Contact tracing, quarantine and isolation
Contact tracing is best undertaken when the number of cases is very low, because the number of contacts increase exponentially with every case. It is important to remember that contact tracing is a resource intensive activity- the European Centre for Disease Prevention and Control estimates that it would take 100 person-hours of work to trace the contacts of a single COVID-19 case (this number may be accurate in Europe, but not in Asia or Africa, where population density is much higher). Moreover, contact tracing is a useful activity only when it is possible to trace at least 70% of contacts (estimates vary from 70% to 90%). In settings with high population density and population mobility, one is unlikely to achieve such standards. In addition, a substantial proportion of infected are asymptomatic and capable to transmitting infection to others. While the overall prevalence of asymptomatic cases is reported to be 16% (based on a systematic review), it could be as high as 80%. Even if all symptomatic cases were identified, and optimum contact tracing was performed for them, the presence of large numbers of asymptomatic cases reduces the effectiveness of contact tracing as a tool for containment. Further, concealment of contact history to avoid quarantine/isolation is common.
In order to identify asymptomatic cases, large-scale testing would be required. However, the cost of such an exercise would be prohibitive in resource-limited settings. One option in such settings would be pooled testing instead of individual testing. However, pooled testing is appropriate in specific situations only.
Quarantine and isolation are the logical actions following contact tracing. This could be self-quarantine, home or hospital quarantine/isolation. Regardless of the setting, persons in quarantine are expected to limit contact with others, maintain physical distance, use masks, etc. Due to the disruption posed by quarantine/isolation, many resist the same. Enforcement of these measures then requires the involvement of law enforcement agencies after invoking appropriate legislation (provided such legislation exists). Even so, there are several instances of individuals breaking quarantine/ running away from quarantine centres. In a democratic country, strict enforcement of containment measures is often problematic.