Buboes and bubonic plague

The designation of bubonic plague arises from the fact that it is the only disease where buboes are a normal clinical feature. This unique feature has a unique causation. The skin is the human body’s first line of defence against infection. Bubonic plague is transmitted by blocked rat fleas, which pierce the skin and, attempting to feed, often regurgitate a lethal dose of plague bacteria and release it at an intradermal level in the catchment area of the lymphatic system. In most cases, the regurgitant will be drained from the bite site through a lymphatic tract to a lymph node that, upon infection by plague bacteria, begins to swell and develop into an intensely painful bubo.

For these reasons, buboes mainly arise in anatomical locations with concentrations of lymph nodes, the groin and adjacent part of the thigh (inguinal–femoral area), the armpits (axillas) and the neck (cervix). This is corroborated by a huge amount of clinical descriptions in historical sources; modern and historical specifications of the usual sites of plague buboes are identical. Because the legs are the largest surface area of human beings and because legs can attract fleas both when people are asleep and standing up or walking about, most bites occur there. The contagion will then usually be drained to a lymph node in the inguinal–femoral area. Sleeping humans will often be bitten on the upper parts of the body and develop buboes in the armpits or quite frequently on the neck or nearby shoulder.

The specificity of transmission of infective bacterial loads of plague bacteria can explain that bubonic plague is the only epidemic disease clinically characterized by the clinical manifestation of buboes and is, therefore, also a defining feature. The designation bubonic plague is appropriate and contains an identifying function.

The infection of a lymph node is characterized by excruciating pain from the moment it begins to swell and before a bubo appears, which usually is on the second or third day.