How the COVID-19 Supply Chain Succeeds When It Fails

Supply chains triumph when they complete deliveries satisfactorily — but not when the payload is the COVID-19 virus.

Framing the fight against the pandemic in supply chain terms makes it clear that to stop the spread of the virus, we must ensure that its supply chain fails. We can secure failure by using disruptors to prevent deliveries of the supply chain’s deadly freight. But not disruptors such as adverse weather that derail product supply chains. These are special disruptors that include masks, quarantines, and social distancing.

Various conveyances to choose from

Our point of origin for the COVID-19 supply chain is an infected individual. He or she has an “inventory” of virus payloads waiting to be transported to multiple destinations — uninfected people. The payloads are packaged in droplets of moisture that are dispatched by the person’s breath.

We can segment this inventory into small and large droplets. Large ones exceed five microns in size, and when dispatched, fall harmlessly to the ground within about two meters or six feet of the point of origin (the infected person). However, smaller droplets measuring less than five microns stay aloft in the form of aerosols and travel beyond the two-meter mark. This is the freight we need to prevent from being delivered to virus-free people.

The coronavirus has several modes of transportation at its disposal for conveying small droplets. The tiny droplets contain virions (the infective form of the virus) and are dispatched in different shipment sizes by an infected host depending on the transportation mode. Here are some examples.

• A host sitting quietly dispatches approximately 20 virions per minute.
• A talking host dispatches approximately 200 virions per minute.
• A host who is singing, shouting, or exercising dispatches approximately 2,000 virions per minute.
• A sneezing host dispatches approximately 200,000,000 virions per sneeze.

Clearly, sneezing is the most effective mode of delivery.

Lowering the performance bar

We can lower the likelihood of successful deliveries by deploying disruptors. The ultimate disruptor is a vaccine, which brings the COVID-19 supply chain to a halt by refusing delivery of the freight. Hopefully, we will have a vaccine soon; meanwhile, here are some alternative disruptors.

Social distancing. Since large coronavirus packages only have a range of a couple of meters or so, positioning points of delivery beyond this range lessens the chances of spreading the virus. Smaller packages travel further, but if uninfected individuals keep their distance, there is less chance they will receive a delivery of the coronavirus.

Masks. An effective way to disrupt the COVID-19 supply chain is to prevent packages from moving beyond the inventory stage. Masks provide such a barrier, but their effectiveness depends on how they are constructed. Dense-weave cotton offers a formidable barrier; silk is even better. A combination of the two is almost certain to disrupt COVID-19’s delivery schedule. The top-performing disruptor in this category is the N95 mask.

Track and trace. Supply chain track and trace, or contact tracing and testing in pandemic parlance, can be a powerful disruptor. We track the coronavirus’s path, pinpoint where it is inventoried, and temporarily close that distribution center. However, this option is subject to logistics challenges, such as how many tests and test nodes are available and where they are located. The more testing, the more effective is the track and trace disruptor.

Quarantine or isolation. Having identified the locations of coronavirus inventories, (i.e., infected people), we can isolate them and cease all shipments. A supply chain without shipments is impotent.

A measure of failure

The adage that you can’t manage what you can’t measure applies to the COVID-19 supply chain. But how can we measure the performance of a virus supply chain?

A critically important metric is “R naught” (Rօ), an indicator of an infectious agent’s transmissibility. In simple terms, an Rօ of 1 means that an infected person will infect one other individual who will infect one more person. If the metric’s value is two, an infected person will pass on the virus to two others and so on.

If Rօ has a value of less than 1 an outbreak will cease; if Rօ is greater than one the outbreak will grow.

Just as various types of disruptions undermine product supply chains, different combinations of disruptors can lower the performance of the COVID-19 supply chain and hence reduce its Rօ value. For example, testing twice per week can reduce Rօ but not as much as certain combinations of mask-wearing and contact tracing.

Upside down

Striving to hobble the performance of a supply chain may go against the grain, but that is how we can overcome this pandemic. Besides, COVID-19 has already turned our world on its head.

This blog post draws on the work of the MIT Institute for Data, Systems, and Society (IDSS), and a recent presentation delivered by Professor Anette (“Peko”) Hosoi, Associate Dean of Engineering, Neil and Jane Pappalardo Professor, Mechanical Engineering, MIT. For more information on the IDSS research and COVID-19 response mechanisms, please visit the IDSS COVID-19 Collaboration web site. Thanks to Professor Hosoi for her help with this article.