COVID-19 Death Rates

Why COVID-19 death rates in poorer countries remain far, far lower than richer countries is a question that intrigues many. Best-selling author Siddhartha Mukherjee’s analysis of the subject is nuanced. As icing on the cake, given his Indian connections, there’s a lot of India-specific information.

 

Many feel the average age of different countries has a big role to play. After all:

“After the age of thirty, your chance of dying if you get covid-19 doubles roughly every eight years.”

But in India, he says that old people seem resilient, many of those “in their seventies and eighties” who contracted COVID-19” have “bounced back”.

 

Or is it that the “spatial distribution of the elderly” matters? In India and poorer countries, the elderly are generally with (younger) family. Whereas in the West, they’re concentrated in old age homes where it spreads like wildfire.

 

Perhaps average age is too broad a categorization. Do the details of age distribution matter, the “so-called population pyramid”? But then:

“Mexico has a median age similar to India’s; the percentage of the population that’s over sixty-five is within a point or two of India’s. Yet India’s reported rate of covid-19 deaths per capita is less than a tenth of Mexico’s.”

 

Dharavi is Asia’s largest slum. Predictions were dire:

“If the fatality rate from the “New York wave” of the pandemic were extrapolated, between three thousand and five thousand people would be expected to die in Dharavi.”

But what played out was very, very different:

“Yet by mid-fall Dharavi had only a few hundred reported deaths—a tenth of what was expected—and the municipal government announced plans to pack up the field hospital there.”

 

Is it that the West reports accurately, whereas the rest don’t, either for political reasons or due to the lack of a healthcare system that can cover enough, or factors like daily wages workers who can’t afford to be quarantined and therefore don’t report themselves? All possibilities, yes. Then again:

“Countries like Ghana and Nigeria sought and received billions of dollars in foreign assistance to help them combat the virus.”

Surely such countries have an incentive to be more accurate. But their death tolls are far lower than the West.

 

Proxies were used to try and identify such under-reporting:

“Public-health experts have a saying: “It’s hard to hide bodies.” So a surge of deaths under any description—“all-cause mortality”—might help us glimpse the true dimension of the problem.”

In India, “all-cause mortality” had indeed doubled between May and August. But:

“When his researchers analyzed the data by age, location, and gender, they found that excess deaths tended to be observed in younger cohorts, and in rural rather than in urban settings; nor was there evidence of the usual coronavirus skew toward greater lethality in men. “The telltale signatures of covid just aren’t there,” he said.”

Instead, the spike in deaths might have been due to “wage loss, displacement, malnourishment, forced migration, and disruptions in health care—the skipped clinic visit for malaria, diabetes, TB, or hypertension”.

 

Then there are those random seroprevalence tests (“individuals who test positive for antibodies”). In July and August, such tests in Karnataka suggested “nearly half the population had been infected at some point”. Are Indians (and those in many, but not all, poorer countries) more resilient?

 

That would explain a weird observation. T-cells in the body hunt for invaders. And they have memory. In poorer countries, something weird was noticed:

“The new coronavirus was somehow triggering a T-cell response. These T cells were acting as if they’d recognized a virus they had assuredly never before encountered.”

How could that be possible?

“Part of the answer may have to do with how T cells recognize pathogens. It’s natural to think of our memory T cells as brandishing a criminal’s mug shot. But what they “remember” is more like the curve of a nostril, the shape of an ear—distinctive snippets of a larger protein picture. Now, suppose a former intruder’s much worse cousin shows up; it’s a fresh face, but it shares a family trait—maybe those batwing ears—that could alert at least some of the memory T cells. Could the novel coronavirus share such traits with previously circulating pathogens?”

Inhabitants of poorer countries have been exposed to many, many more pathogens than those of the sanitized West. Maybe the coronavirus is a “close cousin” of other pathogens experienced earlier.

 

Or maybe it’s the dosage of the virus? Open-air ventilation is the norm in poorer countries, which may cause the dosage to get diluted. The West, with its AC-based, closed rooms and buildings may have concentrated the doses.

 

No conclusive answers. And Mukherjee reminds us why:

“Epidemiology isn’t physics. Human bodies are not Newtonian bodies.”

Plus, like Agatha Christie’s Murder on the Orient Express, where the murderer wasn’t one person, but a group:

“(COVID-19 may be the) epidemiological version of that mystery on the Orient Express: there’s no one culprit but many.”

Lastly, he reminds us that the story ain’t over:

“What’s needed is humility in the face of an intricately evolving body of evidence. The pandemic could well drift or shift into something that defies our best efforts to model and characterize it.”