Globalization and spread of infectious disease

Globalization involves accelerated transcontinental streaming of goods, people, capital, information, and energy across borders, frequently empowered by technological developments.  The dissemination of infectious diseases worldwide has followed a parallel trend. Since the prehistoric era, an enormous breeding ground was created as Europe, Asia, and North America became connected by world trade routes. During the Antonine Plague, smallpox emerged in Rome killing millions of Roman people from 165 AD to 180 AD. After 300 years Europe was afflicted by the bubonic plague as the Plague of Justinian (542-543 AD). This bubonic plague re-emerged in the 14^th century in more severe form as the Black Death with the initiation of a new trade route with China that prompted rapid transmission of flea-infested furs from plague-ridden Central Asia.

Before the expansion of world trade routes, the spread of human pathogens predominantly occurred in two ways.

1. With the livelihood as a hunter-gatherer, people lived a life in motion. So it was challenging for the microorganisms to come in contact with their human host for a long period. As people started colonizing in large numbers in the same space with farming as an occupation, they were in prolonged contact with each other and also with their fecal matter that increased the chance of disease transmission.
2. With the establishment of towns and cities even larger numbers of people came in closer proximity under even worse sanitary conditions.

After two millennia as the human civilization proudly embraced a new era of globalization in terms of faster travel over greater distances and worldwide trade, the human pathogens also took the golden opportunity to disseminate following the same route. At the beginning of19^thcentury, the emergence of plague epidemics in several port cities all over the world demonstrated the remarkable influence of increased trade and travel on infectious diseases. In Johannesburg, the incidence of the plague led to the relocation of black residents as white colonists believed them to be the source of the disease. Almost at the same time, human civilization witnessed the death of millions of people worldwide due to the influenza pandemic. Thus with the current era of globalization, population density is becoming higher, millions of people are moving around the world very fast (by choice or by force), food, animals, capitals and other daily commodities are freely getting transported across political boundaries. In the course of this process, pathogens are getting plenty of opportunities to hitch rides all around the world using humans, commodities, airplanes, and other conveyances as vehicles. Regardless of the successful endeavors of the developed world to control and even eradicate several infectious diseases, every year around 13 million people still die from such diseases.

In the last two centuries, the average distance of human travel with speed has amplified a thousand-fold together with the number of people traveling at a time, while incubation periods for infectious diseases continued to be the same as before. Previously what could have been a merely localized outbreak, now can progress into a large, worldwide epidemic in a matter of days. The global spread of AIDS is a singular, but the most devastating, instance of the impact of this tremendous human mobility on infectious disease.

Open borders and international travel opportunities complemented by advances in transportation technology are availed not only by the tourists; but also by millions of other people who leave their homeland in search of a job or an improved quality of life, and several more who are forcefully displaced by war. Such migrant populations are among the most vulnerable to emerging infectious diseases. The emergence and re-emergence of infectious diseases like multidrug-resistant tuberculosis in developed countries are often reported to be associated with the massive influx of immigrants from poor countries with a higher prevalence of such diseases. It is expected that the situation will deteriorate more in the future with the growth of the world population along with an increase in demographic and economic gaps between the developed and developing worlds that will instigate people to move out in search of a better quality of life. In the context of transportation, an airplane transporting an infected mosquito vector in the wheel wells was hypothesized to be the vehicle for the introduction of the West Nile virus into the United States in 1999 for the first time.

Previously, most food products have been manufactured and consumed locally. However, over the last few decades, with the rise in consumer demand and adaptation of westernized lifestyle together with food production and processing activities being geographically more fragmented, the epidemiology of the foodborne disease has changed significantly. Before the establishment of WTO in 1995, trade in animals and animal products were conducted following a policy of zero risks. But at present, imported products are treated similarly to domestic products, even as animal health restrictions are considered. The experience of bovine spongiform encephalopathy in the United Kingdom and Europe exemplifies the remarkable threat that accompanies the unlimited growth and opportunity offered by new international trade regulations enforced by WTO. Many countries do not have all-inclusive food safety programs incorporated into their public health strategies. Outbreaks of foodborne illness have revealed many shortcomings in food safety regulation practices not only in developing countries but also in developed countries like the United States. The free flow of food also elevates serious concerns about the global spread of antibiotic resistance associated with the consumption of antibiotic-fed food animals.

Similar aspects make the situation more complex as novel diseases emerge and spread out very fast causing unprecedented pandemics like SARS in 2002-2004 and COVID 19 in 2019-2020. Thus as we dream to progress using technological advancement as a vehicle towards a borderless world through globalization, often we are forced to halt and take several steps back as the pandemics are jeopardizing public health and socio-economic conditions all around the world. We hope, utilizing the seamless global communication and scientific development as devices of globalization in real-time, proper treatment measures will soon be invented and implemented to control, if not eradicate the life-threatening diseases from the world.