In a fascinating pre-print article in medRxiv, entitled Long, thin transmission chains of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2) may go undetected for several weeks at low to moderate reproductive numbers: Implications for containment and elimination by Gerry F. Killeen, he raises some interesting points about contact tracing and issues associated with asymptomatics, larger clusters versus long thin chains and the ability to use contact tracing to identify and limit the propagation of the virus.
If you think about a situation in which an asymptomatic person is infecting others, who may themselves be asymptomatic, but not in large outbreak clusters; these “long thin chains” essentially could go on for a few generations before identification. We typically use contact tracing to identify these clusters and seek to mitigate their impact via the process of:
A symptomatic person is identified and then one contact traces back all significant contacts during the prior 48 hours as per the 6/15/48 rule (within 6 feet for at least 15 minutes during the prior 48 hours before symptoms appeared or a positive test).
What this means for us as discussed in this article and some thoughts:
- We need to recognize these types of chains and factor them into our thinking
- Contact tracing in and of itself based upon our current methodology will not be enough to fully stop the spread. Trying to contact trace back a month or so is note feasible, nor could you expect to identify all close contacts.
- We need to continue to provide our effective mitigation strategies (wear a mask, social distancing, wash hands, no large events, etc.) for longer periods than one would expect as these transmission chains take longer to identify and mitigate
- Rapid, inexpensive point of care testing on a daily/frequent basis could help to expose these chains and those infected
- Particularly in the younger populations, we need to actively seek out those infected via other means
