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epidemic

[liú xíng bìng]

Diseases with the occurrence level exceeding the expected standard (causing epidemic phenomenon)

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epidemic An infectious disease that can infect a large number of people. Epidemics can only occur in a certain area, or they can be global Pandemic 。 In European languages, the etymology comes from Greek , such as English epidemic , French é pid é mie, etc. When the observed value of a disease exceeds the expected value, it is called epidemic. The global epidemic is defined as the infection of a disease that has crossed the boundary between continents.^[1]

Chinese name: epidemic
Foreign name: epidemic

Example: AIDS, Black Death, Spanish Influenza
Hazards: Cause human death

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Whether the continuous occurrence of an infectious disease can be regarded as epidemic, that is, the so-called narrow epidemic, the main determinant is not the proportion of the population infected with the disease; It is the speed of transmission of the disease. If each infected person passes on the disease to more than one person, so that the overall infected population increases exponentially, this infectious disease is an epidemic. So even if only a few people are infected with an infectious disease, it can still be called an epidemic outbreak.

When an infectious disease is epidemic:

R0 is the disease Basic infectious number ， S It is the proportion of the population that may be infected. This is for the definition of epidemic mathematical model 。

Epidemic examples in history include: the Black Death in medieval Europe（ plague ）， the First World War Eruptive Spanish influenza , and recent AIDS 。

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swine flu 、 SARS 、 avian influenza 、 COVID-19 。

Influenza

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Influenza Referred to as "flu", it is a very common infectious disease caused by influenza virus.

Influenza is mainly caused by Airborne transmission , via respiratory tract Enter the human body. When people talk and breathe, especially when they cough and sneeze, they can spit out tens of thousands to millions of saliva droplets. If a healthy person inhales droplets containing influenza virus, the person may suffer from influenza.

Influenza patients can discharge a large amount of influenza virus, which is important Infectious agent Generally, severe patients have to be hospitalized or rest at home for treatment, while mild influenza patients can not only release virus, but also move around, so the spread range and harm are greater. Some people infected with influenza virus may have no symptoms and become Recessive infection It is not easy to be found. But these recessive infections can also release virus through saliva droplets, and also spread influenza.

In addition, patients can also have influenza virus on their hands, which can spread. For example, people shake hands with each other, children hold hands with each other, share toys, etc., which may be infected with influenza virus and get sick.

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smallpox

As early as the 16th century, European explorers Colonist And before the conquerors entered the new continent, America There are nearly 100 million people living on the mainland Indigenous peoples 。 However, in the following 100 years, the outbreak of infectious diseases sharply reduced the population to 5 million to 10 million. Although some of them aborigines , such as Inca People and Aztecs have begun to build cities. However, due to the short time, they have not domesticated a large number of animals, nor have they bred many bacteria that invade Europeans. But with the arrival of European colonialists, many infectious diseases that indigenous people could not resist also came to the new continent.

The most serious of these infectious diseases smallpox 。 The smallpox pathogen has been found in humans Social communication For thousands of years, the most serious disease will cause 30% mortality 。 Symptoms of smallpox include high fever, body aches rash , blisters and Permanent Scar. This disease is usually transmitted through direct contact with the patient's skin or body fluid, but it can also be transmitted through the closed environment Airborne transmission 。

Although in 1796 Smallpox vaccine Has appeared, but Smallpox virus It is still spreading. Even in 1976, smallpox caused the death of 20000 people and panic of millions of people around the world. In the same year, world health organization Mass vaccination against smallpox began. In 1977, smallpox cases disappeared completely. Now, this Viruses Apart from the laboratory, it has disappeared in nature.

In the next section, we will learn about the influenza virus 。

Spanish flu

In 1918, when the First World War ended, 37 million people died in the war, and millions of soldiers began to return home. Then a new disease appeared, which some people called Spanish flu , or century old influenza And 1918 flu. The disaster took 20 million lives in a few months. Within a year, the flu continued to spread, death toll It's amazing. It is estimated that 50 million to 100 million people worldwide have died of the disease. The flu is considered to be the most serious in human history plague 。

The Spanish flu is different from the common flu I now encounter every year. It is a new type of influenza virus, called H1N1 Avian influenza virus. Scientists suspect that the virus is World War I Previously from the United States Central and western regions Of birds Infectious to humans. Later, 8 million people died in Spain, so this flu is called“ Spanish flu ”。 Globally, most human beings are completely free of this virus Resistance Just like the plight of Aztecs when facing smallpox in 1550. Large scale transportation and supply forces make the virus spread to other areas more quickly.

The 1918 flu also had typical symptoms of ordinary flu, such as have a fever , nausea abdominal pain And diarrhea. Similarly, patients often have Black spot The lung is filled with liquid, which is easy to lead to hypoxia, and patients with this disease often die of lung fluid filling.

With the mutation of the virus and its shift to a non lethal direction, the flu gradually disappeared a year later. For us, due to the combination of genes and some antibodies genetic , Yes H1N1 All viruses in the family have certain resistance.

If you are interested in dark art, continue to read The Renaissance The Black Death.

Black Death

The car was piled with corpses, and the plank was filled with dead families. The nobles and farmers wailed in unison, hoping to enter heaven and get relief. This is the Black Death, the most terrible infectious disease in human history. The Black Death is considered to be the first real large-scale Epidemic infection Illness. In Europe in 1348, half of the people died of the Black Death. At that time, many people died in China and India. The Black Death continued to spread along the route of war and trade. Cities and villages along the route were completely destroyed, and the global politics and economy were fatally hit.

The Black Death has long been considered an epidemic plague , through the mouse flea And air. But recent studies have questioned this. Some scientists believe that the Black Death may be a hemorrhagic virus similar to Ebola virus. Scientists are studying Plague Suspected victim Of remains We hope to find some genetic evidence to confirm this theory.

If the Black Death is a plague, it still exists. By Yael Sen's The plague caused by Bacillus will now occur in some poor areas where mice are rampant. But only some simple treatment in the early stage of the disease can greatly reduce the disease. The main symptoms of this disease include Lymph gland Swelling, fever, cough ， Blood sputum and dyspnea 。

After reading the next section, you must not hesitate to slap your body mosquito 。

malaria

malaria It is not a new infectious disease. The earliest record of malaria appeared 4000 years ago, when the Greeks described the devastating effects of malaria. First about mosquito son transmit illness The statement of ancient India And Chinese medical books. Even now, scientists have found that many diseases are related to mosquitoes.

Malaria is generally caused by mosquitoes and humans plasmodium Caused by microorganisms. When the infected mosquito stays on the human skin and starts to suck blood, the malaria parasite microorganisms will enter the human body. Once in the blood red blood cell It grows inside and eventually destroys red blood cells. Symptoms range from mild to severe. The typical symptom is fever. Cold, sweating, headache And muscle pain. For more information, see the pathogenesis of malaria.

The transmission of malaria in ancient times is now difficult to verify. But we can still see its amazing Destructive power 。 In 1906, U.S. government 26000 workers were recruited to build panama canal 。 Of these, 21000 were later hospitalized for malaria.

Soldiers in wartime suffer malaria Is the most harmful. It is reported that only the United States Civil War Among them, 1316000 people were infected with malaria, of which about 10000 died. During the First World War, British, French and German soldiers suffered from malaria for three years. the Second World War During this period, the United States Africa and South Pacific Sixty thousand of the soldiers in our garrison died of malaria.

At the end of World War II, the United States tried to eliminate malaria. They first used DDT, which is now banned（ DDT ）We will kill mosquitoes on a large scale, and then prevent mosquito breeding. In the United States Disease Control Center After declaring that malaria has disappeared in the United States, world health organization Start to eradicate on a global scale malaria 。 But with Drug resistance The emergence of malaria and mosquitoes has forced the eradication of malaria, which has cost huge human and financial resources, to run aground.

Today, malaria is still rampant in many parts of the world. Especially in those who have not implemented the World Health Organization action to eliminate malaria sahara desert In the southern region, nearly 350 million to 500 million people are infected with malaria every year, Up to one Millions of people died as a result. Even in the United States, despite the previous major clean-up, there are more than 1000 cases every year and a few deaths.

In the next section, we will learn about a Ancient Egypt Infectious diseases already existed in the era.

pulmonary tuberculosis

Since written records, pulmonary tuberculosis It exists in the world. Ancient novel The death process of pulmonary tuberculosis patients was recorded in detail. People even in ancient Egypt mummy The presence of pulmonary tuberculosis bacteria was found in DNA Evidence.

Tuberculosis is caused by Mycobacterium tuberculosis Caused by and relied on in the crowd Airborne transmission 。 When the infected person breathes, the bacteria come out and then enter other people. Common bacteria Direct attack Lung, causing chest pain, weakness, weight loss, fever, night night sweat And blood sputum. Sometimes it affects the brain, kidneys or spine.

Since the 17th century, tuberculosis has been Continental Europe It has been popular for nearly 200 years, and nearly 1/7 of the infected people died. Tuberculosis in American colonies More common. Even in the late 19th century, the United States Death population One in ten people still die of tuberculosis.

In 1944, the medical profession invented antibiotics to treat pulmonary tuberculosis And made breakthrough progress. After 5000 years of torture, we can finally get rid of this infectious disease, which was called "the disease of death" by ancient Egypt.

Despite the help of modern treatment methods, nearly 8 million people are infected with tuberculosis every year, and 2 million of them die.

Global poverty due to ineffective prevention and treatment, and Drug resistance tuberculosis With the emergence of bacteria, this disease made a comeback in the 1990s. In addition, AIDS patients immune system It is damaged, so it is more likely to be infected with tuberculosis. With the spread of AIDS, tuberculosis has also begun to resurge.

In the next section, you will learn why hydrate Drinks help heal cholera 。

cholera

Ancient India Already have cholera There were cases, but similar cases did not appear in other parts of the world until the 19th century. In the 19th century, the cholera virus entered China, Japan North Africa 、 Middle East And some cities in Africa. Six large-scale Cholera outbreak , taking millions of lives.

Cholera is caused by a disease called Vibrio cholerae Of intestinal bacteria. Mild infection is very common. 5% of infected people may have severe vomiting, diarrhea and Leg cramp , even severe dehydration and shock. Most people's immune system can resist cholera, provided that you can stay dehydrated for a long time. direct contact Patients are usually infected with the virus, but cholera virus is mainly transmitted through contaminated water and food.

In the 19th century, Europe industrial revolution During this period, the cholera virus was brought to Europe by traders Commercial city 。 Doctors cholera The reason for the epidemic is due to serious air pollution. They advocate clean environment And increase Sewage treatment system 。 This has a good preventive effect on the prevalence of cholera. Although the medical community finally decided that cholera was not caused by Airborne transmission However, cholera cases have been greatly reduced due to the urban cleaning plan.

In the last century, people always believed that cholera was just an old thing in the 18th century. With the progress of science and the improvement of health conditions, cholera virus was eradicated early. Then, in 1961, a new type of cholera Indonesia And finally spread to the whole world. The epidemic cholera has continued to this day. In 1991, 300000 people were infected with the new cholera, and 4000 people were killed.

AIDS has always been a disease of great concern, and films, television and novels on AIDS have won many awards. In the next section, we will learn about this incurable disease.

AIDS

The emergence of AIDS in the 1980s triggered a worldwide disaster. Since 1981, about 25 million people have lost their lives. Latest statistics data display There are 33.2 million people in the world HIV carrier In 2007 alone, 2.1 million AIDS patients died [Source: Avert].

AIDS（ Acquirability Immunodeficiency syndrome ）It is caused by human immunodeficiency virus (HIV). The virus spreads through human blood, semen and other body fluids and directly damages Human immune system 。 People whose immune system is destroyed have no resistance to all kinds of germs, also known as Opportunistic infection （Ols）。 If the human immune system is Severe damage HIV becomes AIDS.

Scientists suspect that HIV was caused by monkeys and Anthropoid ape Infectious to humans. In the 1970s, the population of Africa grew rapidly, and war, poverty and unemployment plagued African countries. Prostitution and drug abuse are rampant, HIV It is also spread through unsafe sex and contaminated needles. Even in hospitals, the repeated use of needles and unsafe blood transfusion also facilitate the spread of AIDS. Soon, AIDS was rampant in the sub Saharan region, and the labor force in many poor countries died as a result, and thousands of children became orphans.

Although some drugs can inhibit AIDS Carriers develop into AIDS patients, but at present there is no drug that can completely cure the disease. Many groups and organizations are carrying out AIDS prevention publicity and education activities. As mentioned above, HIV It is generally transmitted through unsafe sexual intercourse and repeated use of infusion needles. Therefore, the medical department has been calling for the use of Condom And disposable needles to prevent the spread of AIDS. For more information about AIDS, please see what AIDS is.

In the next section, we will learn about a more serious infectious disease—— yellow fever It once defeated Napoleon's army.

yellow fever

When European colonialists transported a large number of African slaves to the Americas, many new infectious diseases were also brought there, including yellow fever 。 Yellow fever, also known as "Yellow Jack", spread widely in colonial areas, resulting in the disappearance of a large number of farms and the devastating impact on some major cities.

In 1803, Napoleon sent 33000 people to North America After the army landed in France, 29000 people died of yellow fever. Huge losses forced Napoleon to abandon the territory. Subsequently, France sold the territory to the United States. This is recorded in history books Louisiana Events 。

Yellow fever and malaria Similarly, it is transmitted through mosquitoes. Typical symptoms include fever fever , headache, muscle pain, backache and vomiting. Severe infection can lead to bleeding, shock, kidney and Liver failure , there is a fatal danger. Liver failure can lead to jaundice Sick or Yellowing of skin This is what it is called“ yellow fever ”Reason for.

Although vaccination , improve living environment and eliminate mosquitoes on a large scale. Yellow fever is still in Africa and South America Rage.

In the next section, we will learn that soldiers should not only avoid bullets, but also prevent Epidemic typhus 。

Typhus

Many people are crowded together in a dirty environment, and everyone keeps grabbing Lice 。 Since ancient times, soldiers sleeping in the battlefield must not only guard against the enemy, but also face parasite And the threat of germs. A tiny pathogen called Rickettsia prezewalskii once led to the world famous plague outbreak, that is Typhoid disease 。

Because it often breaks out in the garrison, it is also called "camping fever" or "war" Typhoid fever ”。 In Europe Thirty year war period, Typhus , plague and hunger took 10 million lives. Sometimes, the outbreak of typhus will determine the outcome of a war [source: Conlon].

In 1489 Spanish Army When the Moors' stronghold Granada was besieged, a typhus outbreak broke out, and the Spanish army was suddenly reduced from 25000 to 8000 [source: Conlon]. Due to the destruction of typhus, the Spanish could only wait for the next century to expel the Moors from Spain. There were similar events in World War I, typhoid fever caused millions of Russia 、 poland and Romania The soldier died.

Typhus Typical symptoms of Anorexia , fatigue and body temperature rise sharply, and quickly turn to fever, accompanied by chills and nausea. If not treated in time, typhoid will affect blood circulation , causing spots gangrene 、 pneumonia and Renal failure , as the temperature gradually increases, eventually leading to Insanity , coma and heart failure 。

Now, with the progress of medical means and the improvement of sanitary conditions, typhus has gradually decreased. In World War II Typhus vaccine The use of DDT and the implementation of DDT mosquito control action have made typhus developed country It has disappeared. But in South America, Africa and Asia In some areas, typhus has not been eliminated.

In the next section, we will see that with sanitary conditions and living standard The number of people paralyzed by illness has increased.

poliomyelitis

poliomyelitis Also called polio. Researchers speculate that the disease has been rampant around the world for thousands of years, resulting in paralysis or death of thousands of children. In 1952, there were about 58000 polio cases in the United States alone, and one third of them were paralyzed. In these cases, more than 3000 people died.

This disease is caused by destruction Human nervous system Of Poliovirus （ poliomyelitis ）Cause. It can spread through feces and through contaminated food and water. Initial symptoms include fever, fatigue, headache, vomiting, stiffness and Limb pain 。 About one person in every 200 infected persons will be paralyzed [Source: WHO ]。 Although paralysis symptoms are mainly concentrated in the legs, it sometimes spreads to respiratory system Of Muscle tissue , resulting in death of the patient.

poliomyelitis Most patients are children, so they are also called poliomyelitis, but adults can also be infected with this disease. This mainly depends on how old the patient was when he first came into contact with the virus, that is, when he first became infected. In adolescence, Human immune system It is more resistant to poliomyelitis. Therefore, the older the patient is at the time of initial infection, the greater the risk of paralysis or death.

Poliomyelitis is a very ancient disease, which has spread for thousands of years in the human world. If you have been exposed to poliomyelitis bacteria in your childhood, your body's own resistance will be improved accordingly. But by the 18th century, our medical means had made great progress. This limits the spread of disease and reduces people's exposure to germs in childhood. As a result, more and more patients will not be exposed to poliomyelitis bacteria until they are older. Therefore, in developed countries, the proportion of paralysis caused by poliomyelitis has risen sharply.

At present, there is no target for poliomyelitis But in the 1950s, the medical community developed Polio vaccine 。 Since then, the disease has been basically controlled in developed countries, only in some cases developing country Only then will there be an epidemic outbreak of poliomyelitis. Humans are the carriers of this pathogen, and broad-spectrum vaccines can almost guarantee the eradication of polio. In 1988, world health organization The global polio eradication plan launched is to achieve this goal.

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