In the tooth of a 6-year-old kid killed by the Plague around 1,500 years ago, scientists have identified the earliest known case of a Haemophilus influenzae serotype b (HiB) infection, a disease that was a leading cause of bacterial meningitis in children before a vaccine was rolled out across the world in the 1980s.
As reported in the journal Genome Biology, researchers isolated the genome of HiB from the tooth of a 6-year-old boy who died from around 540 to 550 CE and was buried at the Anglo-Saxon cemetery of Edix Hill in England. Along with detecting HiB on the boy's dental calculus, they also found the dreaded bacteria responsible for the plague, Yersinia pestis, which likely killed him.
“This is the second case of plague co-infection in archeological samples reported recently,” the study authors write in their paper. “The site of Edix Hill, which has yielded multiple plague genomes, illustrates how plague affected whole populations already afflicted by other diseases and might have been the final blow for already immunocompromised individuals.”
H. influenzae was first described in 1892 by German scientist Richard Pfeiffer. He isolated the bacteria from the noses of patients during an influenza pandemic, leading him to suspect it was a causative microbe of the flu. His estimation turned out to be wrong (we know now influenza is caused by a virus) but the misleading name for the germ given by Pfeiffer stuck around.
HiB happily lives in people’s nose and throat, usually causing no harm, but the infection can be dangerous for young children who do not have protective antibodies against the bug. In unvaccinated children, the bacteria can produce nasty bloodstream infections, pneumonia, and meningitis. Fortunately, the HiB vaccine is highly effective and, as a direct result, the number of cases has dropped dramatically in just a few decades, although certain parts of the world have seen rising cases in recent years due to vaccine hesitancy.
This latest discovery is already shedding some light on the little-known evolutionary history of HiB. Prior to this new research, the earliest genome of H. influenzae was from a sample taken in 1940. Curiously, the genome of the bacteria taken from the Anglo-Saxon boy appears to be remarkably similar to the 20th-century sample, suggesting the bacteria primarily reproduced through cloning and has remained largely unchanged for centuries.
“We can see that our Anglo-Saxon genome is genomically similar to another Hib-II genome of the 1940s, from which we conclude that evolutionary dynamics of this clade probably remained mostly clonal since the sixth century CE,” the study authors concluded.