents within the containment zone, buffer zone and all personnel attending to them were to use masks. Consistency of individuals in handling personal protective equipment was ensured such as following of correct donning and doffing techniques and observation of strict hand hygiene.
Since the virus can remain viable and infectious in aerosols for hours and on surfaces up to days, emphasis was laid on daily disinfection with Sodium Hypochlorite along with wet mopping and wet dusting. Quarantine and Isolation were ensured and being a structured community, this discipline was easier to achieve.
From [Figure 2] and [Figure 3], it is observed that the infection had spread mainly due to close contact amongst the inmates within the same Cohort and between the Cohorts over a period of time. The disease did not follow a perfect epidemiologic curve as the asymptomatic positive cases were admitted to the hospital as and when they were tested positive. The study was a descriptive study of control of the highly infectious disease and data was analysed from the primary data available.Conclusion
Our findings suggest that owing to the high levels of COVID-19 transmission from asymptomatic and presymptomatic individuals, contact tracing, testing, and isolating the cases would be the most effective control measure to break the chain of person-to-person transmission in the same cohorts and in interdependent cohorts in the same defined area. The benefits of the contact tracing strategy also depend on adherence of the early quarantining of the individuals who have been traced. Known prevention and control measures like decongestion of crowded living areas along with staggered meal timings to reduce physical distancing along with the use of facemasks and hand hygiene, when applied, rapidly aid in limiting the spread of a highly infectious airborne virus from a defined area. The lessons learnt from this epidemiological study on COVID-19 can be extrapolated to formulate effective working guidelines best suited to such settings.
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Conflicts of interest
There are no conflicts of interest.