Diseases: A brief guide to causes, symptoms, history, and treatment
Since the beginning of human existence on the planet, diseases have played a significant role in the events of every era. This brief listing of some of the most notorious diseases explains their causes, symptoms, history, prevention, and treatment, and provides links to further information.
It would be difficult to overstate the impact of disease on history. Since the beginning of human existence on the planet, diseases have played a significant role in the events of every era. Malaria, one of the oldest known diseases, caused drastic declines in the population of Greek city-states in the fourth century. The Spanish flu epidemic of 1918–1919 killed 20 million people around the world — more than twice the number of people who were killed during World War I. In 1944, a major outbreak of polio around Hickory, North Carolina, overwhelmed the area’s medical facilities, separating sick children from their families and preventing healthy young people from visiting each other for fear of contracting the disease.
Scientific achievements through the ages have greatly alleviated the effects of some of the worst diseases. The formulation of vaccines, the advent of effective mosquito control, and the introduction of modern sanitation to urban areas have rendered diseases like polio, yellow fever, and cholera all but unheard of in the United States. As a result, average life expectancy in the U.S. has risen from 47 years in 1900 to 77 years in 2008. Unfortunately, though, outbreaks of many of the most serious diseases still cause illness and death around the world.
This brief listing of some of the most notorious diseases explains their causes, symptoms, history, prevention, and treatment, and provides links to further information.
Cholera is caused by a bacterial infection of the intestine. In many cases the infection is mild — sometimes producing no symptoms at all. But approximately one in 20 people infected with cholera has a serious case, with symptoms including severe diarrhea, vomiting, and leg cramps. These symptoms quickly cause dehydration and shock, and can result in death within hours if the infected person doesn’t receive treatment.
Cholera is typically transmitted by contaminated food or water. In areas with poor treatment of sewage and drinking water, the feces of people with cholera can enter the water supply and spread quickly, resulting in an epidemic. The cholera bacterium may also live in the environment in some coastal waters, so shellfish eaten raw can be a source of cholera in affected areas.
In the U.S., as in most other industrialized nations, cholera was common in the 1800s but has been virtually wiped out by modern sewage and water treatment systems. Travelers to areas where cholera is endemic may be exposed to the bacterium and can bring it back when they return. The risk of this is very low, however, and can be avoided by taking simple precautions when eating and drinking in areas with epidemic cholera. Also, because the disease isn’t likely to spread through casual contact, returning travelers typically don’t cause widespread cholera outbreaks.
Although some cholera infections can be very severe, and even fatal, the disease can be easily and successfully treated by quickly replacing the fluid and salts lost through diarrhea. With adequate treatment, fewer than 1 percent of cholera patients die from the disease.
To learn more, read “Cholera,” from the Centers for Disease Control and Prevention.
Diphtheria is a serious bacterial disease that affects the respiratory system or the skin. Respiratory diphtheria causes a sore throat and fever, and sometimes swelling of the neck. In severe cases it can cause a membrane to form over the throat, which results in breathing problems. Cutaneous diphtheria affects the skin, causing infected lesions to form. Diphtheria can lead to coma and death if it goes untreated.
An infected person usually spreads the disease by coughing or sneezing. The person expels droplets containing the diphtheria bacteria, which are then inhaled by another person. The disease is treated by hospitalization and antibiotics.
Diphtheria was once very common in the U.S., with hundreds of thousands of cases occurring every year. Since the introduction of a vaccine in the 1920s, cases of diphtheria in the U.S. have declined greatly, with less than one case reported each year since 2000. But while mandatory vaccines for schoolchildren have gone a long way toward controlling diphtheria in the U.S., the disease is still endemic in many developing countries.
To learn more about diphtheria, see “Diphtheria” and “Vaccines and Preventable Diseases: Diphtheria In-Short,” from the Centers for Disease Control and Prevention.
Malaria is caused by a parasite transmitted by infected mosquitoes. Symptoms occur ten days to four weeks after being bitten and are similar to symptoms brought on by the flu — chills, fever, sweating, headache, and muscle pain. In serious cases, malaria may cause vomiting, anemia (iron deficiency), kidney failure, coma, and death.
The disease can be prevented by taking anti-malarial drugs and by avoiding mosquito bites in areas where malaria infection is common. Those infected with malaria can be treated with prescription drugs, which are most effective when taken early in the course of the disease.
The parasite that most often causes malaria needs warm temperatures to grow and thrive, so the disease is typically found in tropical and subtropical countries. Malaria was once common in most of Europe and North America, but effective mosquito control and other measures have nearly eradicated the disease in these regions. While only about 1300 cases of malaria are reported in the U.S. each year, 300 to 500 million cases occur around the world — mostly in developing countries — resulting in more than 1 million deaths from malaria globally each year.
Measles is a highly contagious disease caused by a virus. Early symptoms include fever, cough, red eyes, and a runny nose. During the first few days, the characteristic measles rash appears, beginning with white spots in the mouth and spreading to a red rash that covers the entire body. The rash typically lasts four to seven days. Severe cases of measles can cause diarrhea, ear infection, pneumonia, encephalitis (swelling of the brain), and death.
The measles virus is easily spread through airborne droplets expelled by coughing or sneezing, and can live in the air for up to two hours after an infected person has been present. After exposure, the virus lives in the body for about two weeks before symptoms appear. There is no specific remedy available for measles, so treatment usually consists of bed rest and easing symptoms.
Measles are still quite common, with more than 20 million people infected around the world each year. In the U.S., a widespread immunization campaign has successfully controlled the disease, and fewer than 150 cases have been reported since 1997. About half of these cases result from visits to other countries where measles is still endemic — including some developed countries in Europe and Asia.
Mumps is a contagious viral disease that causes painful swelling of the salivary glands. As a result, people infected with mumps sometimes appear to have “chipmunk cheeks.” Other symptoms include fever, headache, sore muscles, and fatigue. Serious complications are rare, and may include encephalitis (swelling of the brain), inflammation of the sex organs, and deafness.
The mumps virus is transmitted by contact with the respiratory secretions of an infected person. Like measles, mumps has a relatively long incubation period, with symptoms appearing more than two weeks after exposure. There are no specific treatments available for mumps, but the disease can be prevented by immunization. Following the introduction of the mumps vaccine in 1967, reported mumps cases had declined to fewer than 1,000 per year in the U.S. In recent years, however, mumps cases have increased.
To learn more about mumps, see “Mumps,” from Medline Plus, “Mumps,” from Medline Plus Medical Encyclopedia, and “Vaccines and Preventable Diseases: Mumps Vaccination,” from the Centers for Disease Control and Prevention.
Influenza, more commonly known as “the flu,” is caused by a contagious virus. Symptoms include body aches, sore throat, headache, fever, coughing, and chills. Perhaps because influenza is so common, misconceptions about the disease abound. Often, people who experience a bad cold say they have the flu, but this is incorrect: Unlike influenza, colds rarely cause headaches or fever. And despite widespread use of the term “stomach flu,” true influenza does not cause gastrointestinal symptoms.
The flu is spread through airborne respiratory secretions. Symptoms can be serious, and the disease can be fatal — especially for babies, the elderly, and people with weakened immune systems. When influenza pandemics occur, they spread quickly, often killing large numbers of previously healthy people. From 1918 to 1919, a flu pandemic hit the U.S. in three waves. By the pandemic’s end, it had spread over the entire globe and killed about 20 million people. Influenza pandemics occurred again in 1957–1958, and in 1968–1969, although they were nowhere near as severe as the pandemic of 1918–1919.
Influenza is still very common in the U.S.: According to the Centers for Disease Control and Prevention, between 5 percent and 20 percent of Americans get the flu every year, and about 36,000 cases are fatal. The disease can be treated by antiviral medicines, and a seasonal vaccine is available to protect against it. Because the virus changes every year, the vaccine must be reformulated yearly. Doctors recommend that high-risk members of the population get a vaccine at the beginning of each flu season.
For more information about the flu pandemic of 1918-1919, see The Great Pandemic: The United States in 1918-1919, from the U.S. Department of Health and Human Services. To learn more about influenza, see “Flu,” from Medline Plus.
Poliomyelitis (often shortened to “polio”) is a viral infection spread by person-to-person contact. Symptoms vary according to the type of infection, and three basic patterns are common:
- Subclinical infections, which account for the vast majority of polio cases. Symptoms may include fatigue, headache, sore throat, mild fever, and vomiting. In some subclinical infections, no symptoms may appear.
- Nonparalytic poliomyelitis. Symptoms may include back pain, neck pain, fatigue, diarrhea, headache, leg pain, fever, muscle stiffness, painful rash, and vomiting.
- Paralytic poliomyelitis (the most serious kind of polio infection.) Symptoms may include fever, breathing difficulty, constipation, headache, muscle pain, muscle spasms, and muscle weakness on one side of the body. Muscle weakness comes on quickly and progresses to paralysis.
Treatments vary according to the form of the disease, and may include antibiotics, pain-relieving medication, and physical therapy to strengthen weak muscles. In 90 percent of cases a complete recovery is possible. Paralytic cases account for the other 10 percent, which are rarely fatal but typically result in permanent disability.
Polio mainly strikes children under the age of 5, and until the 1950s, thousands of children around the world were permanently disabled by polio. In the late 1950s and early 1960s, scientists developed effective vaccines that nearly eradicated polio as a public health problem in industrialized countries. Efforts are underway to eliminate the disease world-wide, but around a dozen countries have reported cases in the last two years.
For more information about the history of polio and the creation of effective vaccines, see Whatever Happened to Polio? from the Smithsonian National Museum of American History. To learn more about polio, see “Poliomyelitis,” from Medline Plus Medical Encyclopedia, and “In the News: Update on the Global Status of Polio,” from the Centers for Disease Control and Prevention.
Scarlet fever is a disease caused by Streptococcus bacteria — the same bacteria that cause strep throat. The bacteria are spread through contact with the oral or nasal fluids of an infected person. Scarlet fever begins with a fever and sore throat, and later causes a red rash that starts at the chest and spreads over the body. Most cases of scarlet fever occur in children under the age of 18, and it was once a very serious childhood disease. Before effective treatments became available it often led to rheumatic fever and death, but the availability of antibiotics has dramatically reduced the scarlet fever mortality rate.
Scurvy is a disease caused by a vitamin C deficiency. Symptoms of scurvy include weakness, anemia, gum disease, and bleeding from the mucus membranes. The disease was once common among sailors who were at sea for long periods without access to fresh fruit. When it became widely known that citrus fruits (with their abundant vitamin C) could prevent scurvy, sailors began taking lemon juice on long voyages and incidences of scurvy diminished greatly. Cases of scurvy in the U.S. are now rare, but the disease occasionally appears in older, malnourished adults.
For more information, see “Scurvy,” from Medline Plus Medical Encyclopedia.
Smallpox is a serious, contagious, and sometimes fatal infectious disease caused by a virus. There is no specific treatment for smallpox disease, and the only prevention is vaccination. The name smallpox is derived from the Latin word for “spotted” and refers to the raised bumps that appear on the face and body of an infected person.
To learn more, read the article “Smallpox” from LEARN NC’s North Carolina digital history textbook.
Typhoid fever is a bacterial infection caused by Salmonella typhi bacteria. At the onset of typhoid fever, symptoms include fever, malaise, and stomach pain. As the disease progresses, the fever increases to over 103 degrees Fahrenheit and diarrhea begins. Eventually weakness and delirium develop, and in some cases a rash appears on the chest and abdomen.
Salmonella typhi bacteria are spread by contaminated food or water. The bacteria live in the intestinal tracts of infected humans and can enter the food supply as a result of improper hand-washing. Bacteria may also enter the water supply in places where sewage is improperly treated. Typhoid bacteria can live in the intestines of healthy people who carry and spread the disease without ever experiencing symptoms. In New York in 1906, a cook named Mary Mallon was linked to outbreaks of typhoid fever in every town where she worked. Eventually she was tested, and doctors discovered that although Mallon was perfectly healthy, she unknowingly carried the typhoid bacteria. She became notorious as a disease carrier, acquiring the nickname “Typhoid Mary.”
Because of modern sanitation, cases of typhoid fever in the U.S. and other industrialized nations are now rare, but the disease still occurs regularly in nations where sewage treatment is inadequate. In most cases, typhoid fever is not fatal if it is treated with antibiotics, but if left untreated the disease has a mortality rate of 10-30%. The most effective prevention method is proper hygiene and sanitation, but vaccines against the disease are also available.
For more information about typhoid fever, see these articles from the Centers for Disease Control and Prevention’s National Center for Emerging and Zoonotic Infectious Diseases and Medline Plus Medical Encyclopedia. To learn more about “Typhoid Mary,” read this press release from the National Institutes of Health’s National Library of Medicine.
Yellow fever is a viral infection transmitted by mosquitoes that carry the virus. The disease typically occurs in tropical areas, particularly in parts of South America and Sub-Saharan Africa. Before its cause was known, yellow fever was also common in the U.S., and outbreaks killed thousands in port cities, including Philadelphia, New York, Baltimore, Norfolk, and New Orleans. In 1900, U.S. Army physicians made the connection between yellow fever and mosquito bites, and subsequent efforts to control mosquitoes led to a significant decline in yellow fever cases in the U.S. The last epidemic of yellow fever occurred in New Orleans in 1905.
Yellow fever symptoms usually appear three to six days after being bitten by an infected mosquito, and they develop in three stages. In the first stage, symptoms include fever, headache, muscle aches, vomiting, and jaundice. This lasts for three to four days before the second stage — remission — begins. During remission, the fever and other symptoms go away. Most people recover at this stage, but some move on to the third stage — intoxication. This stage is the most serious, and involves liver and kidney failure, bleeding disorders, delirium, coma, and seizures. Yellow fever that reaches this third stage is often fatal. Although individual symptoms can be treated, no effective treatments exist for the disease itself. A vaccine that effectively prevents yellow fever has been widely available since the 1950s.
To learn more about yellow fever, read these articles from the Centers for Disease Control and Prevention and Medline Plus Medical Encyclopedia. For more information about the history of yellow fever in the U.S., see U.S. Army Physicians Discovered the Cause of Yellow Fever, August 27, 1900 from the Library of Congress.