Authors: Dr. Jean-Paul Rodrigue, Dr. Thomas Luke (Department of Virology, Naval Medical Research Center) and Dr. Michael Osterholm (Director of the Center for Infectious Disease Research and Policy (CIDRAP), University of Minnesota)

Transportation systems due to their speed and ubiquity act as a vector in the diffusion of pandemics.

1. Pandemics

There are approximately 1,500 microbes that are known to be a source of disease among the human population. Influenza is a virulent disease because of its ability to mutate and be efficiently transmitted through the respiratory route. Under normal circumstances, influenza’s impacts are relatively benign since populations have developed a level of immunity to its debilitating effects. Yet, it is estimated that between 1 to 1.5 million people per year die of influenza or related complications with a distinct seasonality that runs between October and March in the northern hemisphere and between May and September in the southern hemisphere. Influenza pandemics are thus considered among the most significant threats to the welfare of the global population.

Pandemic. An epidemic of infectious disease that spreads through human populations across a large area, even worldwide.

Over the last 300 years, ten major influenza pandemics have occurred. The 1918 pandemic (Spanish Flu) is considered the most severe. 30% of the world’s population became ill, and 50 and 100 million died. One important reason the Spanish Flu spread quickly and extensively was through modern transportation, which offered global coverage at the beginning of the 20th century. The virus was spread around the world by infected crews and passengers of ships and trains, and severe epidemics occurred in shipyards and railway personnel.

In a contemporary setting, there are a variety of factors that can promote the spread of diseases, such as ubiquitous air travel. Concerns about the emergence of a new pandemic are salient, particularly in light of recent outbreaks such as SARS (Severe Acute Respiratory Syndrome) in 2002-2003, the Avian Flin in 2005, the Swine Flu in 2009, and the coronavirus in 2019-2020 (COVID-19) which quickly spread because of the convenience and ubiquity of global air travel. Pandemics, such as the Spanish Flu and COVID-19, have shown that widespread illness or absenteeism in freight transportation sectors can cause cascading disruptions of social and economic systems. The relationships between transportation and pandemics involve two major sequential dimensions:

• Transportation as a vector. With ubiquitous and fast transportation comes a quick and extensive diffusion of communicable diseases. From an epidemiological perspective, transportation can thus be considered a vector, particularly for passenger transportation systems. The configuration of air transportation networks shapes the diffusion of pandemics. The global air transport system is composed of airports with different volumes and connectivity, implying that depending on the airport, there is a potentially different scale and scope of diffusion. This issue concerns the early phases of a pandemic (first ten days), where transportation systems are likely to spread any outbreak at the global level.
• Continuity of freight distribution. Once a pandemic occurs or immediately thereafter, the major concerns shift to freight distribution. Modern economic activities cannot be sustained without continuous deliveries of food, fuel, electricity, and other resources. However, few events can be more disruptive than a pandemic, as critical supply chains can essentially shut down. Disruptions in the continuity of distribution are potentially much more damaging than the pandemic itself.

2. Vectors and Velocities

The more efficient transportation, the more efficiently the vector can transmit infectious diseases. International and long-distance transport, such as air and rail, modes and terminals alike, concentrates passengers and increases the risk of exposure. In the past, this could be an advantage as a ship could be quarantined since there was ample time during the voyage for an infection to carry its course and the symptoms to become apparent. In a contemporary setting, the velocity conferred by transportation systems for long-distance travel is superior to the incubation time of many flu variants (the period after the infection before symptoms are revealed). On the positive side, the fact that transportation quickly spreads diseases enables global populations to develop immunity to a wide array of less virulent diseases, which may improve their overall immunity to more virulent diseases. This cross-immunity may contribute in the future to the mitigation of severe pandemics.

Since the incubation time for the average influenza virus is between 2 to 7 days, and 3 to 10 days for COVID-19, there is ample time for someone infected to travel to the other side of the world before noticing symptoms. This represents the translocation phase, which is the most crucial in a pandemic. Thus, in a window of a few days before an outbreak could become apparent to global health authorities, a virus could have easily been translocated to many different locations around the world. At this point, the vector and velocity of modern transport systems would ensure that an epidemic becomes a pandemic, as was the case for COVID-19. On occasion, the velocity of global transportation systems is higher than at the regional level, which paradoxically implies that a virus can spread faster globally – between major gateways – than at the regional level.

Once an outbreak becomes apparent, the global passenger transportation system, such as air travel and passenger rail, can quickly be shut down in whole or in part, either voluntarily (more likely if the outbreak is judged to be serious) or by the unwillingness of passengers to be exposed to risks. Although travel restrictions may not prevent the total number of infected individuals, they slow down the rate of spread and give more opportunities for actors such as public health agencies, corporations, and individuals to prepare and implement mitigation strategies. The latter happened during the SARS outbreak in 2003 and the coronavirus (COVID-19) in 2020. While the public transportation systems of several large Chinese cities were still operational, the number of users precipitously dropped because of risk avoidance. The SARS outbreak also had a substantial impact on the global airline industry. Cities with direct flights to Hong Kong were 25 times more likely to record a SARS case than cities that were not directly connected. Cities requiring two or more connecting flights to reach Hong Kong did not record a single case. After the disease hit, flights in Pacific Asia decreased by 45% compared to the previous year. During the outbreak, the number of flights between Hong Kong and the United States fell by 69%.

In early 2020, the coronavirus (COVID-19) pandemic underlined the impacts of China’s high connectivity in the diffusion of the disease, particularly for the following reasons:

• The epidemic took place during the Chinese New Year, representing the peak period of passenger mobility within China. In 2019, about 415 million people traveled for the occasion.
• The growth of domestic air travel and the setting of China’s high-speed rail network have supported substantial growth in national passenger mobility. In 2019, the Chinese air transport network handled more than 659 million passengers, up from 266 million in 2009.
• The number of Chinese citizens traveling abroad for tourism and business purposes has surged. The airports of several large Chinese cities offer direct services to a number of destinations across the world. In 2019, there were 166 million outbound Chinese tourists.
• China became the world’s second-largest cruise source market, with 2.4 million passengers in 2018.

During the COVID-19 pandemic, cities such as Wuhan (the emergence point) were quarantined, and a large part of the civilian air network was shut down. International airlines canceled their services to almost all Chinese cities. As the pandemic spread to Europe and the Middle East, air services were curtailed because of a significant drop in demand, cancelations, and no-shows. Later, the United States shut down flights with most European countries in an attempt to curtail the spread of the pandemic. By April 2020, air passenger activity declined by a factor of 90 to 95% in most air markets in Europe and North America. The last time an event of that scale happened was in 2010, when European and transatlantic air travel was forced to shut down because of an Icelandic volcanic eruption. Any economic activity involving social interaction was seriously curtailed. This was particularly the case for the tourism industry, with the cruising industry completely ceasing operations for the remainder of 2020.

3. Continuity of Freight Distribution

However dramatic the impacts of modern transportation as a high-velocity vector for a pandemic, a potentially greater risk resides in the geographical and functional structure of supply chains because the continuity of freight distribution could be compromised. Up to the mid-20th century, the scale of production, transport, and retail was dominantly local (food) or regional (durable goods such as cars). Since then, globalization has substantially expanded the scale at which a wide array of goods is distributed, such as minerals, energy, grains, parts, and finished goods. Thus, the interconnectedness of the global economy, while being a net advantage from a supply chain standpoint, could make an influenza pandemic more devastating than the ones before it. Even the slightest disruption in the availability of parts, finished goods, workers, electricity, water, and petroleum could halt many aspects of contemporary life.

The global economy has been favored by exploiting comparative advantages and tight management of supply chains. Inventories are kept to a minimum through strategies such as just-in-time. Virtually no production surge capacity exists. As a consequence, most markets depend on the timely delivery of many critical products (such as pharmaceuticals, medical supplies, food, and equipment parts) and services (such as communications support). Contemporary supply chains are complex and interconnected and can be subject to shocks and disruptions. Only the actors organizing and managing them have a true perspective about their scale, scope, and vulnerability. However, this perspective is limited to specific supply chains as actors involved in food distribution differ from those involved in pharmaceuticals or energy. It is consequently difficult to assess the impacts of a pandemic on supply chains because of the variety of actors, locations, modes, terminals, and distribution centers involved in each.

Supply chains are also specialized and fragmented, implying that if the demand changes in one sector, other related sectors are not necessarily able to adjust. This is particularly the case between commercial and consumer demand. For instance, food supply chains are usually divided between groceries, institutional, and restaurant providers. If a large share of the population does not work and commute during a quarantine, commercial demand will drop while consumer demand will rise. Supply chains may not be able to respond to the switch in the demand pattern, even if the aggregate demand remains similar. Shifting supply chain channels requires new interactions between actors. Further, the origins, destinations, modes of transportation, and even the packaging and shipping of the cargo have to be modified. Consequently, pandemics impact supply chains over two dimensions:

• Supply shocks. An unexpected sudden change in the availability of raw materials, parts, goods, and manufacturing capabilities. It is usually accompanied by price surges, but the availability of essential components can be undermined because of a lack of raw materials, parts, or the lack of labor necessary for their procurement. Depending on the existing buffer, such as stockpiles of energy, grain, or raw materials, the supply shock can take some time to propagate.
• Demand shocks. Demand shocks imply a sudden change in demand due to unforeseen circumstances. For items such as food, hoarding may trigger a temporary surge in demand, with several items becoming unavailable. In other sectors, such as energy, the demand may drop substantially because of declines in commuting and travel. Demand shocks back-propagate along the supply chain, impacting distributors, manufacturers, and suppliers.

The transportation industry has consolidated into a small number of global and national mega-players to achieve massive economies of scale. This is the case for the two most important global freight transportation modes; maritime shipping and air cargo. Since the frequency, speed, and reliability of shipments are high under normal circumstances, manufacturers have relocated their facilities to lower-cost locations. Because transportation costs are lower than inventory management costs, retailers and secondary manufacturers employ just-in-time inventory systems – their stockpile flows in the transportation stream as inventory in transit. Most supply chains are re-stocked continuously, on par with the demand labeled pull logistics. Typically, air cargo shipments such as pharmaceuticals and electronics are shipped directly from the place of production to markets in a matter of hours. Maritime shipments can take two to three weeks to reach their destinations on transoceanic routes.

The typical efficiency, and potential non-resiliency, of critical supply chains, as a function of transportation would be placed under stress during a pandemic. The most important include:

a. Food

Contemporary food production and distribution rely on low inventory levels to avoid waste of perishable products on store shelves. On average, supermarkets have between 2 and 5 days of inventory of perishable goods (dairy, produce, meat) and about 1 to 2 weeks for other goods (pasta, canned goods, etc.). It is worth underlining that these figures are for a normal and stable demand. In the case of a pandemic, available food supplies could quickly be exhausted through hoarding behavior and a shift in consumption patterns. The main driver for hoarding is the fear that essential items will not be readily available in the future. Such behavior is commonly observed during an acute weather event such as a hurricane, where store shelves of essential goods and supplies are quickly emptied.

The main difference with a pandemic is that instead of a local or regional surge in hoarding, the process takes place at the national level, placing intense pressure on food distribution. Hoarding stresses supply chains by moving the inventory from stores and distribution centers to residences. Further, during an acute weather event, the fear is that the supply system, including public utilities, will be damaged, physically delaying replenishment. This is not the case during a pandemic, as all physical infrastructure remains intact, making hoarding behavior unwarranted. Replenishing inventory may take time, particularly if a pandemic impacts production and distribution systems.

On the positive side, hoarding lessens future demand as people consume items they have hoarded and will impose limited demand on stressed distribution systems. However, food hoarding may remove supply from those who need it at a critical time or for those who decide not to change their consumption. The closing of restaurants may also shift additional demand towards grocers, particularly in advanced economies where a large share of food expenses are for eating out. The food production and distribution capabilities of restaurants and caterers must remain available during a pandemic. Therefore, food security is defined by the ability of transportation workers to move food from producers to bulk-storage facilities, processors, and grocers.

b. Energy

The provision and distribution of energy are critical to the functioning of a modern economy and society. For instance, about 40% of the world’s electricity supply is generated by burning coal. In the United States, this share was 50% until the mid-2000s but fell to 35% recently due to a higher reliance on natural gas. Coal power plants maintain a fairly low stockpile, about 30 days, and rely on a constant supply from major coal mining regions, which tend to be far away.

While a pandemic does not directly damage energy systems, many energy distribution systems can be threatened by removing essential personnel from the workplace for weeks or months and impaired transportation capabilities to supply power plants. On the positive side, a pandemic should be associated with a substantial drop in energy demand as institutional and manufacturing activities are curtailed, as commuting is reduced, and as international transportation such as air travel and maritime shipping decline. As observed in the early stages of the COVID-19 pandemic, the outcome is a sharp drop in energy prices due to the lack of demand.

c. Medical supplies

A pandemic is associated with a surge in medical facilities, equipment, and pharmaceutical products. It is likely to be the only sector where a surge in demand is expected to endure once hoarding has subsumed. Global drug production is controlled by a few large conglomerates that maintain a limited number of facilities at selected locations. Commonly, a single drug is produced at a single plant. If global distribution systems were impaired during a pandemic, many essential drugs would have difficulties reaching patients, while limited stockpiles maintained at medical facilities would quickly run out.

For instance, over 95% of all generic drugs used in the United States are made offshore, primarily in China and India. A similar pattern applies to critical medical equipment such as ventilators. Even simple respiratory masks could quickly run out. In 2017, Hurricane Maria hit Puerto Rico, substantially damaging infrastructures, particularly the power generation system. In the aftermath, a shortage of saline solutions was felt because Puerto Rico was a major supplier of these solutions to hospitals across the Americas. During the COVID-19 pandemic, personal protective equipment, particularly masks, became a salient issue since it suddenly shifted from a specialized market geared towards the medical industry to a mass-market consumer good.

The COVID-19 pandemic was a stress on available food, energy, and medical resources, which faced shortages and scarcity, but remained functional. Thus, supply chain issues, if not properly mitigated, are expected to compound the impacts of a pandemic seriously.

4. Possible Mitigation Strategies

Since pandemics have been an enduring concern with frequent risk reminders, many government agencies have developed pandemic plans. Paradoxically, there is no lack of pandemic plans but an oversupply of such schemes. The outcome has been confusion about responsibilities and strategies, as plans tend to be duplicative. Further, many pandemic preparation plans fail to account for the importance and ramifications of global supply chains. They are essentially designed with the assumption that national economies are mostly self-reliant. The geographic and functional realities of the global economy are quite different from this assumption, and the COVID-19 pandemic clearly underlined the importance and vulnerability of global supply chains. Cascading disruptions in vulnerable freight transportation systems and strategic supply chains can compound the difficulties of maintaining social cohesion and critical infrastructures during a pandemic.

Transportation systems, due to their nature and operations, are facing radically different impacts and mitigation strategies:

• Transit systems. These systems are essential for workers and personnel to commute to their functions to support economic activities and critical services. Because of the high density of passengers carried in close proximity and often in direct contact, such as on trains, subways, buses, and transit stations, transit systems represent a high contamination risk. While the option is to shut transit systems down to reduce the risks of contagion, key transit infrastructure should remain operational during a pandemic, particularly if the system is automated or the operators are separated from the passengers. Service frequency should be reduced, and passengers should be informed that while the transit system remains operational, using such a system represents a risk and that precautions such as masks and social distancing should be taken. Since commuting demand drops substantially, passenger density in public transit systems would decline proportionally.
• Road and highways. Individual mobility represents a safe form of transportation during a pandemic, as individual car and truck drivers have a very low level of contamination exposure while operating their vehicles. This allows for the continuity of essential commuting and freight deliveries to distribution centers, retail outlets, institutions such as hospitals and elderly care facilities, and home deliveries. The main risks are during refueling, loading, and unloading, but these risks can be reasonably mitigated. Individual passenger and freight mobility should not be excessively restricted during a pandemic, with the mobility of trucks becoming a priority. Retaining home delivery capabilities through e-commerce is particularly important as it allows people access to essential supplies while minimizing contamination risks, particularly for the most susceptible. Over this matter, the Covid-19 pandemic was associated with a surge in e-commerce and related home deliveries.
• Air travel. The demand for air travel declines dramatically during a pandemic as travel restrictions are implemented, events such as conferences and sports competitions are canceled, and tourists are unwilling to travel, even to areas that may be unaffected. Many midsized airports risk losing their air connectivity and the associated cargo services entirely. A pandemic has the indirect advantage of freeing substantial airlift capabilities that can be used to carry large quantities of essential cargo using passenger aircraft. Therefore, airlines and key airports must maintain air travel capabilities with a pool of available aircraft, pilots, controllers, and ground personnel. Travel restrictions should, therefore, focus on passengers and allow airlines to continue offering services. The drop in air traffic may incite airports to rationalize their operations by closing terminals (or sections of terminals) and concentrating activities such as customs and security.
• Maritime shipping. The demand for maritime transportation declines at the onset of a pandemic, but at a lesser rate than air travel. The shift in demand patterns, such as lower consumption of discretionary goods, has a deflationary effect on container shipping. The demand for raw materials and energy declines as well, impacting bulk shipping. Ports may face a rationalization by shutting down some terminals and concentrating activities at terminals that are the safest and most efficient (e.g. automated terminals). The international maritime domain presents unique challenges as it plays a fundamental role in supporting the global distribution of essential commodities (food and energy), parts, and finished goods. The naval services of nations should prepare to establish task forces in international waters to quickly provide vaccines/antivirals and other health assistance to the multinational mariners of commercial vessels as they transit into or out of maritime chokepoints and sea lanes. International military and civilian entities can provide the organizational framework to protect global maritime commerce. Since cargo ship crews may stay onboard for several months as part of their rotation, suitable ports must be found to allow crew exchanges, including their repatriation.

For freight transport systems, this may involve prioritizing lanes for cargoes of crucial importance, such as food, medicine, medical equipment, or any goods in critical shortage. To support such operations, transportation workers must receive a high priority for support, including vaccines, prophylactic antivirals, and access to personal protective equipment. Pandemic planners must cooperatively develop plans and obtain the agreements and resources necessary to conduct health assurance campaigns at major transportation chokepoints and corridors. Transportation workers must also have a well-enunciated priority for healthcare services if they become ill during work travels. This requires that some national, state, and local health resources and response activities are reprioritized from traditional priority groups (elderly, etc.) to ensure that all citizens have a reliably adequate supply of essential supplies and services.

Using modern communication systems, national, state, and local licensing and regulatory authorities, industry, and unions can identify, locate, educate, and train the transportation workforce. Governments and transportation stakeholders (industry, unions, and workers) must create a cooperative plan identifying roles, resources, and responsibilities. This leads to considering logistics strongholds that include ports, airports, and logistics zones. These key infrastructures and their surrounding areas must be secured to ensure the continuous supply of essential goods so that basic economic functions, namely supplying energy, food, and medical services, can be maintained. The characteristics of each supply chain must be addressed independently as each may be impacted differently, such as for the stages of production, manufacturing, and distribution.

Because transportation workers must cross international and local borders, national and local entities, industry and unions, health agencies, and other stakeholders must provide this support without regard to their nationality or state of origin.

5. Post-Pandemic Recovery

Pandemics and sanitary concerns, particularly the recent COVID-19 event, underline that the level of disruption over transport systems is a function of the level of involved human interaction. Passenger transportation was more impacted than freight, particularly since a share of passenger movements is discretionary and can be subject to substitution. The pandemic underlined the crucial importance of e-commerce, which experienced remarkable growth due to substitution effects from conventional retail, as passenger transport systems, particularly tourism, cratered, freight distribution endured.

Once a pandemic is receding, the main concern shifts towards resuming economic and transport activities. Since a pandemic does not diffuse uniformly in space and in time, the sequencing of the recovery is also not uniform and reflects a prioritization related to the importance of specific modes, terminals, and corridors. Concerning passenger transportation, the substitution effect supported by information technologies can lead to a recovery, resulting in lower demands, such as commuting and even social interactions. As organizations realize the convenience of remote work for specific tasks, they may reduce their office footprints and the associated commuting patterns.

Concerning freight, the deferred demand effect, changing consumer patterns, and public economic policies can have substantial impacts, with the recovery resulting in demand surges. Transportation systems do not handle surges well since capacity is expensive to add without a constant demand. This can create difficulties for freight terminals such as ports, creating bottlenecks at critical gateways, tying up transport capacity, and exacerbating shortages. As a pandemic exposes specific vulnerabilities within supply chains, such as concentration, changes in sourcing to reduce risk, including re-shoring, can also be observed. This involves re-evaluating the just-in-time model for critical supply chains as cargo owners seek more accessible and resilient suppliers.

COVID-19 was a global crisis, but taking place in a context where each nation-state is responsible for its national health policy and associated restrictions concerning transportation and trade. Evaluating the effectiveness of pandemic recovery measures in the transportation sector remains challenging, with several perceived best practices.

• Revise policy and investment strategies. A pandemic can accelerate or slow ongoing transformations in the transportation sector. This allows governments and enterprises to revise and reassess investments in infrastructures and modes, either through delays or acceleration.
• Prioritize measures to reflect risk factors. Lockdowns and restrictions seriously affected mobility and opportunities for consumers and labor, particularly for the retail sector and its supply chains. It was observed during COVID-19 that overreactions, such as complete lockdowns, can have significantly more damaging economic and social effects than epidemiological benefits.
• Support digitalization. Since a pandemic is likely to accelerate the transition toward new business models, digitalization is a strategy supporting substituting from several forms of mobility and potential contacts. During COVID-19, this was reflected in the growth of online activity, including e-commerce, but also in the digitalization of social interactions and business transactions.
• Expand the resilience of transportation. A pandemic is a stress test over the capacity and operations of transportation modes and terminals, which allows for identifying key bottlenecks. While COVID-19 focused on supply chain crisis management with their ad hoc responses, the situation is evolving toward supply chain resilience as a proactive strategic objective.

A major problem is estimating post-pandemic demand, as a pandemic can disrupt price sensitivity mechanisms and demand patterns and be simultaneously inflationary and deflationary.

---

Related Topics

• 9.3 – Transport Safety and Security
• 9.4 – Transportation, Disruptions and Resilience
• B.14 – The Logistics of Global Food Systems
• 5.5 – Air Transport
• 7.2 – Globalization and International Trade

Bibliography

• Luke, T.C. and J-P Rodrigue (2008) “Protecting Public Health and Global Freight Transportation Systems during an Influenza Pandemic”, American Journal of Disaster Medicine, Vol. 3, No. 2., pp. 99-107.
• National Academies of Sciences, Engineering, and Medicine (2014) A Guide to Regional Transportation Planning for Disasters, Emergencies, and Significant Events. Washington, DC: The National Academies Press.
• Nicolaides C, L. Cueto-Felgueroso, M.C. González and R. Juanes (2012) “A Metric of Influential Spreading during Contagion Dynamics through the Air Transportation Network”, PLOS ONE 7(7).
• ITF (2020) Transport Policy Responses to the Coronavirus Crisis, Covid-19 Transport Brief.
• US DOT (2022) Supply Chain Assessment of the Transportation Industrial Base: Freight and Logistics.