"Smallpox is an infection caused by the variola virus, a member of the poxvirus family. Throughout world history, smallpox has caused epidemics resulting in suffering and death. In 1980, the World Health Organization (WHO) announced that a massive program of vaccination against the disease had resulted in the complete eradication of the virus (with the exception of the known stored virus in two laboratories)."
STEM : Stop the Spread
Investigate a communicable disease
Pandemics
A pandemic is an outbreak of an infectious disease that spreads among many people over a wide geographical area. It generally affects a significant proportion of the world’s population, usually over the course of several months. The outbreak can affect many millions of people worldwide. Pandemics arise from epidemics, which are outbreaks of disease confined to one part of the world, such as a single country. Pandemics, especially those involving influenza (flu), sometimes occur in waves. After an initial wave with many people becoming infected, there may be a phase of decreased disease activity. After that, there may be another wave when many more people catch the disease.
Pandemic. (2021). In Encyclopædia Britannica. Retrieved from https://school.eb.com.au/levels/middle/article/pandemic/632229
Pandemics and Epidemics
The Black Death made its first appearance in western Europe in the Sicilian port of Messina in October 1347. The plague moved rapidly, at a rate of about 2 miles per day, and decimated populations in its wake.
Gale
Click the link above to be taken to Encyclopedia Britannica and choose Middle School.
Search term - plague
Between 1347 and 1351 a great epidemic known as the Black Death ravaged Europe. This pandemic took a proportionately greater toll of life than any other known epidemic or war up to that time. The Black Death is widely believed to have been the result of plague that was caused by infection with the bacterium Yersinia pestis. Most scientists think that this bacterium was first passed from infected rodents to humans through the bite of fleas. Then it spread quickly from one person to another.
Black Death. (2021). In Encyclopædia Britannica. Retrieved from https://school.eb.com.au/levels/middle/article/Black-Death/574643
"The Black Death, also called the Great Plague, refers to a bubonic plague that swept across Europe in the mid-fourteenth century. Black Death was so named because of the black boils that covered the bodies of those afflicted, who usually died within days of exposure. The highly contagious disease was believed to have been spread to European trading ports by ships carrying infected fleas. By the time the plague ended, estimates placed the number of fatalities between twenty to fifty million people—about a third to half of the population of Europe at the time."
Black Death. (2019). In Gale In Context Online Collection. Gale. https://link.gale.com/apps/doc/BOAGKV184362120/SUIC?u=61_alls&sid=SUIC&xid=896d241e
Microscopic Illustration Of Coronavirus Disease 2019 (COVID-19) [Drawing]. (2020). UPI Photo Collection. https://link.gale.com/apps/doc/WBDOAZ430891470/SUIC?u=61_alls&sid=SUIC&xid=9372cc23
Click the link above to be taken to Encyclopedia Britannica and choose Middle School.
Search term - coronavirus
Coronaviruses are a group of related viruses that cause illnesses in humans and other animals. Some coronaviruses cause stomach and intestinal disease in humans, poultry and cattle. Others cause respiratory illnesses in humans. Many of the illnesses are mild and are similar to the common cold. A few coronaviruses cause diseases that are severe and very easy to spread from person to person. They can lead to death in humans.
The name coronavirus comes from the way the viruses appear. They have spikes of protein that form a corona, or crown, on their surface.
A few types of coronavirus have caused epidemics of very contagious respiratory disease in humans. (An epidemic is an outbreak of a disease that quickly infects a large number of people.) One type of coronavirus causes a disease called SARS, which is short for severe acute respiratory syndrome. People who have SARS experience fever, cough, muscle ache and often difficulty in breathing. The virus first appeared in humans in 2002 and caused an epidemic in 2003. More than 8,000 cases of SARS were reported. Most of the cases were in China. About 800 people died from the disease.
In 2012 another coronavirus was discovered in humans. The first case was found in Saudi Arabia, and cases were soon identified in other countries of the Middle East. As a result, the illness was called Middle East respiratory syndrome (MERS). MERS cases were later found in Europe, Tunisia, China, Malaysia, South Korea and the United States. All confirmed cases were directly or indirectly linked to the Middle East.
In late 2019 a novel, or new, coronavirus emerged in Wuhan, China. The new virus caused an illness known as COVID-19, which is similar to SARS. People with the illness experienced a fever, a dry cough and, in severe cases, difficulty breathing. The virus was likewise highly contagious. By early 2020 it had spread throughout regions of China. It soon reached all the continents except Antarctica. It was carried by travelers from affected regions. By mid-March cases of COVID-19 were reported in more than 100 countries, with larger outbreaks in China, South Korea, Iran, and Italy. Many thousands of people around the world contracted the illness.
Coronavirus. (2021). In Encyclopædia Britannica. Retrieved from https://school.eb.com.au/levels/middle/article/coronavirus/632213
"Coronavirus disease 2019 (COVID-19) is a viral respiratory infection that leads to a mild to severe respiratory illness in those who are exposed to it. Part of the coronavirus family of viruses, COVID-19 first appeared in Wuhan, China, in late 2019 and quickly spread to other countries throughout the world."
READ MORE
Coronavirus: COVID-19. (2020). In Gale In Context Online Collection. Gale. https://link.gale.com/apps/doc/VHLNPX325837945/SUIC?u=61_alls&sid=SUIC&xid=85f094d9
Colourised Ebola virus
Ebola Virus [Medical diagnostic image]. (2015). A. H. Blackwell & E. Manar (Eds.), UXL Encyclopedia of Science (3rd ed.). UXL. https://link.gale.com/apps/doc/PC4205139584/SUIC?u=61_alls&sid=SUIC&xid=e58acff0
Click the link above to be taken to Encyclopedia Britannica and choose Middle School.
Search term - ebola (infectious disease)
Ebola is a highly contagious, or catching, disease. It is caused by a virus called an ebolavirus. The ebolavirus has caused thousands of deaths in Africa since 1976.
ebolavirus . [image]. In Encyclopædia Britannica. Retrieved from https://school.eb.com.au/levels/middle/assembly/view/189954
Cause
There are five species, or kinds, of ebolavirus. Three of the species cause death in humans. Zaire ebolavirus is the most fatal. It causes death in 80 to 90 per cent of cases. One species, the Reston ebolavirus, has been found in the Philippines and in China. It has not caused illness or death in humans so far.
Two species of fruit bats are suspected to be the hosts of the ebolavirus. It is thought the virus is transferred to rainforest animals when they eat food that has come into contact with bat faeces or saliva.
Ebola is transmitted to humans through the blood, organs or bodily fluids of infected animals. Outbreaks in Africa begin when humans handle sick or dead animals. These animals include porcupines, forest antelopes, fruit bats, monkeys, gorillas and chimpanzees. Ebola is spread among humans when an uninfected person comes into contact with infected blood or other infected bodily fluids.
Symptoms
Symptoms of Ebola begin 2 to 21 days after infection. The first symptoms are fever, severe headache, muscle aches and loss of appetite. A few days later, the ebolavirus affects the blood. It creates blood clots in many internal organs, including the liver, spleen and brain. These clots cause bleeding in the surrounding tissue. The patient experiences nausea and expels blood and mucus. A rash begins on the torso and spreads to the limbs and head. Blood then seeps out of any holes or breaks in the skin. Death occurs within 8 to 17 days.
Treatment
There is no known treatment for Ebola. Patients are given fluids to prevent dehydration. Blood and plasma are given to help control the bleeding. Drugs are also being developed and tested. There were treatments used during outbreaks in the 2010s that were successful in saving lives.
It is important to follow the proper steps to stop the spread of the virus. People must wear protective gear when caring for Ebola patients. Close physical contact should be avoided.
Outbreaks
Ebola outbreaks have occurred mostly in villages in central and west Africa. The first outbreaks happened in two different countries in 1976. One outbreak was near the Ebola River in what is now the Democratic Republic of the Congo, which is how the disease got its name. A large Ebola outbreak ravaged western Africa in 2014–15. By the end of the outbreak more than 28,600 people had been infected, and about 11,300 had died in Guinea, Liberia, Nigeria, Mali, Senegal and Sierra Leone.
The second largest Ebola outbreak on record began in August 2018. This one began in the eastern region of the Democratic Republic of the Congo. About 2,800 were infected, and more than 1,800 died. During this outbreak several new medical treatments were tested. Two of the treatments saved 90 per cent of newly infected patients. It is hoped that these treatments will be able to contain future outbreaks.
Ebola. (2021). In Encyclopædia Britannica. Retrieved from https://school.eb.com.au/levels/middle/article/Ebola/610104
"Ebola, also known as Ebola hemorrhagic fever, is a deadly communicable disease found primarily in Africa. The survival rate for a patient with the Ebola virus is roughly 50 percent, depending on the medical care that is available."
A chart shows the number of estimated measles deaths globally from 2000 to 2012. Death rates fell 74 percent, missing an internationally agreed target for 90 percent mainly because of low vaccine coverage in India and Africa; graphic includes map showing countries that have not attained the 90 percent vaccine coverage.© MCT 2012
Measles Deaths 2000 to 2012 [Diagram]. (2012). Tribune Content Agency Graphics. https://link.gale.com/apps/doc/CT3294261211/SUIC?u=61_alls&sid=SUIC&xid=c5e85845
Measles is a highly contagious, serious disease caused by a virus. Before the introduction of measles vaccine in 1963 and widespread vaccination, major epidemics occurred approximately every 2–3 years and measles caused an estimated 2.6 million deaths each year.
World Health Organization. (2019, December 5). Measles. https://www.who.int/news-room/fact-sheets/detail/measles
Click the link above to be taken to Encyclopedia Britannica and choose Middle School.
Search term - measles
One of the most highly contagious diseases in humans is the measles. It is caused by a virus that invades the tissues of the respiratory system, particularly the lungs and throat passages. The most visible sign of measles is a rash that covers the face and body during the course of the disease. Although adults can get measles, it is more common in children. Measles is also known by the name rubeola.
measles . [image]. In Encyclopædia Britannica. Retrieved from https://school.eb.com.au/levels/middle/assembly/view/222571
How Measles Is Spread
When a person infected with the measles virus coughs or sneezes, thousands of tiny particles of the virus are spread into the air. If an uninfected and unvaccinated person inhales these, he or she will become immediately infected. The virus particles make themselves at home in the moist passages of the nose, throat and lungs.
Symptoms
The first symptoms, or signs, of measles appear about 10 to 14 days after a person is exposed to the measles virus. The earliest signs of the disease resemble those of the flu. The patient has a runny nose, a sore throat and a fever. The fever is usually very high, sometimes as high as 40 ° C (104 ° F). The lining of the eyes becomes inflamed and very red. This condition is called conjunctivitis. Tiny bluish white spots appear on the insides of the cheeks. Within several days, a red rash appears on the face and behind the ears. The rash then spreads to the rest of the body.
For most patients, the symptoms of the disease do not go any further. In some patients, however, complications can occur. These include pneumonia, an illness that occurs when the lungs become infected. The measles virus can also attack the brain, causing an illness called encephalitis. This complication can cause the patient to have convulsions or to go into a coma. If the virus infects the liver, it can cause the disease hepatitis. All of these complications are very serious. In some instances, they can be fatal.
Treatment
A case of the measles generally lasts 10 to 12 days, though with complications it will last much longer. The patient must get plenty of rest and drink fluids. Some people who are infected with the measles find bright light to be painful. In these cases, the patient’s room should be kept dark. Because of the danger of complications and also because measles is so easily spread, it is extremely important for the patient to stay home until completely recovered.
Prevention
When a disease is as contagious as measles, it is very important to prevent it from spreading and becoming an epidemic. An epidemic occurs when large numbers of people are infected with the same disease within a short period of time. Epidemics can spread across cities, states and continents. They can even spread around the world.
One way to prevent the spread of disease is through vaccination, or the use of substances that prevent people from getting the disease. Scientists have developed a very effective vaccine against measles. The vaccine also protects against mumps and rubella (sometimes called German measles). It is usually given to children twice before they can attend school. In the United States, the vaccine is widely available. In some countries, it is not available and those countries suffer frequent epidemics. It is very important to discuss the vaccine and the disease with a doctor.
Measles. (2021). In Encyclopædia Britannica. Retrieved from https://school.eb.com.au/levels/middle/article/measles/441024
"Measles is an infectious disease characterized by symptoms such as runny nose, cough, fever, and a red skin rash. Measles most commonly affects children, but adults may also contract the illness. Measles cannot be cured, but it can be prevented for life with a measles vaccine. In the twenty-first century, measles has been nearly eliminated from developed countries such as the United States. In the world’s poorer nations, however, measles kills about one hundred thousand people annually, although more people are becoming vaccinated against the disease every year."
Measles. (2016). In Gale In Context Online Collection. Gale. https://link.gale.com/apps/doc/XTNDMG101703003/SUIC?u=61_alls&sid=SUIC&xid=f6c4e5dc
A world map shows the spread of the deadly smallpox virus during human history.
Smallpoxs Journey Around the World [Photograph, Diagram, World map]. (2011). Tribune Content Agency Graphics. https://link.gale.com/apps/doc/CT3294261200/SUIC?u=61_alls&sid=SUIC&xid=437b1596
Click the link above to be taken to Encyclopedia Britannica and choose Middle School.
Search term - smallpox (disease)
Smallpox is a dangerous disease caused by a germ called a virus. For thousands of years smallpox affected many people. The chances of catching smallpox today, however, are very small.
People who have the smallpox virus can spread it to other people through their breath or saliva. The virus also can live on bedding or clothing. Once a person is infected by the smallpox virus, there is no cure for the disease.
People with smallpox get a high fever. Their body aches and they are tired. A rash appears on their body. The rash changes into blisters, which dry up and become scars. People can die from the disease. People who survive smallpox may have permanent damage, such as blindness.
In 1796 an English doctor named Edward Jenner discovered a smallpox vaccine. A vaccine is a substance that prevents people from getting a disease. In 1967 a group called the World Health Organization began giving the smallpox vaccine to people around the world. The project was a success. By 1979 there were no cases of smallpox anywhere in the world.
Smallpox. (2021). In Encyclopædia Britannica. Retrieved from https://school.eb.com.au/levels/middle/article/smallpox/441713
The disease called tuberculosis, or TB, affects the lungs and sometimes other parts of the body. In the 1700s and 1800s tuberculosis was the leading cause of death in Europe and North America. At that time the disease was commonly called consumption. People who had it were kept – sometimes for years – in special hospitals called sanitariums. Today, tuberculosis is treatable. However, it remains a major cause of death in some countries of Africa, Asia and Latin America.
Click the link above to be taken to Encyclopedia Britannica and choose Middle School.
Search term - Tuberculosis
Causes
Tuberculosis is caused by several types of rod-shaped bacteria. The kind of bacteria that causes most cases in humans is called Mycobacterium tuberculosis. This bacterium infects the respiratory system, especially the lungs. This form of the disease is called pulmonary tuberculosis. A less common form of tuberculosis is caused by a bacterium called Mycobacterium bovis. It affects the bones and joints. Humans get this kind of tuberculosis by drinking milk from an infected cow.
Symptoms
Most of the people infected with the bacteria that cause tuberculosis do not suffer from the disease. The body’s immune system defends against the bacteria by surrounding them with protective cells. The bacteria and the surrounding cells create lumps called tubercles in the lungs. The infection usually heals without causing any symptoms.
Sometimes the infection does not heal and instead spreads into the bloodstream and through the body. This happens mostly in children. In other people the bacteria remain harmless for years before becoming active again in adulthood. This can happen when a person’s immune system is weakened because of advanced age or another illness. These people become ill with pulmonary tuberculosis. Their symptoms include coughing, chest pain, difficulty breathing, fever, sweating, loss of energy and weight loss. The person may cough up blood. If the tubercles spread throughout the lungs, the person may die from not being able to breathe properly.
The form of tuberculosis that spreads from cows to humans first attacks the lymph nodes. The nodes swell in the neck and then burst through the skin to create sores. The bacteria may spread to any part of the body, but usually they damage bones and joints. Eventually the disease causes deformities of the spine or other body parts.
Diagnosis and Treatment
Doctors take a number of steps to find out whether a person has tuberculosis. They perform a special skin test to see if the person is infected with the bacteria that causes the disease. However, the test does not indicate whether the person has the active disease or not. If the skin test shows infection, the doctor can ask for a chest X-ray to see if there are tubercles in the lungs. The doctor may also use a microscope to look for bacteria in the person’s sputum (the matter that the person coughs up).
If the person has tuberculosis, the doctor prescribes a medicine called an antibiotic. Some patients may be hospitalised so that the antibiotics can be given through the veins. If the medications are taken as directed, the person has a good chance of recovery.
Prevention
Tuberculosis spreads most easily in crowded places where living conditions are poor. Therefore, one important way to prevent the disease is maintaining good sanitation and keeping people generally healthy and well nourished. In some countries people are given a vaccine to protect them from tuberculosis.
The type of tuberculosis that is spread through cow’s milk can be prevented by pasteurizing the milk. Pasteurization is a heat-treatment process that kills the disease-causing bacteria. This form of tuberculosis is rare in parts of the world where milk is pasteurized.
Tuberculosis. (2021). In Encyclopædia Britannica. Retrieved from https://school.eb.com.au/levels/middle/article/tuberculosis/441930
"Tuberculosis, or TB, is a contagious disease of the lungs that can spread to other parts of the body and may be fatal. TB is caused by a microorganism known as the tubercle bacillus, or Mycobacterium tuberculosis. The disease can now be treated, cured, and prevented. However, scientists have never come closing to wiping it out and TB remains one of the most serious diseases worldwide. Despite programs to fight TB and improve health care, the World Health Organization (WHO) estimates that 30 million people died of tuberculosis since 2000."
Tuberculosis. (2009). In Sick! UXL. https://link.gale.com/apps/doc/CV2643900134/SUIC?u=61_alls&sid=SUIC&xid=7ecd87bf