How Did the Black Death Spread: The Cause and Spread of the Black Death

**Bubonic Plague
**

The Black Death - also known as the bubonic plague - was a disease that devastated Medieval Europe like no other. Between 1346 and 1352 it killed 45 million people, wiping out a third of Europe’s population. Even today just mentioning the word “black death” or “black plague” sends shudders of horror through adults and children alike and reflects on the plague’s swiftness and terrible ferocity in how it killed its victims.

If you got the disease, egg-shaped painful swellings called buboes would develop underneath your skin in the groin, armpits and neck accompanied by symptoms of fever, chills, and nausea. Death came within a week. A mutated version of the disease - pneumonic plague- attacked the respiratory system and your lungs would drown in their own pus and blood.

Septicemic plague, a rarer form of the disease from which the"black death" got its name, invaded your bloodstream, causing massive damage to your heart and vital organs. Limbs deprived of nutrients and oxygen turned a gangrenous black and your insides would turn to jello from massive hemorrhaging. For both these forms of the disease, death came within hours.

Disease Causes

Back then, people thought the plague was caused by bad air, an imbalance of the body humors or was a terrible punishment inflicted by God. The disease spared noone, attacking both rich and poor with no end in sight. It wasn’t until the 17th century that revealed the plague’s true cause, Yersenia pestis, a rod shaped bacterium that is transmitted to humans by fleas from infected rats.

The bacterium is named for Alexandre Yersin, the Swiss biologist who isolated it in 1894 when a third pandemic of the plague struck India and China. Soon after, scientists Paul-Louis Simond of France and Masanori Ogata of Japan discovered the two main carriers that transmit Y. pestis to humans: the oriental flea (X.chopis) and the common black rat (R.rattus) and were able to prove the connection between sick rats and diseased humans.

Disease Pathway

The oriental flea sucks the blood from an infected rat. The bacterium walls off an area in the flea’s digestive tract preventing the flea from digesting its blood meal. When the rat sucumbs to the plague, the starving flea leaves its furry host to find a meal in humans instead. When the flea bites into human flesh it regurgitates Y. pestis into the open wound transmitting it to its human host..

How the Plague Spread

Most historians think the source for bubonic plague originated in the remote grasslands of Centra Asia . Wild rodents there infected with Y. pestis (along with their flea parasites) migrated to nearby villages after some natural disaster disturbed their food supply. They eventually spread the bacterium to colonies of black rats living in more established cities and towns.

The first known plague pandemic occurred in Egypt in 541 during Emperor Justinian’s rule and is said to have helped bring down the Byzantine Empire. No one knows how many died but early writings account the dead were so numerous they had to be thrown in mass graves. By the late 1330s it trickled out of Central Asia and headed east to China via the Silk Road trade route. Plague carrying rats stowed away on ships headed for Europe infecting crew members whom spread the illness to families and communities in the Italian port cities of Genoa and Florence. The sick rats fled the ships and infected city rodent populations. By 1346 the second pandemic of the plague had begun.

How people lived contributed to the plague’s spread. The mud and twig roofs in peasants homes made an ideal nesting area for rats . People shared living quarters with their animals which provided more hosts for fleas. Regular bathing or laundering of bedding or clothing was uncustomary so fleas thrived on the body and in one’s personal belongings.

Early efforts to contain the plague by quarantining the sick and burning the dead proved ineffective. Some people became shut-ins hoping to outlast the plague while others fled infected villages in an attempt to outrun it. Infection from the plague meant a sure and swift death with no hope for treatment in sight

The Plague Today

Bubonic plague still occurs in parts of Asia and Africa today but is highly treatable with antibiotics. The World Health Organization reports an average of 1,500 plague cases occur worldwide each year.

References: The Black Death, Slavicek, L.C., Infobase Publishing, 2008