Major Epidemics and Their Impact on the World

Introduction

It’s hard to imagine -in this day of super antibiotics and advanced medicine - but there was a time in history when a single disease could cause the deaths of thousands of people virtually overnight. Throughout history many outbreaks of diseases occurred to leave behind them millions of dead bodies, some even went so far to taint the health of most of the population. Fear and agony were spreading alongside it, stealing children and loved ones and forcing people to immigrate out of this thought-to-be-cursed land …. I will be discussing the major, and most devastating epidemics across the history, their causes, what lead to the spread of the disease in the first place and what effects did each epidemic had brought with it.

Bubonic plague

Overview

All huge outbreaks of lethal diseases in human history have been called plagues to emphasize how unpleasant and frustrating these outbreaks were. However, whenever actual bubonic plague makes its grand appearance, quarantine measures are issued, panic and stress spreads alongside the epidemic, and people flee the area. With its unfortunately high mortality rate and sadly rapid spread, bubonic plague remains one of the most severe outbreaks of disease the history has ever witnessed. Although plague is primarily a disease of rats and other tiny animals(zoonosis), especially fleas found on top of rodents, its effects on humans are significant and severe. Moreover, it has been spread widely by humans through the accidental transport of rats and their fleas. Finally, it has been intentionally exploited as a form of biowarfare since the first appearance of the Black Death in the Crimea, through World War II, and it may be used again in the future.

Symptoms

Nowadays named bubonic plague because of the painful, swelled, abscessed lymph nodes (buboes), it produces, bubonic plague was also called the Black Death during a catastrophic pandemic in the mid-fourteenth century. The name most likely originated because patients with severe form of the disease developed septicemia, which is a widespread(systemic) contamination of the blood. This, in turn, leads to a syndrome formally known as disseminated intravascular coagulation (DIC), in which multiple hemorrhages and patches of gangrene develop in the skin, turning large areas of the body black.

Transmission and spread

Bubonic Plague does not normally spread directly from person to person; its spread caused by small animal hosts, most of which rats and their fleas. Hungry fleas feed on diseased or rather infected rats, when these rats die, those fleas can hop on to a human host. Bubonic Plague can be spread directly from person to person when it leads to pneumonia(pneumonic plague) and, although the same little creatures that cause the bubonic form of the disease can result in pneumonia, severe lung disease does not occur often enough to rely on airborne pathogens to purposely spread the disease. If these bacteria-containing droplets are breathed in by another person they can cause pneumonic plague. Human-to-human transmission is rare and typically requires direct and close contact with the person with pneumonic plague. The septicemia that is found in tremendously sick patients can spread the disease without the assistance of rats. A flea directly feeding on the septic blood of a plague patient could pick up enough numbers of microorganisms to infect another human with its bite. Although primarily a disease of rats and other small mammals, and their fleas, bubonic plague is spread from location to other by human travel and commerce, a perfect route for the migration of the animal causatives of the disease.

Dr. Shibasaburo Kitasato apparently was the first to observe the bubonic plague up-close but published his findings in Japanese and English. Dr. Alexandre Yersin found the same microorganism and recognized its role, but he published his findings in French through a leading scientific journal of the time that quickly published short reports. hence, his work appeared first. Yersin’s priority of publication made him claim the credit of this amazing finding, and in 1970, the organism was named Yersinia pestis.

Even though the success of rat-catching campaigns, it is worth noting that reducing the rat numbers could have significantly increased the widespread of plague, at least for a short time. eradicating rats minimizes the reservoir of infection, but leaves starving fleas looking for a brand-new source for their delicious bloody meal. Humans are the perfect alternative source of nutritious blood. Thus, humans are more prone to get infected by fleas bites as a result of the elimination of the rat population, at least until the population of infected fleas dies off. In many Middle Ages epidemics, the documents show that the finding of many dead rats in a community was almost immediately followed by an outbreak of human cases of plague. (The New Mexican couple who recently became ill with plague in New York City had found a dead rat on their property just before leaving for New York, but they were not aware that they had been bitten by its fleas.

Vaccinations

Catching the microorganism Yersinia pestis can be prevented in individuals through vaccination. However, vaccination can’t eradicate plague completely. Because of its rodent reservoir, the infection can rise again whenever unvaccinated individuals appear in a given vaccinated area. To prevent any cases of the disease One hundred percent of a population must be vaccinated. The vaccination of American troops in Vietnam stopped the spread of infection in the troops, but it did occur in the native population.

Smallpox

Overview

The medical history of smallpox is a forgotten narrative of untold human agony, unanticipated human creativity, and ultimately extraordinary human success. Smallpox was a hideous disease, spreading around the globe from a long time ago to modern times. It was transmitted by an invisible virus; it struck an individual person and infected entire populations with unpreceded speed; and it turned out to be fatal to nearly one-third of its sufferers. Those who somehow survived a devastating two-week period of skin eruptions, fever, and internal organ damage were usually left with massive scars and occasionally blinded. Unfortunately, there was no cure.

Origin

The word smallpox was created in the 16th century, to differentiate between this illness and syphilis, which then became widely known as “the great pox”, for the slight differences in the skin rashes the two diseases could induce. When, how, or where the smallpox virus first appeared on earth? No one knows for sure. However, we do know that it has traveled the planet more than one time across many centuries, intruding into every place inhabited by humans. We also found out more generally that the existence of different forms of microbiological infection(one of two virus variants, Variola major and Variola minor for the case of smallpox) is probably almost as old as the start of life itself.

Transmission

Three distinct features of smallpox formed its transmission patterns. First, the disease traveled from one person to the other through relatively close contact, the virus can be carried by the air for small distances or spread by direct physical contact with an infected person or with his or her belongings. second, the disease affected humans exclusively; there is no reservoir for variola in flora or fauna (the plants or animals of a particular area respectively), air, or soil, as there is with so many other disease agents. Third, anyone who catched the disease and was able to survive it thereby acquired a long-lasting immunity thus it essentially never infected the same person more than once. Consequently, adolescents whose faces showed its characteristic pitted scars were much in demand as nannies and servants; anyone else could be a victim for variola virus.

Cause and Symptoms

By the 18th century, when smallpox was wiping out an average of 400,000 people per year in Europe solely, leading medical departments in many countries had begun to distinguish smallpox from other akin impairments and had developed a sophisticated comprehension of smallpox’s disease development. In a “standard” case, variola virus was believed to be introduced to the human body through the lungs (saliva droplets in an infected person's breath) or less frequently, the skin. Smallpox typically started with (the “pre-eruptive stage”), a ten to fourteen-day latency or incubation period shortly after the first exposure during which the infected person showed no signs or symptoms of variola. For the following three days (the “prodromal stage”), multiple flulike effects would kick in, for instance, most victims complained from a fever, nausea, headache, backache, chills, delusions, convulsions and a scarlet rash that might appear on their face or body. Then, surprisingly, for a day or two, the fever would vanish, and the victim would feel a lot better, as if cured from some other, less fatal disease. However, At the next phase (the “eruptive stage”), the variola infection worsenes. A rash would emerge and spread rapidly all over the body, more noticeably on the extremities and face than on the trunk. Little by little, the regions of the flat rash would rise to form pimples, blisters, and, finally, pustules. Those would eventually dry into scabs or crusts. The skin would turn pink, then red, as if it had been scalded or set-on-fire; It would feel hot when touched and would occasionally peel off. Patients Eyes were a common target, 1% of smallpox survivors were left blind in one or both eyes due to ulceration of the cornea. Internally, the virus would affect the liver, heart, intestines, lungs and other organs. For people who manage to survive variola, permanent scars on the skin, of significant numbers and varying intensities, were a characteristic stamp left by disease.

Treatment

The horrors and suffering brought by the smallpox inspired a wide variety of innovative treatment regimens, derived in each era from the beliefs and misunderstandings of the origins and nature of the diseases. Many early civilizations for example, offered sacrifices, practiced bloodletting or even, though counter-intuitively “heat therapy”, many patients died from the extreme and ineffective treatments of the time. However, some used inoculation or variolation which amounted to intentionally inducing a mild form of the disease, in the hope that the person would recover and thereby gain a lifelong protection against the disease.

The Fall of Smallpox

The risk of death following contracting the disease was about 30%, with higher rates among babies. Smallpox is estimated to have killed up to 300 million people in the 20th century and around 500 million people in the last 100 years of its existence. The last naturally occurring case was diagnosed in October 1977 and the World Health Organization (WHO) announced the global eradication of the disease in 1980.

Cholera

Overview

Economic loss in underdeveloped countries, most often centered in tropical areas of the world. Generally, V. cholerae is transmitted through contaminated food and water in communities that do not have access to proper sewage and water treatment systems and is thus called “The disease of poverty”. Preface Cholera is a life-threatening diarrheal disease that can spread rapidly and in explosive epidemics from one region to another, affecting large numbers of people. V. cholerae, a gram-negative motile bacterium, is the causative agent of this intestinal disease.

The organism

Vibrio cholerae, a Gram-negative bacterium is known as the causative agent of cholera, acute watery diarrhoea. Out of approximately 206 serogroups of V. cholerae, onlyO1 and O139 are thought to be capable of causing epidemic cholera. These serogroups contain genes for cholera toxin(CT) and toxin-coregulated pilus (TCP). Strains belonging to about 204 other than O1 and O139 serogroups are collectively referred to as non-O1, non-O139 strains. The majority of non-O1, non-O139 strains do not contain genes for CT and/or TCP, although the gene for toxin regulatory protein (ToxR)is generally present in these strains. These strains are ubiquitous in aquatic environments and have been recognized as the causative agents of sporadic cholera-like disease and outbreaks.

Effects

Cholera, which is caused by pathogenic strains of Vibrio cholerae, continues to threaten public health and socio-economic development in many developing countries, particularly those that lack access to potable water and adequate sanitation. The cumulative total number of cholera cases reported to the World Health Organization (WHO) during 2004 to 2008 (838 315) showed an increase of 24% when compared to the period 2000 to 2004. Of the 5 143 cholera fatalities that occurred worldwide in 2008, 98% were from Africa.

Transmission

The emergence of new V. cholerae strains and the severity of recent cholera outbreaks that began in August 2008 in Zimbabwe, coupled with climate change and elevated antimicrobial resistance, highlighted the dynamics of cholera. For these reasons, cholera was placed at the forefront of world public health agenda. Transmission of V. cholerae is through the fecal-oral route after ingestion of contaminated water and food. Previously, it was assumed that cholera was only spread by infected people to susceptible hosts through fecal contamination of water and food. However, it is now known that V. cholerae are normal inhabitants of surface water and can survive and multiply independent of the human host. These strains may then cause cholera depending on environmental factors, hence a thorough understanding of the ecology of V. cholerae is inevitable to minimize contact with this pathogen.

Treatment

The primary treatment of cholera involves electrolyte replacement through oral rehydration. Whilst antibiotics are often indicated for treating severe cholera cases, the standard medical approach for prophylaxis against cholera entails vaccination against pathogenic V. cholerae strains. cholera transmission can be contained effectively by moving from a reactive to a prevention approach. For this purpose, holistic principles that encompass a coordinated multidisciplinary approach, which ensures potable water supply, protection of water distribution systems, improved sanitation and health education must be used.

Coronavirus: Malaria and Yellow Fever

Overview

At the time of the 1878 Memphis epidemic, the germ theory of disease was becoming accepted and the science of bacteriology established. However, the possibility of insect transmission of an infectious agent had not yet been demonstrated, and the concept was ridiculed. Malaria and yellow fever are two devastating diseases spread by the bite of specific species of mosquitoes.

Malaria

Even so treatment and prevention methods have been discovered since 1633, malaria cases are still showing worldwide and are a significant cause of death, mostly in youth. For a long time, malaria was thought to have been the result of harmful emissions from decaying organic substance(miasmas). The observation that the most harmful emissions arose from swampy regions was based on the frequent occurrence of the disease near those areas. Because another name for such airborne toxic emissions was mal--aria or bad air, the term malaria used to refer to all diseases thought to be a result of miasmas.

Origin

The first clue of malaria parasites was found in mosquitoes preserved inside an amber from the Paleogene period that is approximately 30 million years old. The malaria parasite is similar to one that affects Old World apes. The disease is thought to have widely advanced from the rain forest of tropical Africa, migrating slowly into the Nile Valley and the Fertile Crescent, and then to the northern shore of the Mediterranean. Despite that the evidence for the presence of malaria in Greece after 500 BCE is convincing, it is uncertain when it first appeared in that area. Evidence for malaria in Ancient Egypt is much less abundant, but one very interesting possible example is the mummy of a weaver named Nacht, who was a servant of the Pharaoh Setnakht, first ruler of the twentieth dynasty.

Cause and Symptoms

The time the symptoms start to show up is based on the time it takes for the causative organisms to fully mature and breed in the red blood cells. Hence, once mature they cause the red cells to rupture, releasing huge numbers of tiny organisms into the blood, leading to fever and chills, therefore, permitting the organisms to enter other red blood cells and restart the cycle again. Statistically, the most common organism, Plasmodium vivax, takes about 48 hours to complete the cycle, and thus the fever and chills take place every other day (relapsing fever). This loop or cycle was called “tertian” by the Ancient Greeks. Thus, the following chill/fever took place on the third day of the new cycle.

Malaria today

Malaria is still the most relevant parasitic disease affecting humans. Unfortunately, it is known to be present in ninety countries, with more than 300 million cases occurring each year, most of which are children. Factors unrelated to human activities can extend the disease, mostly wet climates, which greatly affects the breeding regions for the mosquito. Global warming may be a factor in proliferating the range of insect vectors and increasing the areas in which the vector can remain.

Yellow fever

Although yellow fever has probably always existed in tropical areas of the ancient World, it did not appear in the Newspapers until the middle of the seventeenth century, it has probably originated across the Atlantic from Africa by the slave trade. Yellow fever lasted as an endemic in tropical areas of the Western Hemisphere and, away from those regions, it often led to problematic and severe summertime epidemics extended primarily by travelers.

Cause and Symptoms

Yellow fever is a widely spread infection, some form of viral hepatitis that causes massive death of the liver tissues and results in severe jaundice (which causes yellowish skin and mucus membranes), hence the name. The patients suffer severe headaches, kidney abnormalities, and gastrointestinal hemorrhage that leads to vomiting of black material. The disease is propagated by a mosquito that can survive a whole year in tropical areas.

The observations of Dr. Carlos Finlay of Cuba had a great influence. Finaly, a native from Havana, was much loved and respected as a person and a physician, and despite his busy practice he dedicated some time to study the devastating yellow fever and its transmission. He was well aware of the suggested vector role of mosquitoes and performed a thorough study of Havana’s mosquitoes. He interpreted that only the female mosquitoes suck blood from mammals. He showed that this happened after fertilization by the males, and that the warmth of the blood induced the female to ovulate. Finaly, assumed that the mosquitoes were drawn to patients with fever, since the warmer the blood, the faster ovulation took place. Thus, mosquitoes would be most attracted to patients with yellow fever, hence significantly increasing the spread of the disease.

Impact on Modern Medicine

The control of yellow fever (and malaria) required proof of the mosquito’s role in the spread of disease, and the studies that established this role lead to some of the most dramatic and important episodes in the history of preventive medicine. The mortality rates for yellow fever were 30 to 50 percent, similar to the outbreaks of other deadly diseases such as smallpox, cholera, and even bubonic plague.