Plague produces dramatic visible changes on the body, and those changes depend on which of the three forms of the disease a person develops. The most recognizable sign is a bubo: a massively swollen, painful lymph node that can swell to the size of a chicken egg. But plague can also cause skin to turn black, bleeding under the skin, and bloody sputum from the lungs. Here’s what each form actually looks like.
Bubonic Plague: Swollen Lymph Nodes
Bubonic plague is the most common form, accounting for the majority of cases worldwide. It begins after a flea bite, with an incubation period of 2 to 8 days before symptoms appear. The hallmark is the bubo, a lymph node so swollen and inflamed that it becomes visibly prominent under the skin. Buboes typically appear in the groin, armpit, or neck, whichever lymph node is closest to the site of the flea bite.
A plague bubo looks nothing like a normally swollen lymph node from a cold or minor infection. It’s significantly larger, often reaching 1 to 10 centimeters, and the overlying skin becomes taut, reddened, and warm to the touch. The swelling is extremely tender. In some cases the skin over the bubo takes on a purplish hue as the tissue beneath becomes increasingly inflamed and blood-engorged. The bubo can eventually rupture and drain pus if left untreated. Along with the bubo itself, patients look visibly ill with high fever, chills, and obvious exhaustion.
Septicemic Plague: Blackened Skin
Septicemic plague is what gave the disease its medieval nickname, the Black Death. This form occurs when the bacteria enter the bloodstream directly or when bubonic plague progresses without treatment. The key difference from bubonic plague is that there’s no bubo. Instead, the infection is systemic from the start, which makes it harder to recognize visually in the early stages.
As septicemic plague advances, the most striking visible change is the skin. Tiny blood vessels throughout the body begin to leak or clot, causing purplish-black patches of bleeding under the skin called purpura. These can appear anywhere on the body but are especially noticeable on the extremities. Fingers, toes, the nose, and ears can turn black as tissue dies from lack of blood flow. This gangrene is the signature look of septicemic plague, and it’s what people typically picture when they think of plague’s appearance. The blackened tissue is actual dead skin and muscle, not just discoloration, and in severe cases entire hands or feet can be affected.
Without treatment, about half of people with septicemic plague die from septic shock within 3 to 6 days of symptom onset. The case fatality rate for septicemic plague sits around 50%, higher than bubonic plague, largely because the absence of a visible bubo delays correct diagnosis.
Pneumonic Plague: Bloody Cough
Pneumonic plague attacks the lungs and is the most dangerous form. It can develop as a complication of bubonic or septicemic plague, or a person can contract it directly by inhaling respiratory droplets from an infected person or animal. This is the only form of plague that spreads person to person.
Visually, pneumonic plague looks different from the other two forms. There are no buboes and, at least initially, no skin discoloration. What you see instead is a rapidly deteriorating respiratory illness. Patients develop a severe cough that produces watery or blood-tinged sputum, sometimes frothy and pink, sometimes frankly bloody. Breathing becomes labored, the face may appear flushed or cyanotic (bluish from oxygen deprivation), and the person deteriorates quickly. Pneumonic plague is fatal in virtually all cases unless antibiotic treatment begins within the first day of symptoms.
How Quickly These Signs Appear
Timing varies by form. Bubonic plague has the longest runway: after a flea bite, it takes 2 to 8 days before the bubo and fever develop. During that incubation window, the person may feel fine or have only vague malaise. Once the bubo appears, it grows rapidly over the next day or two.
Septicemic plague can develop alongside bubonic plague or on its own, and the skin changes from bleeding and gangrene tend to appear as the infection overwhelms the bloodstream, typically a few days into the illness. Pneumonic plague progresses the fastest. The cough, chest pain, and bloody sputum can escalate to respiratory failure within 2 to 4 days if untreated.
Where Plague Still Occurs
Plague is not a purely historical disease. It exists on every continent except Oceania, and the three countries reporting the most cases are the Democratic Republic of Congo, Madagascar, and Peru. The United States still sees a handful of cases each year, mostly in rural areas of the Southwest where wild rodents carry the bacteria. Globally, more than 21,000 people were affected in the first decade of the 2000s, with an overall case fatality rate of 7.4%, a figure that reflects the fact that most treated cases survive. Modern antibiotics are highly effective when given early, but the disease remains deadly when diagnosis is delayed or treatment isn’t available.
Plague vs. Other Swollen Lymph Nodes
Many infections cause swollen lymph nodes, so it’s worth understanding what sets a plague bubo apart. Ordinary lymph node swelling from a throat infection or skin wound is usually modest, perhaps a centimeter or so, mildly tender, and moves freely under the skin. A plague bubo is dramatically larger, exquisitely painful, and often fixed in place because the surrounding tissue is inflamed and matted together. The overlying skin is red or dusky, and the patient is severely ill with high fever, not just mildly uncomfortable. The combination of an intensely painful, rapidly enlarging lymph node with a high fever and a history of possible flea or rodent exposure is what distinguishes plague from routine causes of swollen glands.