Successful contact tracing and the purpose of lockdowns

Sri Lanka's has experienced a spike in Covid-19 detections since early October and the authorities have responded with a series of localised curfews, shutting down parts of the country, mostly in the Western province. While the centre of the city is now open some suburbs (eg Dematagoda, Borella) have been under curfew for about three weeks while parts of the Western province (eg Negombo) have been under curfew for a month, if not longer.

A lockdown suppresses the disease for a while and slows its spread. While it does not eliminate the disease it buys time while measures to increase public health care capacity (procuring emergency hospital space, breathing ventilators, medical protective equipment, and testing kits) are put in place. It also allows contact tracing to take place.  

"if you can find infected cases, isolate and treat them, and trace the close contacts who they might have infected, and isolate them too, then you can keep much of the infection out of the general population."

This of course is most effective when the caseload is low, if the number of cases is high then the number of contacts to trace multiples which means many more contact tracers have to be employed and much more tests need to be done. Sri Lanka's strategy has been largely about tracing and isolating contacts which has been done with the assistance of the military intelligence and other service units.  

If all contacts are traced and properly isolated then the spread can be slowed or even perhaps stopped completely but this requires specialised skills. 

"Case investigation and contact tracing is a specialized skill. To be done effectively, it requires people with the training, supervision, and access to social and medical support for patients and contacts. Requisite knowledge and skills for case investigators and contact tracers include, but are not limited to:

• An understanding of patient confidentiality, including the ability to conduct interviews without violating confidentiality (e.g., to those who might overhear their conversations)
• Understanding of the medical terms and principles of exposure, infection, infectious period, potentially infectious interactions, symptoms of disease, pre-symptomatic and asymptomatic infection
• Excellent and sensitive interpersonal, cultural sensitivity, and interviewing skills such that they can build and maintain trust with patients and contacts
• Basic skills of crisis counseling, and the ability to confidently refer patients and contacts for further care if needed
• Resourcefulness in locating patients and contacts who may be difficult to reach or reluctant to engage in conversation
• Understanding of when to refer individuals or situations to medical, social, or supervisory resources
• Cultural competency appropriate to the local community"

Public trust is essential for contact tracing to work. People need to volunteer information so that potential cases can be tested and their contacts traced. If people are fearful then they are less likely to visit hospitals or volunteer information. There are a number of reasons why I believe this is low.

First, the worry uppermost in people's mind is that they will be shipped off to harsh quarantine centres with little in the way of facilities. The authorities have supposedly said that people can now isolate at home instead of being sent to a centre but given the lack of consistency in policy how many will believe this?

Second, the sensationalist approach by the media that portrayed this like a cricket match; daily scores of  infections and deaths accompanied by gleeful comparisons with other countries to show that we were 'winning the match'. The public bought into this and seem quite obsessed with the whole issue. 

Third, this approach leads to an 'us' v 'them', mentality, the disease is the enemy and the campaign as a war. This meant that victims became the enemy and were stigmatised. The guide emphasises how patient confidentiality needs to be maintained:

"to protect patient privacy, contacts are only informed that they may have been exposed to a patient with the infection. They are not told the identity of the patient who may have exposed them."

It is the medical professionals who should do the contacting, not the potential patient. In Sri Lanka the authorities paste posters on people's houses warning the public of potential infection which creates stigma while the public helpfully circulates lists of potential contacts leaked from various sources or concocted from somewhere.

Given this environment how many will seek treatment in a hospital for a cough or a sniffle? How many will voluntarily provide information on all their contacts? They may delay treatment until acute symptoms set in.

Undoubtedly the military intelligence are well experienced in extracting information from people but can they get all the information needed? 

The authorities are cremating the bodies of victims but Muslims say this practice is against their religious beliefs. Will this dissuade them from seeking treatment or divulging information? 

For successful contact tracing what percentage of the contacts need to be successfully identified and isolated? I don't have an answer but it is a complex task.

"Another consideration is whether the system identifies most – if not all – contacts an infected person has had during their infectious period. People may not recall (or choose not to reveal) their contacts. It is also not straightforward working out who has had significant contact. The current definition assumes “significant” to mean close proximity (less than 2 metres) and prolonged contact (more than 15 minutes). These are arbitrary thresholds.

Contact tracing is also laborious and time consuming. A study of contact tracers in Sheffield reported that each interview with an infected person to identify their contacts took around 80 minutes. The average number of significant contacts identified for each person infected with COVID-19 – around 30 contacts per case – was also high. Consequently, the workload involved is significant."

The logistics of this become well-nigh impossible if the caseload is large. In sum, even with extensive curfews, the process of contact tracing may fail to identify sufficient numbers of potential victims which means the curfew can only provide a temporary suppression in transmission.

There will be increases in the number of cases following the easing of curfew but the response should be calibrated within the framework of containment, not resorting to repeated curfews. Norman Loayza of the World Bank  warns that:

“Worse than a lockdown is a series of repeated and uncertain lockdowns. The risk of second and third waves of infection is large in populations with low immunity. The prospect of repeated and uncertain lockdowns can devastate the economy and worsen human suffering beyond comprehension.”