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Slow, quick and slow: The viral spread in the developing world

The spread of the coronavirus in developing countries is likely to follow a slow-quick-slow pattern explained by external connectivity, urban density and urbanization.

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Credit: Alasdair Rae

Given limited testing, we will never truly be able to tell with significant confidence how the coronavirus has spread across countries. But we can hypothesize how structural features of developing countries will have likely aided or hindered the path and speed of transmission. Let’s discuss three of them. 
 

Limited external connectivity

By now the virus has reached every continent, with Antarctica being the latest casualty as of December 2020. The pandemic has spread to virtually every single country and territory around the world.  

That was (naturally) not the case in the beginning. While there is continued discussion about whether indeed the virus originated in China, Wuhan was indeed the locus of the first major outbreak that caught the international spotlight. 

Soon after this initial outbreak, neighboring countries, a few cruise ships and increasingly a broader group of countries around the world spotted coronavirus infections as they ramped up testing. 

But it were the well-connected global centers of commerce and trade that visibly suffered the biggest outbreaks. It comes as no surprise that a place like New York City, which is so extensively externally connected, became the epicenter of a major outbreak. But before the US, it were the countries in Europe which were particularly badly hit, including the industrious industrial north of Italy.

Enters globalization. Globalization has fueled an intensification of all sorts of linkages across borders but its extent has varied drastically across types of markets. Information markets as well as financial markets are the most integrated internationally. Goods and especially services markets remain less integrated as do labor markets. The latter which is connected to the  cross-border mobility of people matters most in this context.

The point is that virtually all countries have participated over the past four and especially last two decades in the process of globalization. But some have remained much less externally connected than others, such as parts of Latin America and Africa. This more limited external connectivity has likely slowed the initial phase of the spread. 

High urban density 

The customary port of entry into a country is for most travelers a city. That’s the case too for viruses. So when the coronavirus travelled across borders, it will have likely found its way into urban settings first.

Cities in many developing countries exhibit environmental characteristics that are conducive to transmission. Think of high urban density, coupled with poverty and informality. People live, work and play in settings where physical distancing is more difficult.  The latest estimates suggest that respectively 65 and 27 percent of urban populations in LICs and MICs live in slums. The lack of sanitary conditions is likely to amplify the spread of the virus further. 

The multigenerational structure and large size of households in lower-income countries adds another layer of complexity, particularly given that a large share of the transmission happens in the pre-symptomatic stage.

This then likely explains why infection spreads like wildfire once it has reached a critical mass in developing country cities, with poverty, informality and the lack of social safety nets also limiting the effectiveness of containment and suppression policies.
 

Limited urbanization

The reason why afterwards the pace slows down again is the limited internal connectivity in many countries between urban and rural settings. Rural hinterlands are also characterized by much-lower density, limiting thereby the potential for transmission.
 
Urbanization (the share of people living in urban settings) is a useful metric in this respect. It varies dramatically across developing region (see the chart). The Latin America and the Caribbean region is the most urbanized developing region, with 80% of its population living in urban areas. Compare this to Sub-Saharan Africa (40%) and South Asia (34%), where larger rural population shares will offer a measure of protection against rapid transmission.
 
There are many other influences at play, but one could argue that it did not come as a surprise that Latin America was more exposed than other regions due its high degree of urbanization.  

Slow, quick, slow

That’s the putative pattern for transmission around the developing world, with of course large differences across countries. What does it mean for the future trajectory of this pandemic?
 
In a recent blog and research paper, we argued that the dichotomy in pandemic outcomes between rich and poor countries is partly unreal and partly unrealized. The unreal part reflects differences in data quality and continues to hold relevance today (a subject worthy of another blog). But the unrealized part remains equally important. The progression of the pandemic across and within countries is happening in uneven stages with unequal speeds. 
 
Looking ahead, we should be concerned that existing variants have not yet fully propagated through the developing world as the last stage takes time. But even more worrisome is the emergence of the new variants and also the “new new variants” of the future. These will generate new impulses, which will take a long time to work their full way through this long-winded transmission mechanism. 
 
All the more reason to deploy the vaccines with urgency, including to the poorer developing countries which will otherwise would continue to provide fertile ground for new variations of the virus. And that would eventually come back to haunt us all.