The plague struck everyone, even those who had previously been perfectly healthy. Those affected developed a fever and stank from the mouth, their eyes became inflamed, coughing and vomiting followed, and many suffered from cramps. This is reported by the Athenian writer Thucydides in his history of the Peloponnesian War. Pustules and ulcers appeared on the skin of the sick, leaving scars. The streets of Athens filled with the dead. Doctors didn’t know what to do, they themselves died in droves. Animals that had nibbled on the corpses also died. But at least there was a glimmer of hope, according to Thucydides: whoever had survived the plague once, like himself, did not get sick a second time. Or at least not that difficult anymore.
What afflicted the Athenians in that early summer of 430 BC has gone down in history as the “Attic Plague”. According to Thucydides, contemporaries initially believed that the enemy Spartans had poisoned the water. Then there was talk of an epidemic imported from Africa. Later historians have speculated on dozens of diseases. The only thing that is certain is that it wasn’t the bubonic plague transmitted by rat fleas, because rats only came to Europe in Roman times. But what actually lies behind the Attic plague can hardly be clarified today.
The same applies to other plagues of antiquity that are still a mystery today, for example the so-called Antonine plague, which raged in the Roman Empire for years around 170 AD. Or for the disease that disfigured the face of the Egyptian pharaoh Ramses V, who ruled the late Egyptian New Kingdom for four years in the 12th century BC, until he died of unknown causes.
Smallpox kills hundreds of millions of people in the 20th century
However, Italian microbiologists are now bringing a new disease into play that had actually already been eliminated from the list of suspects: smallpox. In fact, Thucydides’ descriptions sound suspiciously like this infectious disease. Ancient descriptions of the Antonine plague are also reminiscent of the viruses of the Orthopoxvirus variolae genus, which killed hundreds of millions of people in the 20th century before being eradicated in laboratories in 1980 except for the remains.
Original analyzes of the mutations in the genome of smallpox viruses suggested that the deadly pathogens could not have originated before the 18th century – and that they can be traced back to an older predecessor, which, however, may not have originated until the 16th century ADe, i.e. two millennia after the Attic plague and more than a millennium after the Antonine plague. So it couldn’t have been smallpox.
But that judgment may have been a bit hasty. Most recently, researchers have already demonstrated that a previously unknown branch of variolaviruses, which later became extinct, was widespread in Scandinavia in the early Middle Ages. And now microbiologists working with Diego Forni from the IRCCS Eugenio Medea research institute north of Milan have backdated the origin of the pathogens even further. As in the magazine Microbial Genomics to report, the origin of the smallpox virus probably goes back to a last predecessor about 4000 years ago. The viruses would therefore be so old that they could easily have been responsible for both the Attic plague and the Antonine plague – and Ramses V. could also have been a victim of smallpox.
Genes change much faster in the short term than in the long term
The researchers around Forni are not based on possibly newly discovered smallpox viruses from antiquity. Rather, they reanalyzed known virus data, reconsidering what scientists call the “time-dependent rate phenomenon.” How quickly an organism appears to change evolutionarily therefore depends on which time scale is applied. To put it simply, genomes change much faster in the short term than in the long term; the phenomenon challenges previous calculations of the speed of evolution. According to the team, this also applies to the smallpox virus.
“The variola virus could be much, much older than we thought”, said Forni of the British Microbiology Society. This confirms historical reports of smallpox outbreaks in ancient societies and hopefully also helps settle the controversy over the evolutionary age of smallpox.
Whether it was actually smallpox, for example, which was rampant in Athens at the time of the Peloponnesian War, is not clear – in order to decide that, one would have to find clear traces of the virus in well-preserved corpses from that time. Until then, what historical plagues like the Attic plague were all about is as unclear as ever.