Even in 2021, bubonic plague continues to exist in nature, and there are generally a few thousand human cases per year. Going back to the beginning of the 20th century, it is estimated that there were roughly one million cases per year in 1907. Within two decades, this number had fallen below one fifth of this level to 170,000 cases per year in the 1920s, and in the 1940s it was just over 20,000 per year. By the mid-20th century, it had fallen below 5,000 cases per year, but the rapid decrease in cases observed in the first half of the 1900s did not continue through the second half of the century. Even in 2019, there was one case of plague recorded in the United States. How infection occurs Yersinia pestis is the bacteria that causes the plague virus, and it is most commonly spread by rats and their fleas. The disease survives by fleas infecting rats, which in turn infect other fleas; the majority of rats survive the disease, which facilitates its spread; this is known as the "enzootic cycle ". Interestingly, the disease is usually fatal for the fleas, as it blocks their "stomachs" and causes them to starve; as the fleas get hungrier, they attempt to feed on more hosts, spreading the disease more rapidly. When the rats die, the parasitic fleas then search for a new host, which means that other animals (particularly mammals) are susceptible to this virus. While rat fleas can not survive on other hosts for very long, they can infect other (including human) fleas with the virus. The most common way for humans to contract the plague however, is when a rat flea bites its human host; during this process the flea simultaneously regurgitates Yersinia pestis bacteria into the wound, and this causes bubonic plague. Humans can then spread the disease among one another by coming into contact with the infected tissue or fluids of an infected person, or from the transfer of fleas. Continued existence of the plague Plague is extremely difficult to eradicate in nature, as rodent communities in the wild provide natural reservoirs for the disease to spread. In previous centuries, rats had much more frequent contact with humans for a variety of reasons; houses were more often made of wood (which made infestations easier), public spaces were much dirtier, and the presence of rats was tolerated more. As the understanding of epidemiology grew in the 20th century, this greatly reduced the frequency of plague in human populations. Unlike human diseases such as smallpox, which was eradicated through vaccination and other medical advancements, basic sanitation and the extermination of rats have been the driving force behind the decline of plague.

The Third Plague Epidemic began in the mid-1800s in Yunnan, China, (an area that is still a natural reservoir for the Yersinia pestis bacteria) and had a huge death toll across Asia in the next century. While plague was confined to the Yunnan region for some decades, the mass displacement and social upheaval caused by the Taiping Rebellion saw millions flee the area , bringing the disease to other parts of the country. A plague epidemic then emerged in British-controlled Hong Kong in 1894, where merchants then unknowingly transported infected rats to other parts of the empire along various trade routes. Arrival in Bombay The first Indian cases were reported in Bombay (present-day Mumbai), and the Bombay Presidency suffered more losses than any other region in India (although there were some individual years where the state of Punjab reported more deaths). As with most disease or famine outbreaks in the region, the British authorities were slow to react, and their eventual response was in many ways too late. In some cases authorities even facilitated the spread of the disease; with multiple accounts of the military forcing healthy people into quarantine camps, evicting and burning homes of the afflicted, or by using such excessive force that the public would refuse medical help. Spread in India Lack of understanding among the Indian public was also to their own detriment. Some religions in India forbid the killing of rats, while some people simply refused to acknowledge that they were sick. As the plague in Bombay spiraled out of control, many fled to other parts of the country, taking the plague with them. It is estimated that there were over one million deaths in India by 1902, and almost one million further deaths in 1903 alone. The first four months of 1904 also saw over half a million deaths, almost matching the entire total for 1902. Plague would remain endemic to India for the next few decades, and there are varying reports of up to 10 or 12 million total plague deaths in this time. The public health measures taken to combat the plague in the early 20th century would mark the beginnings of India's public health system, and some of the quarantine measures put in place by the colonial government were even used in 2020 during the outbreak of the COVID-19 pandemic.

Details of the location of bubonic plague infections in Sydney by place of residence

The plague outbreak in Bombay around the turn of the twentieth century was the most fatal plague epidemic documented in any city in the past 130 years. Between September 1896 and May 1897, the Municipal Hospital of Bombay reported a fatality rate in plague cases of 61.5 percent. The fatality rate among plague cases ranged between 38 and 82 percent in different months, was highest in the winter. The reason for the peak in February in Bombay is because the temperatures and climate in these months provide the optimal conditions for the breeding of rats and fleas; in contrast to this, earlier epidemics in Europe typically peaked in Autumn, whereas the epidemics in Hong Kong between 1894 and 1902 were hardest felt in May or June.

Plague, caused by Yersinia pestis, was classified as a reemerging infectious disease by the World Health Organization. The five human pneumonic plague cases in Yulong County in 2005 gave rise to the discovery of a Yulong plague focus in Yunnan province, China. Thereafter, continuous wild rodent plague (sylvatic plague) was identified as the main plague reservoir of this focus. In this study, the epizootics in Yulong focus were described, and three molecular typing methods, including the different region (DFR) analysis, clustered regularly interspaced short palindromic repeats (CRISPRs), and the multiple-locus variable number of tandem repeats (VNTR) analysis (MLVA) (14+12), were used for the molecular typing and source tracing of Y. pestis isolates in the Yulong plague focus. Simultaneously, several isolates from the vicinity of Yunnan were used as controls. The results showed that during the 10-year period from 2006 to 2016, an animal plague epidemic occurred in 6 of those years, and 5 villages underwent an animal plague epidemic within a 30-km2 area of the Yulong plague focus. Searching for dead mice was the most effective monitoring method in this plague focus. No positive sample has been found in 6937 captured live rodents thus far, suggesting that the virulence of strains in the Yulong plague focus is stronger and the survival time of mice is shorter after infection. Strains from Lijiang, Sichuan and Tibet were of the same complex based on a typing analysis of DFR and CRISPR. The genetic relationship of Y. pestis illustrated by MLVA “14+12” demonstrates that Tibet and Sichuan strains evolved from the strains 1.IN2 (Qinghai, 1970 and Tibet, 1976), and Lijiang strains are closer to Batang strains (Batang County in Sichuan province, 2011, Himalaya marmot plague foci) in terms of genetic or phylogenic relationships. In conclusion, we have a deeper understanding of this new plague focus throughout this study, which provides a basis for effective prevention and control.

Although the Black Death peaked in Europe between 1348 and 1351, plague was almost always present in Britain for the next four centuries. In most years, plague was a dormant threat that affected very few people, and diseases such as smallpox and influenza were much more widespread; however, bubonic plague was prone to outbreaks that could decimate populations in a few short years. In London, plague outbreaks occurred every few decades, usually with death tolls in the tens of thousands. The duration and severity of these epidemics varied, sometimes having high death tolls but subsiding quickly, while others had relatively lower death tolls but could last for a number of years. As London's population and density also grew drastically during this period, plague affected the city differently in the sixteenth and seventeenth centuries. Great Plague of London The final major plague epidemic observed in Britain took place in 1665 and 1666. It became known as the "Great Plague" as it was the last of its kind in Britain, and its death toll eclipsed all other epidemics in the preceding century (although it was much smaller than that of the Black Death). The plague lasted for eighteen months, and had a reported death toll of more than 70,000 in this time; although modern historians estimate that the actual death toll exceeded 100,000. At its peak in September 1665, it is reported that there were more than 7,000 deaths per week, although this may have also been much higher due to the limited records kept at the time. Another reason for the lack of accurate records relating to this epidemic is because of the Great Fire of London in 1666. The fire started on September 02. 1666, and destroyed almost all of the city within the walls, leaving thousands homeless. Historians continue to debate the fire's significance, some citing that it destroyed the unsanitary dwellings where infected rats lived and drove them from the city, while others claim that the timings were purely coincidental and that the epidemic had already begun to subside in February.

Details of the location of bubonic plague infections in Sydney by place of work

BackgroundPlague is an epidemic-prone disease with a potential impact on public health, international trade, and tourism. It may emerge and re-emerge after decades of epidemiological silence. Today, in Latin America, human cases and foci are present in Bolivia, Brazil, Ecuador, and Peru.AimsThe objective of this study is to identify where cases of human plague still persist in Latin America and map areas that may be at risk for emergence or re-emergence. This analysis will provide evidence-based information for countries to prioritize areas for intervention.MethodsEvidence of the presence of plague was demonstrated using existing official information from WHO, PAHO, and Ministries of Health. A geo-referenced database was created to map the historical presence of plague by country between the first registered case in 1899 and 2012. Areas where plague still persists were mapped at the second level of the political/administrative divisions (counties). Selected demographic, socioeconomic, and environmental variables were described.ResultsPlague was found to be present for one or more years in 14 out of 25 countries in Latin America (1899–2012). Foci persisted in six countries, two of which have no report of current cases. There is evidence that human cases of plague still persist in 18 counties. Demographic and poverty patterns were observed in 11/18 counties. Four types of biomes are most commonly found. 12/18 have an average altitude higher than 1,300 meters above sea level.DiscussionEven though human plague cases are very localized, the risk is present, and unexpected outbreaks could occur. Countries need to make the final push to eliminate plague as a public health problem for the Americas. A further disaggregated risk evaluation is recommended, including identification of foci and possible interactions among areas where plague could emerge or re-emerge. A closer geographical approach and environmental characterization are suggested.

The effect of parameters (X latitude and Y longitude: GPS localization of the sampling place; IRS: Indoor Residual Spraying which represent the number of insecticide interventions the population should underwent (Max: 1 per year) on KD50, KD90 and 24 hours survival rate of Xenopsylla cheopis.

Details of the location of bubonic plague infections in Sydney

The market for Plague Therapeutics is projected to grow exponentially, driven by the rising incidence of plague cases in various regions and the increasing demand for effective treatments. The market is expected to be valued at USD X million in 2025, with a CAGR of XX% during the forecast period of 2025-2033. Key factors propelling market growth include the increasing awareness of the disease, advancements in vaccine development, and the growing focus on improving patient outcomes. The market is segmented based on application (hospital pharmacies, retail pharmacies, and others) and type (vaccine and drugs). The vaccine segment currently dominates the market, owing to the effectiveness of vaccines in preventing plague infections. However, the drugs segment is expected to witness significant growth in the coming years due to the increasing demand for antibiotics and other treatments to combat the disease. Geographically, North America is the largest market for Plague Therapeutics, followed by Europe and Asia-Pacific. The rising incidence of plague cases in Africa and the Middle East is expected to contribute to the growth of the market in these regions.

Mortality values of Xenopsylla cheopis populations to Deltamethrin in Madagascar.

Bubonic plague was a constant threat to Afro-Eurasian populations during the Second Plague pandemic. This pandemic arrived in Europe as the Black death in 1347, and although it never became endemic, it was constantly re-introduced to the continent over the next four centuries. By the late seventeenth century, most regions of Europe had recorded their final epidemics (but not necessarily the final cases), and it eventually subsided in the mid-nineteenth century. The death tolls due to plague were relatively low in most years, however, when epidemics appeared they could often decimate populations within a few short years, and lead to mass evacuations of major cities (such as in London in 1665). Plague in Russia Of the sample epidemics shown here, the two largest cases were in Russia; a region where plague outbreaks were much more frequent than in other parts of Europe. The reason for this was because plague would spread along the Volga river, after being brought to the Caspian Sea by fishermen from the Eurasian Steppes (where the plague bacteria Yersinia pestis is thought to originate). Between these two epidemics, it is estimated that Russia lost over half a million people. The epidemic of 1709, which spread across Northern Europe during the Great Northern War, saw a reported 150,000 deaths across the Russian Empire. The plague epidemic of 1771 in Russia saw the deaths of approximately 60,000 in the capital city, and as many as 300,000 in the surrounding region. In Moscow, the government's attempts to contain the outbreak resulted in a riot by the citizens, and the aftermath saw significant socio-political upheaval in the city and beyond.

This volume is a chronological record, by date of report of every case of plague known to the authorities during the period.

Information included is date of notification, name, age, where found, place of employment or school, when last employed, notifying doctor, staff medical officer, diagnosis, date of attack, date of inoculation (if done), date of removal, whether the patient died or recovered and date, number of residents in house and number sent to quarantine, number inoculated, occupation of patient, subsequent cases and remarks (usually about tests, contacts, etc).

After the 1902 outbreak got under way the items of information in the above list after ''date of attack'' are generally omitted except in cases of death. In the 1900 section additional information is shown: 'Probable place of infection', 'Place of infection undetermined' and 'Premises where dead rats were discovered'.

Collected data for plague cases in Europe from the Public Health Reports (formerly Bulletins of the Public Health and Weekly Abstract of Sanitary Reports) between 1879-1950.

Correlations results between the mortality values parameters and between the times spent by fleas in the insectariums (Pearson's correlation Test).

BackgroundPlague, a zoonosis caused by Yersinia pestis, is found in Asia and the Americas, but predominantly in Africa, with the island of Madagascar reporting almost one third of human cases worldwide. Plague's occurrence is affected by local climate factors which in turn are influenced by large-scale climate phenomena such as the El Niño Southern Oscillation (ENSO). The effects of ENSO on regional climate are often enhanced or reduced by a second large-scale climate phenomenon, the Indian Ocean Dipole (IOD). It is known that ENSO and the IOD interact as drivers of disease. Yet the impacts of these phenomena in driving plague dynamics via their effect on regional climate, and specifically contributing to the foci of transmission on Madagascar, are unknown. Here we present the first analysis of the effects of ENSO and IOD on plague in Madagascar.Methodology/principal findingsWe use a forty-eight year monthly time-series of reported human plague cases from 1960 to 2008. Using wavelet analysis, we show that over the last fifty years there have been complex non-stationary associations between ENSO/IOD and the dynamics of plague in Madagascar. We demonstrate that ENSO and IOD influence temperature in Madagascar and that temperature and plague cycles are associated. The effects on plague appear to be mediated more by temperature, but precipitation also undoubtedly influences plague in Madagascar. Our results confirm a relationship between plague anomalies and an increase in the intensity of ENSO events and precipitation.Conclusions/significanceThis work widens the understanding of how climate factors acting over different temporal scales can combine to drive local disease dynamics. Given the association of increasing ENSO strength and plague anomalies in Madagascar it may in future be possible to forecast plague outbreaks in Madagascar. The study gives insight into the complex and changing relationship between climate factors and plague in Madagascar.

It was not until the Third Plague Pandemic where humans began to understand the relationship between bubonic plague, rats and their fleas. Today, we know that the most common way that plague spreads to humans is through the bites of infected fleas. During the Black Death, there were a variety of explanations for the plague's origin, such as punishment from God, bad air or poisoned wells; as the impact of the plague on humans and livestock were the most noticeable features of epidemics, the connection to rats was not established until much later. When the Third Pandemic spread through China, an increase in the number of dead rats was observed in Canton (Guangzhou), and again in Hong Kong during the outbreak of 1894. Investigations This prompted European scientists in Hong Kong to investigate this further as the plague progressed through 1902, and the experiment was repeated in 1903. The 1902 study showed that plague was at epidemic proportions among rats, and the number of dead rats observed correlated with the number of human plague cases. When the experiment was repeated in 1903, plague in rats was at a much lower level, however the correlation was much more noticeable. The conclusions drawn at the time were that the outbreaks peaked when the population of young rats was at its highest, but then declined as the weather cooled and rats were exterminated in larger numbers.

BackgroundYersinia pestis appears to be maintained in multiple, geographically separate, and phylogenetically distinct subpopulations within the highlands of Madagascar. However, the dynamics of these locally differentiated subpopulations through time are mostly unknown. To address that gap and further inform our understanding of plague epidemiology, we investigated the phylogeography of Y. pestis in Madagascar over an 18 year period.Methodology/Principal findingsWe generated whole genome sequences for 31 strains and discovered new SNPs that we used in conjunction with previously identified SNPs and variable-number tandem repeats (VNTRs) to genotype 773 Malagasy Y. pestis samples from 1995 to 2012. We mapped the locations where samples were obtained on a fine geographic scale to examine phylogeographic patterns through time. We identified 18 geographically separate and phylogenetically distinct subpopulations that display spatial and temporal stability, persisting in the same locations over a period of almost two decades. We found that geographic areas with higher levels of topographical relief are associated with greater levels of phylogenetic diversity and that sampling frequency can vary considerably among subpopulations and from year to year. We also found evidence of various Y. pestis dispersal events, including over long distances, but no evidence that any dispersal events resulted in successful establishment of a transferred genotype in a new location during the examined time period.Conclusions/SignificanceOur analysis suggests that persistent endemic cycles of Y. pestis transmission within local areas are responsible for the long term maintenance of plague in Madagascar, rather than repeated episodes of wide scale epidemic spread. Landscape likely plays a role in maintaining Y. pestis subpopulations in Madagascar, with increased topographical relief associated with increased levels of localized differentiation. Local ecological factors likely affect the dynamics of individual subpopulations and the associated likelihood of observing human plague cases in a given year in a particular location.

Plague remains a threat to public health and is considered as a re-emerging infectious disease today. Rodents play an important role as major hosts in plague persistence and driving plague outbreaks in natural foci; however, few studies have tested the association between host diversity in ecosystems and human plague risk. Here we use Zero-Inflated Generalized Additive Models to examine the association of species richness with human plague presence (where plague outbreaks could occur) and intensity (the average number of annual human cases when they occurred) in China during the Third Pandemic. We also account for transportation network density, annual precipitation levels, and human population size. We found rodent species richness, particularly of rodent plague hosts, is positively associated with the presence of human plague. Further investigation shows that species richness of both wild and commensal rodent plague hosts are positively correlated with the presence, but only the latte...