Thursday, 3 April 2014

Malaria Killed Half the People Who Have Ever Lived

Malaria killed half the people who have ever lived. This surprising statement pops up from time to time; in fact, I found a variation of it in a 2002 Nature article by John Whitfield, and Nature is usually a trustworthy source. But is this true? Could it be true?

How Many People Have Ever Lived?

In many human conflicts, the casualties due to
malaria have exceeded those of battle. Image
courtesy of U.S. National Archives and Records
Administration.

Of course we can’t know for sure how many people have ever lived - we don’t have census data going back 52,000 years – but fortunately, someone has tried to guesstimate the answer to this question. Carl Haub, of the Population Reference Bureau came up with a number, despite the fact that “any such exercise can be only a highly speculative enterprise:" roughly 108 billion people have been born.

Therefore, working with Haub’s numbers, if malaria has killed half the people who ever lived, 54 billion people have died from malaria.

How Many People Die From Malaria?


Estimates of the number of annual deaths from malaria differ quite widely. One of the reasons for this is that we still don’t have accurate records. One statistic often quoted is that, today, malaria kills about one million people every year, most of them children. This prompts reflection on a couple of points that are worth acknowledging:
•    Most people who die from malaria are killed before they have a chance to reproduce, which means that the disease will have had a very significant impact on population, even if it hasn’t literally killed half of all humans.
•    Malaria is especially serious during pregnancy, leading to septic abortion, still birth, and poor health in newborns. The WHO states that low birth weight due to malaria in pregnancy contributes significantly to infant mortality; therefore, babies conceived but born dead, and infant deaths indirectly due to malaria are significant as well.

The World Health Report 1999 (WHO) states that “during the first half of the 20th century, the world sustained around 2 million deaths from malaria each year,” so for that period alone, there were a hundred million deaths.

After that, mortality was halved by better treatment and eradication efforts, so we’ll add another 64 million deaths. This is the only part of human history for which we have even roughly accurate numbers.

Malaria Deaths Before 1900


Malaria is the only one of the major epidemic killers of humans that is thought to have been with us throughout our entire evolution, so the death toll started right at the beginning, though numbers were likely low until we had permanent settlements with larger populations.

According to Carl Haub, more than 96 billion people, out of 108 billion, lived before 1900, with more than 85 billion born between 8000BC and 1650. During most of this time, there were essentially no cures for malaria and people would have settled down in permanent settlements, allowing for high transmission of the disease. How many did malaria kill? We still have most of our 54 billion deaths to account for.

If most of these people died between 8000BC and 1650, that would mean an average death rate of 5 ½ million per year. Is that possible?

Again, there are a few other important points to note:

•    Until relatively recently, Plasmodium falciparum, the species that kills, was nearly cosmopolitan (Roberts and Janovy).
•    Before the days of modern medicine, infectious disease was the major killer of humans, and the reason why life expectancy was much lower.
•    Malaria does cause epidemics, but where it is endemic, it is typically present continuously and all year round. Other diseases, such as smallpox, flu, measles, cholera, and plague strike as epidemics and then disappear, often for long periods of time.

R. S. Bray writes: “Morbidity and mortality due to malaria worldwide were greater than any other disease… a world-wide epidemic of enormous proportions (89).”

Other historians tell us that

•    “The Portuguese... had imported so many African slaves into Portugal by the late fifteenth century that their falciparum malaria ignited a series of epidemics so intense that the Tagus valley was almost depopulated (Desowitz, 77).”
•    “Malaria throughout the tropical Old World, cholera in tropical Southeast Asia, and Yellow Fever in tropical Africa were (and still are) the most notorious of tropical killers (Diamond, 214).” (my emphasis)
•    Accounts of European settlements in the tropics and other populations report greater than 90% death toll from malaria and other tropical diseases.
•    “For centuries, malaria has outranked warfare as a source of human suffering (John F. Kennedy).”

Desowitz quotes the U.S. Public Health Service, 1919: “for the South as a whole it is safe to say that typhoid fever, dysentery, pellagra, and tuberculosis, all together, are not as important as malaria.” Desowitz notes that this would be equally valid for the preceding 200 years.

Has Malaria Killed Half the People Who Have Ever Lived?


So did malaria kill between 53 and 54 billion of the 96 billion who lived before 1900? I’m neither an epidemiologist nor a statistician, and I had limited (secondary) sources to work with. We’ll never know for sure, but based on my reading I think it’s possible.

If we also consider deaths indirectly due to malaria – and here I’ll also invoke the parasite theory of human values/morals, which suggests that much war and other violence is, at its root, due to infectious disease – I think it’s indisputable.

Resources


Bray, R. S. 1996. Armies of Pestilence: The Impact of Disease on History. New York: Barnes & Noble.

Desowitz, Robert S. 1997. Who Gave Pinta to the Santa Maria?: Torrid Diseases in a Temperate World. New York: W. W. Norton and Co.

Diamond, Jared. 1997. Guns, Germs, and Steel: The Fates of Human Societies. New York: W. W. Norton and Co.

Haub, Carl. 2011. “How Many People Have Ever Lived on Earth?” Population Reference Bureau.

Roberts, Larry S., and John Janovy Jr. 2009. Gerald D. Schmidt & Larry S. Roberts’ Foundations of Parasitology. Boston, McGraw Hill.

Whitfield, John. 2002. “Portrait of a Serial Killer: A Roundup of the History and Biology of the Malaria Parasite.” Nature. doi:10.1038/news021001-6

WHO. “Rolling Back Malaria.” The World Health Report 1999. p. 49 – 63.


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