Pneumonic plague in the context of "Black Death"

Population figures for the Indigenous peoples of the Americas before European colonization have been difficult to establish. Estimates have varied widely from as low as 8 million to as many as 100 million, though by the end of the 20th Century, many scholars gravitated toward an estimate of around 50 million people.

The monarchs of the nascent Spanish Empire decided to fund Christopher Columbus' voyage in 1492, leading to the establishment of colonies and marking the beginning of the migration of millions of Europeans and Africans to the Americas. While the population of European settlers, primarily from Spain, Portugal, France, England, and the Netherlands, along with African slaves, grew steadily, the Indigenous population plummeted. There are numerous reasons for the population decline, including exposure to Eurasian diseases such as influenza, pneumonic plagues, and smallpox; direct violence by settlers and their allies through war and forced removal; and the general disruption of societies. Scholarly disputes remain over the degree to which each factor contributed or should be emphasized; some modern scholars have categorized it as a genocide, claiming that deliberate, systematic actions by Europeans were the primary cause. Traditional interpretation of the decline by scholars have disputed this characterization, maintaining that incidental disease exposure was the primary cause. This is supported by evidence where 50-80 percent of the population died from waves of diseases caused by Europeans in places such as Mexico in the 16th century.

Bubonic plague is one of three types of plague caused by the bacterium Yersinia pestis. One to seven days after exposure to the bacteria, flu-like symptoms develop. These symptoms include fever, headaches, and vomiting, as well as swollen and painful lymph nodes occurring in the area closest to where the bacteria entered the skin. Acral necrosis, the dark discoloration of skin, is another symptom. Occasionally, swollen lymph nodes, known as "buboes", may break open.

The three types of plague are the result of the route of infection: bubonic plague, septicemic plague, and pneumonic plague. Bubonic plague is mainly spread by infected fleas from small animals. It may also result from exposure to the body fluids from a dead plague-infected animal. Mammals such as rabbits, hares, and some cat species are susceptible to bubonic plague, and typically die upon contraction. In the bubonic form of plague, the bacteria enter through the skin through a flea bite and travel via the lymphatic vessels to a lymph node, causing it to swell. Diagnosis is made by finding the bacteria in the blood, sputum, or fluid from lymph nodes.

Yersinia pestis (Y. pestis; formerly Pasteurella pestis) is a gram-negative, non-motile, coccobacillus bacterium without spores. It is related to pathogens Yersinia enterocolitica, and Yersinia pseudotuberculosis, from which it evolved. Yersinia pestis is responsible for the disease plague, which caused the Plague of Justinian and the Black Death, one of the deadliest pandemics in recorded history. Plague takes three main forms: pneumonic, septicemic, and bubonic. Y. pestis is a facultative anaerobic parasitic bacterium that can infect humans primarily via its host the Oriental rat flea (Xenopsylla cheopis), but also through aerosols and airborne droplets for its pneumonic form. As a parasite of its host, the rat flea, which is also a parasite of rats, Y. pestis is a hyperparasite.

Y. pestis was discovered in 1894 by Alexandre Yersin, a Swiss/French physician and bacteriologist from the Pasteur Institute, during an epidemic of the plague in Hong Kong. Yersin was a member of the Pasteur school of thought. Kitasato Shibasaburō, a Japanese bacteriologist who practised Koch's methodology, was also engaged at the time in finding the causative agent of the plague. However, Yersin actually linked plague with a bacillus, initially named Pasteurella pestis; it was renamed Yersinia pestis in 1944.

Plague is an infectious disease caused by the bacterium Yersinia pestis. Symptoms include fever, weakness, headache and black lips. Usually this begins one to seven days after exposure. There are three forms of plague, each affecting a different part of the body and causing associated symptoms. Pneumonic plague infects the lungs, causing shortness of breath, coughing and chest pain; bubonic plague affects the lymph nodes, making them swell; and septicemic plague infects the blood and can cause tissues to turn black and die.

The bubonic and septicemic forms are generally spread by flea bites or handling an infected animal, whereas pneumonic plague is generally spread between people through the air via infectious droplets. Diagnosis is typically made by finding the bacterium in fluid from a lymph node, blood or sputum.

Septicemic plague is one of the three forms of plague, and is caused by Yersinia pestis, a gram-negative species of bacterium. Septicemic plague is a systemic disease involving infection of the blood and is most commonly spread by bites from infected fleas. Septicemic plague can cause disseminated intravascular coagulation and is always fatal when untreated. The other varieties of the plague are bubonic plague and pneumonic plague.

The Great Plague of London, lasting from 1665 to 1666, was the most recent major epidemic of the bubonic plague to occur in England. It happened within the centuries-long Second Pandemic, a period of intermittent bubonic plague epidemics that originated in Central Asia in 1331 (the first year of the Black Death), and included related diseases such as pneumonic plague and septicemic plague, which lasted until 1750.

The Great Plague killed an estimated 100,000 people—almost a quarter of London's population—in 18 months. The plague was caused by the Yersinia pestis bacterium, which is usually transmitted to a human by the bite of a flea or louse.