Official global tallies of COVID-19 passed 3 million deaths on the weekend. The current pandemic was already one of the 10 worst recorded appearances of infectious disease in history, but thankfully it remains nowhere near the worst of the worst.
Three months ago, diagnosed cases of COVID passed 100,000 million. Grim as that milestone was, it coincided with falling rates per day and vaccine approvals. There were grounds for hope the worst might be behind us. Instead, global positive tests started rising again a month later, and are setting new daily records.
“Around the world, cases and deaths are continuing to increase at worrying rates,” World Health Organization (WHO) Director-General Tedros Adhanom Ghebreyesus said in a briefing on April 16. "The number of new cases per week has nearly doubled over the past two months."
Half of America's adults are now vaccinated, but most of the world remains a long way off access to enough vaccines to halt the toll, making many more deaths inevitable, but already the toll is well past some of the great plagues of the past.
The 3 million deaths officially attributed to COVID-19 are almost certainly an underestimate. In many parts of the world, particularly places where testing facilities are inadequate, excess mortality has drastically exceeded COVID-19 statistics. Nevertheless, this is still easily the best documented pandemic in history. Estimates for historical plagues often vary by a factor of 10, in addition to the questions of whether multiple outbreaks of a disease that never quite went away should be counted together or separately. Comparing Long COVID with non-lethal effects of diseases past is almost impossible.
Nevertheless, we know that awful as the last year has been, this is not history's worst plague.
The Black Death is thought to have killed up to 200 million people in seven years, including a third of the population of Europe at the time. Over many centuries smallpox probably killed more people still, possibly 500 million by some estimates, with tens of millions dying within a few years of its introduction to Central America.
It's difficult to directly compare other catastrophic outbreaks but two others are notable for their grim statistics: the Plague of Justinian may have killed 12 million in 541-542 CE and the ongoing AIDS crisis, which has taken at least 30 million lives over the past 40 years.
Despite erroneous comparisons to the flu, the current crisis looks nothing like any influenza epidemic. The 1918-19 pandemic, popularly knows as the Spanish flu killed an estimated 20-50 million people (some say 100 million). On the other hand, COVID-19 has already killed around three times as many people as the second-worst influenza epidemic.
Infectious diseases are estimated to have caused more deaths than the one we are experiencing at least three other times. In 1855, Asia was struck by what was known as “The Third Plague”, with an estimated death toll of 10-12 million. The second century's Antonine Plague (possibly smallpox), and Mexico's Cocoliztli Epidemic each probably killed at least 5 million but COVID has now overtaken estimates of every other disease outbreak humanity has ever faced.
The world population has grown so much this century that many epidemics that caused a small fraction of COVID-19's deaths still killed a larger proportion of the global population of the time. It's a matter of opinion whether raw numbers, or proportion of the era's population is the best way to rank diseases.