The most popular theory regarding the rapid spread of the plague during the Black Death involves plague carrying rats. However, the latest findings from London indicate that rats may have been unjustly blamed.

The Black Death is considered to be one of the worse pandemics in the entirety of human history. The pandemic was caused by the spread of a bacterium known as Yersinia pestis. This bacterium is known to cause several types of plagues. Many experts believe that the plague came from Asia and was spread to Europe through the Silk Road. It is also widely believed that the spread of the plague was caused by flea infested rats. However, new investigations on the matter have shown that this may not have been the case.

A team of forensic scientists and archeologists studied a group of 25 skeletons found in London. The skeletons were unearthed during a Crossrail construction project in the Charterhouse Square in Farringdon and further studies have shown that the remains belonged to plague victims.

"Analysis of the Crossrail find has revealed an extraordinary amount of information allowing us to solve a 660 year mystery," said Jay Carver, the lead archeologist of Crossrail. "This discovery is a hugely important step forward in documenting and understanding Europe's most devastating pandemic."

The site where the skeletons were found is believed to be the second "Black Death emergency" burial ground during the mid-1300s. Upon closer inspection, the scientists were able to extract Yersinia DNA from the teeth of the victims. Obtaining the DNA proved the scientists suspicions that the victims died of the bubonic plague.

"Historical sources told us that thousands of burials of Black Death victims were made in the 14th Century in the area that is now modern day Farringdon, but until Crossrail's discovery, archaeologists had been unable to confirm the story," Carver added. "Ancient DNA work is complex and still in development but the results do confirm the presence of the deadly plague bacterium preserved in the teeth."

The researchers say that the sheer speed at which the bubonic plague spread could only mean that the infection was airborne. Their findings may overturn the rat flea theory, which is widely considered as the cause of the Black Death.

Public health experts are now considering the possibility that the infection may have been spread by coughs and sneezes of people already infected by the plague. If the new theory is proven to be correct, then the term "bubonic plague" would no longer apply to the disease that brought about the Black Death. Since it was spread via the lungs, the proper term would be "pneumonic plague."

"The skeletons discovered at Crossrail's Farringdon site provide a rare opportunity for us to study the medieval population of London that experienced the Black Death," said Dan Walker, an osteologist who worked with Crossrail on the study. "We can start to answer questions like: where did they come from and what were their lives like? What's more, it allows for detailed analysis of the pathogen, helping to characterise the history and evolution of this devastating pandemic."