Bubonic plague

Of all the insect diseases, Bubonic plague has had the most profound effect on modern human history. Bubonic plague, caused by the bacterium, Yersinia pestis, is back in the news. According to a recent report in Nature Genetics DNA sequencing of Yersinia pestis samples from around the world places the origin of the strains in China about 2600 years ago.

An especially virulent form of Bubonic plague spread throughout Europe in the 1300s and killed an estimated half of the European population. The plague is carried by the Oriental rat flea, Xenopsylla cheopis. Rats carrying the plague may appear asymptomatic until shortly before death. The fleas abandon the dying rats and bite humans and other potential hosts. The rat fleas are the primary vector moving the bacterium from the rat to humans.

During the 1300s, little was understood about microorganisms and disease. Certainly, the disease was not associated with rats or rat fleas. Lacking the basic biological information, European society lacked the knowledge that could have controlled the spread of the plague and minimized its affects.

Today, there are other microbe capable of causing modern pandemics. Some are vectored by insects and some are transmitted by human interactions. Our store of scientific knowledge, understanding of the diseases and their vectors is important in preventing plagues in our modern era.