Scientists have achieved a breakthrough in understanding the history of human viral infections, successfully reconstructing the genome of a cold virus that infected a woman in London approximately 250 years ago. This remarkable feat represents the oldest confirmed example of a human RNA virus identified to date, offering a unique window into the evolution of respiratory illnesses. The discovery highlights the potential of historical medical collections as untapped archives of past pathogens.
Recovering genetic material from ancient viruses is challenging, particularly for RNA viruses. Unlike DNA, RNA is inherently unstable and degrades rapidly after death, typically within hours. This new research demonstrates that RNA can survive, albeit in fragmented form, within preserved human tissue for centuries, opening up exciting possibilities for studying past epidemics and viral evolution. The findings, published as a preprint on BioRxiv, suggest that museum and pathology collections hold a wealth of information about the history of infectious diseases.
Unlocking the Past Through Preserved Tissue
Researchers have previously recovered viral traces from ancient human remains, but these successes largely involved DNA viruses, which are more resilient. The team, led by Erin Barnett at the Fred Hutchinson Cancer Center, deliberately sought to overcome the limitations of studying ancient RNA. They focused on pathology collections, where tissues have been preserved for decades or even centuries. A key factor in their success was the preservation method used for the samples. Rather than the standard formalin preservation used since the early 1900s, the lung tissue samples analyzed were preserved in alcohol, which offered a better chance of RNA survival.
The samples originated from the Hunterian Anatomy Museum at the University of Glasgow, specifically lung tissue from two individuals: a woman from London who died around the 1770s, and another person who died in 1877, whose sex is currently unknown. Both individuals had documented histories of severe respiratory illness, making them ideal candidates for this research.
Reconstructing a 250-Year-Old Viral Genome
Extracting and analyzing the RNA proved to be a complex process. The recovered RNA was heavily fragmented, with most pieces measuring only 20 to 30 nucleotides in length – a tiny fraction of the size of a complete RNA molecule, which can exceed 1,000 nucleotides. Despite this challenge, the researchers painstakingly pieced together the fragments, ultimately reconstructing the full RNA genome of a rhinovirus, a common cause of the common cold.
Further analysis revealed that the woman also had bacterial infections, including Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis, suggesting a complex and potentially dangerous combination of pathogens affecting her lungs. This highlights that what might appear as a simple “cold” could have been a far more serious illness in the past.
A Lost Lineage of Rhinovirus
Comparing the reconstructed viral genome to a vast database of viral sequences maintained by the U.S. National Institutes of Health, researchers determined that the historical virus belonged to the human rhinovirus A group. Interestingly, this particular viral lineage appears to be extinct today. The closest modern relative identified was a genotype known as A19, with an estimated common ancestor dating back to the 1600s. This suggests the virus found in the woman’s lungs represents a long-lost branch on the rhinovirus family tree.
The researchers emphasize the importance of acknowledging the individuals whose tissues were used in this study, recognizing them beyond their status as anonymous specimens. Recovering this biological information, they argue, helps restore visibility to stories that would otherwise be lost to time.
Implications for Future Research
Experts in the field, such as Love Dalén at Stockholm University, have hailed the study as a significant step forward. Dalén noted that the success in recovering RNA from “wet” medical collections – those preserved without formalin – opens up new avenues for research. He suggests this is just the beginning of a larger expansion in ancient RNA virus research, as many RNA viruses evolve rapidly, studying them across centuries could provide valuable insights into viral evolution that modern samples alone cannot offer.
This research shifts the focus from relying on exceptionally preserved samples, like those found in permafrost, to utilizing more readily available historical collections. This approach suggests that museums and pathology archives may contain a hidden record of past outbreaks, preserved not only in DNA but also in RNA. Tracking how respiratory viruses evolved and moved through populations, and understanding their changing relationships with other infections, may now be within reach.
The reconstruction of this 18th-century cold virus is more than just a historical curiosity; it’s a testament to the power of innovative techniques and the potential for unlocking a deeper understanding of our shared past with infectious diseases. Further research utilizing these methods promises to reveal even more about the evolution of viruses and their impact on human health.
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Disclaimer: This article provides informational content and should not be considered medical advice. Always consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.
