Rats are notorious for spreading the plague, but there are many other diseases which they also are they are also known to spread. In fact the number is in the region of 35 different maladies transmitted in their urine, saliva and faeces. The plague is famous for being one of the most deadly diseases of all time. The biggest outbreak was the Black Death in mediaeval times. This led to the death of hundreds of millions of people, including a third of the population of Europe at the time.

There are several reasons why so many people died. This includes the fact that there was no effective treatment available at the time. Other factors include poor understanding of the transmission of disease at the time. Living conditions were cramped and squalid in many of the urban areas of Britain during that period of history. Multiple occupancy was a serious problem with many people in one room and several people sharing a bed. Modern antibiotics are effective at killing the bacteria Yersinia pestis which causes the disease.

The mortality rate without antibiotic treatment is 100%. The people at the time of the Black Death were desperate for a cure. They strapped live toads, chickens and other animals to the swollen nodes at the tops of their legs. These lumps are known as buboes. The idea was that the animals would draw the badness from the lumps, hastening recovery. It is likely that the warmth from the animals' bodies led to increased inflammation and bursting of the nodes. This is likely to have sped the demise of the individual through septicaemia, rather than hastening their recovery.

Recently scientists have found that the feathers of chickens contain an unusual substance. It was found to inhibit the growth of Yersinia pestis. There may have been some truth in their application of this unusual treatment.

The plague spread throughout Europe like wildfire, introduced via the city of Caffa. This was held under siege by the Mongol army for a prolonged period of time. They attempted to take the walled city by infecting the inhabitants. They did this by catapulting the infected army's corpses over the battlements and into the city. Many of the inhabitants of the city fled north into Europe, taking the terrible disease with them.

Recent evidence discovered by scientists indicates that the rat may not have been to blame for the spread. It may in fact have been a another rodent species. The discovery was made due to the mismatch of the timing of the peaks in disease activity with peaks in the rat population.

The disease is transmitted from fleas to a new host because the bacteria causes a blockage in the flea's intestines. This causes it to regurgitate it's meal. When it takes blood into its abdomen from its next victim, it becomes infected before vomiting it back up into the new host.

Doctors at the time would wear head to toe coverings with boots, long robes and a mask and hood covering the head. They would put sweet smelling herbs in the nose, as it was considered that the disease is transmitted through smell. They may have been defending themselves against fleabites and stopping themselves getting the disease. This wasn't in the way they thought.

Dr Toby Bateson for HammerTechLtd.com