CONTACT tracing is an old-school epidemiological tool used for breaking the chains of transmission of infectious diseases during an outbreak. This approach is recommended to identify, educate, and monitor individuals who came in close contact with someone infected with a pathogenic microorganism. According to the Centre for Disease Control, a close contact is defined as any individual who remained within six feet of a person infected with an infectious disease, such as COVID-19, for at least 15 minutes within two days before positive specimen collection or confirmed symptoms. The World Health Organisation recommended a comprehensive strategy of case identification, isolation, testing and care, contact tracing and quarantine as critical activities to control the devastation of COVID-19. Bangladesh and many other countries are facing significant challenges to mobilise resources for adequate test facilities, quality hospital care, isolation and quarantine activities, where contact tracing broadly remains as an unexplored priority.
Like other public health interventions, contact tracing is also a systematic approach. The Centre for Disease Control guidelines recommended specific steps for contact tracing to be effective.
Step 1: Responsible national health department should establish coordination with networking laboratory facilities to collect SARS-CoV-2 test positive results along necessary demographic and other information of the cases.
Step 2: Rapid notification within 24 hours of SARS-CoV-2 test results or diagnosis of respective cases along with necessary instructions for self-isolation and precaution. Communication with the cases could be made through different channels such as phone, text, email, or in-person (least priority and with all precautions) maintaining confidentiality of information.
Step 3: The interview of the cases by telephone or video-conference instead of in-person to collect information on risk assessment, socio-demographic information of the cases and their potential contacts. Digital tracking of the potential contacts of primary cases may be ascertained at this stage.
Step 4: Primary case and close contacts diagnosed with COVID-19 to be monitored daily on their temperature and COVID-19 symptoms throughout the length of their self-isolation period.
Step 5: Additional follow-up may be needed for clients with COVID-19 who have underlying health conditions and people in long-term care facilities.
Step 6: Second test and additional medical consultation to make further decision to release from self isolation or quarantine. Contacts who remain asymptomatic for 14 days after last exposure can be notified of their release from monitoring and provided general health education.
For countries with inadequate health care capacity, the Centre for Disease Control recommended a hierarchy for prioritisation of contract tracing activities.
Priority 1: Contact tracing should target hospitalised patients, health care personnel, first responders (law enforcement, firefighters), individuals living or working at long-term care facilities and individuals living or working congregate settings etc.
Priority 2: Special attention should be given to individuals aged 65 years and above, individuals with pre-existing health condition, eg, diabetes, chronic asthma, hypertension, cancer etc and pregnant women.
Priority 3: Individuals who show COVID-19 symptoms but do not meet any of the above categories come next in the hierarchy.
Priority 4: Individuals who do not show symptoms and do not meet any of the above categories are the last in the hierarchy.
South Korea was one the countries that started rigorous contact tracing at an early stage of the COVID-19 pandemic and the country has been successful in containing the spread of the virus. South Korea and a few other countries implemented a mix of traditional and digital contact tracing approaches, where they verified each positive case with data from medical records, closed-circuit television cameras, cell phone geolocation data and financial transactions, to create a detailed record of an infected individual’s past movements. Detailed information about each infected individual’s previous movements was then sent by text message to the individuals who have been nearby.
To supplement the traditional contract tracing method, there have been numerous initiatives of digital contact tracing using computer or mobile phone-based apps. To minimise delays between case identification and contact notification, apps can be used to assess distance and duration thresholds to define exposure between a case and the potential contacts. Notifications could then be rapidly and automatically sent to potential contacts, recommending isolation until further follow-up with more specific traditional contact tracing.
Google and Apple have collaborated to create application programming interfaces (APIs) to provide a cross-platform for public health agencies for contact tracing. Bangladesh has rolled out a contact tracing app on a trial basis to warn users if they have been near someone who later tested COVID-19 positive. The Corona Tracer BD has been developed by local technology company in collaboration with the government.
The adoption of digital contact tracing is not easy as it brings challenges at various levels. Many of these apps use bluetooth technology, putting aside how many devices carry this technology, there are other issues about how it deals with older people and people with special needs, privacy and confidentiality of the cases and their contacts. Another challenge in contact tracing in case of COVID-19 is that the disease can be transmitted by people who are infected but asymptomatic and by those who are infected but have not yet developed symptoms (pre-symptomatic transmission). Pre-symptomatic cases are manageable with a contact-tracing programme because their status will more likely to be known, while asymptomatic cases will be a missed opportunity with the understanding that symptomatic cases are the major source of transmission than asymptomatic carriers.
Contact tracing could be a cost-effective alternative to blanket area-wise lockdown where it is possible to isolate potentially infected people rather than the whole community. Lockdowns are necessary during the early stage of an outbreak to allow time for preparation in terms of strengthening capacity of testing facilities, hospital care, planning of health care personnel, and other essential resources. In Bangladesh, contact tracing is implemented centrally by the Institute of Epidemiology, Disease Control and Research, which appears to suffer from limited resources, inadequate monitoring and a clear policy guideline. A structured contact tracing programme in Bangladesh is needed under an expert guidance with involvement of primary health care workers and trained volunteers dedicated to COVID-19 to maximise its coverage and effectiveness.
Dr Nazmul Alam is an associate professor of public health at Asian University for Women. He worked as an associate scientist at the ICDDR,B.
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