We have been focused on fighting COVID-19 as it impacts the U.S. and the industrialized world, but what will happen when the pandemic continues its spread into developing nations? The recent news that poorer countries weigh reopening despite rising numbers of cases makes this an even more urgent question.

Poor countries, with their lack of resources, poor medical coverage, and densely populated towns and cities, maybe facing an unprecedented disaster as the pandemic strikes them. And because the world has shrunk, spread to low-income countries will also impact the U.S.

In late March, modelers at the Imperial College, London estimated that without intervention, seven-billion people could be infected with COVID, with 40 million deaths this year, the largest burden falling on low-income countries (average annual per-capita income of <996 USD).

They believed that by focusing on protecting the elderly and social distancing, mortality could be halved, but how the disease will affect low-and middle-income countries may not replicate our experience or that of other high-income nations. 

Given how easily the virus is transmitted and its virulence in the U.S. and Western Europe, we’d expect high infection and death rates in every affected country. However, there are huge disparities in the reported rates between richer and poor countries. 

To date, high-income countries have been hit hardest, with the U.S., Italy, the UK, Spain, and France accounting for 70 percent of global deaths. As of Memorial Day, the U.S. reported close to 100,000 COVID deaths, which translates to a rate of .3 per thousand. Italy, another high-income country, reported 33,000 deaths, .544 deaths per thousand.

Conversely, India, densely populated with widespread poverty, has reported 4,172 deaths (only .003 per thousand) as of Memorial Day, while resource-poor Chad and Ghana reported 61 and 32 deaths respectively. These and lower-middle-income countries account for half of the global population, but only two percent of the global death toll attributed to COVID-19. Has COVID-19 spread unevenly, as some have hypothesized, or is there a more complex equation that also factors-in population demographics and density, and the scope and speed of nations’ public health responses?

A recent Brookings Institution report hypothesizes that the disparity in mortality figures between rich and poor nations is greatly exaggerated. That’s likely since testing is so spotty — especially in the developing world, but there are definite reasons why some countries are hit harder than others and why countries with seemingly identical geographies may have big disparities in the number of cases. For example, the Dominican Republic reports 15,073 cases, while Haiti, the country that shares the island of Hispaniola, reports only 958 as of Memorial Day.

Age is a big factor. Modelers reported in The Lancet that China’s estimated case fatality rate for infected patients under 60 was only .32 percent, while those 60+ had a fatality rate of 6.4 percent, and those aged 8 or over had the highest rate at 18.5 percent. The death rates among other nations with large populations of people over 60, such as Italy and the U.S., are similar. 

Conversely, low-income countries (per capita income less than $1,000 per year) have fewer resources and lower life expectancy. They have much smaller proportions of people over 65 (3 percent on average) than wealthy, low-fertility nations (17.4 percent). That could work in their favor; the Imperial College estimates that coronavirus would kill .39 percent of Bangladesh’s population and 0.21 percent of the sub-Saharan African population, less than half the 0.8 percent mortality rate estimated for the U.S. and other Organisation for Economic Co-operation and Development countries.

Additionally, we know that less healthy individuals with underlying conditions including diabetes, lung disease, cardiovascular disease, kidney disease, hypertension and obesity, are particularly vulnerable. While extremely common in industrialized nations, the conditions are less common in the developing world, though that is changing.

COVID-19’s impact in countries with limited medical resources could be huge. It’s been reported that Uganda has 0.1 intensive-care unit beds per 100,000 people, compared with 34.7 in the U.S.; South Sudan has 24 intensive care units and just four ventilators in the whole country.

As COVID-19 became more widespread and medical need became more acute in March, analytics company GlobalData estimated need for an additional 880,000 ventilators globally, while the Society of Critical Care Medicine projected that as many as 960,000 may have needed to be put on ventilators. A month later, these estimates seemed conservative; an April 20th report in the Lancet estimated peak need at 120,000 invasive and 100,00 non-invasive ventilators in the U.S. alone. 

While we don’t yet know how population density will play out in developing nations, we do know crowding exacerbates the spread of disease and that lockdowns discouraging transmission can backfire. India’s 1.3 billion people — many of whom are working in the informal economy — face disaster if lockdowns continue for a prolonged period. India is seeing reverse migration as thousands, deprived of their means of survival in cities, return to their villages, raising the prospect of COVID-19 spreading to rural areas where sanitation, water quality and public health infrastructure are even more inadequate than in cities. The impossibility of physical distancing in India’s crowded cities and villages, India’s lack of testing (only 385 tests per million, as opposed to 21,000 per million in Italy), and the economic hardship and human suffering that occurs in lockdowns suggest a different path may be needed in the developing world.

One approach that’s been put forward for areas with the possibility of high transmission rates is pursuing herd immunity. A team of researchers at Princeton and the Center for Disease Dynamics, Economics and Policy identified India as a place where this strategy could succeed. By allowing the virus to be unleashed in a controlled way for the next seven months, they estimate 60 percent of the country’s people would be immune by November, thus halting disease progression. They believe that mortality could be low given that 93.5 percent of the Indian population is younger than 65, and presumably more resilient, though no projections were shared.

Could this work? It has not been proven that immunity lasts, though early studies are somewhat encouraging, and COVID-19 has, so far, been slow to mutate. Sweden’s experiment in herd immunity has yielded lessons; their laissez-faire approach to physical distancing and keeping businesses open has kept their economy stronger and their population less psychologically stressed. But their push to attain herd immunity hasn’t worked, resulting in a higher proportion of preventable deaths among the elderly and chronically ill than in other European nations that pursued lockdowns. These mixed results suggest a middle ground would have been possible and preferred.

We have also learned that borders are porous. COVID-19 has been much easier to control in island nations such as Australia and New Zealand than elsewhere. Still, screening those who enter a country has proven to be impractical with the high proportion of cases that are asymptomatic. Therefore, 14-day quarantine policies have become common, but enforcement varies. Further, testing for the disease remains low in most countries. The result is a poor picture of the actual impact and spread of COVID-19. Hit particularly hard are countries that depend on tourism. And in all countries, the economic hardship is falling most heavily on its poorest citizens.

Looking ahead, news of promising vaccines in development means that we are likely to see one or more chosen for manufacture in a ramped-up timeline, but the time required to produce large numbers of doses will initially yield a constrained supply. History teaches us that low resource countries are unlikely to be first in line to receive the vaccine. This can only deepen the health and economic divisions that represent social injustice.

Jonathan Fielding M.D., who headed public health for Massachusetts and Los Angeles County, is a UCLA professor of Health Policy and Management.