“Several Asian and Sub-Sahara Africa regions report a COVID-19 death rate that’s 1% of the U.S. rate.”
– S. Mukherjee, MD “The COVID Conundrum”, New Yorker Magazine, March 1, 2021
Siddhartha Mukherjee, the “other” brillant American-Indian physician-writer for the New Yorker, other than Atul Gwande that is, recently summarized the speculations about why COVID death rates vary so widely among countries.
Poverty?
Dharavi, Asia’s largest slum, in Mumbai (using NYC data) predicted 3-5,000 COVID deaths; actual COVID deaths: less than 1000.
“The field hospital was packed up and taken away.”
Bangladesh with 63 million people had a COVID death rate 3.5% of the U.S.
“Rich countries, with the most sophisticated health-care systems seem to have suffered the worst devastation of the disease.”
Population?
India with1.3 billion people had a COVID death rate 10% of U.S.
Nigeria with 200 million people had a COVID death rate one-hundredth of the U.S.
Pakistan with 220 million people had a predicted rate of 650,000 deaths; actual 2020 COVID deaths: 12,000.
Ghana with 30 million people predicted 75,000 deaths; actual 2020 COVID deaths: 300.
Age?
Both India and Mexico’s median age’s is 28 years. India’s COVID death rate is less than 10% of Mexico’s.
Distribution of elderly?
The U.S. “warehouses” its elderly in nursing home. In developing countries the elderly are “homebound’ with their own families.“ About one-third of the deaths in the U.S.have occurred among the occupants and staff of long-term nursing homes.”
Different clinical courses?
Lagos, Nigeria, a “city like New York on steroids”, prepared for an onslaught of the severely ill. Their field hospitals and isolation wards became 75-90% filled, but their ICUs were empty. “Patients were mostly mildly symptomatic. Street life in Lagos remained chaotic, bustling, and with full bore marketplaces as London went into lock down.”
Systemic underreporting?
The WHO knows that only about 25% of malaria deaths are reported globally. In poor countries most COVID deaths will occur at home. A select detailed study of deaths in Zambia strongly suggested that the true COVID death rate there was probably 10 times higher than the official one. But, In India a longitudinal household survey (hospitals not included) showed that the death rates from ALL CAUSES in May-August 2020 were twice that of the same period in 2015. A detailed analysis of the data, however, “did not reveal the telltale signature of COVID re: age, location, and gender”.
Delayed appearance?
Recent studies in India and Nigeria show that close to half of the population were already positive for coronavirus antibodies in 2020, so unless there are later surges, which could still happen, the appearance of COVID was not delayed in those countries.
Different levels of governmental response?
Rwanda, a poor country of 13 million, had only 100 COVID deaths in 2020 due in part to “clear and decisive control measures, aggressive enforcement of protection protocols, and a strong data center with fast ‘whack-a-mole’ responses to outbreaks.” The U.S. “has suffered grievously from corresponding weakness.”
Viral dose-related?
Many infected Indian patients had very low virus loads in their blood. Maybe living outdoors or in huts with no windows and balmy breezes in the warmer parts of the world results in a smaller dose of virus inhaled by the patients, causing less severe disease. This concept is compatible with the U.S. experience of young health care workers tending to COVID ICU patients having disproportionally severe illness when they themselves became infected..
Previously acquired immunity?
This might be a big part of the answer. Studies in different countries discovered that from 25% to 40% of people had other coronavirus, mild cold viruses, antibodies in their blood BEFORE they were included in a COVID SARS-CoV-2 antibody prevalence study. This suggests that immunity from other non-lethal coronaviruses may partially protect against the SARS-CoV-2 virus. This “cross-reactivity” of immunity suggests that this “novel” coronavirus wasn’t entirely “novel”; that many coronaviruses share spike proteins that may induce immunity to other coronaviruses. A study in Boston that those COVID-19 patients that had antibodies to other CoV viruses had “lower rates of mechanical ventilation, fewer ICU admissions, and significantly fewer deaths” when they got COVID. Other studies have not confirmed that small study, but if true it could explain some of the regional differences in COVID-19 and could be one of the reasons for the wide spectrum of severity of symptoms in COVID-19 throughout the world.
“Ockham’s razor”, a mainstay of diagnostic medicine and scientific problem-solving, states that faced with multiple answers as to the cause of an event, choose the simplest one. S. Mukherjee describes this pandemic crisis obviously as one of “combined social and biological forces”, and given the complexity of the analysis of the causes of our different experiences, he suggests substituting the term, “Ockham’s quilt”. This is not surprising coming from him, an expert in oncology, a field that long ago soured on the concept of searching for the “one” cause of cancer.
Of all of the reasons listed briefly here contributing to the regional differences in the COVID-19 lethalness, the concept of cross-reactive immunity is the most intriguing to me. It is one that you will undoubtedly hear much more about as COVID “variants” proliferate. “It ain’t over yet”.
As one wit said, “We can see the light at the end of the tunnel, BUT that means that we are still IN the tunnel.”
My next blogs are March 15 on “COVID Variants and Vaccines” followed by my annual April 1st surprise.
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