Updated: 26.02.2020
Diseases and Medical Conditions
A
disease is a particular abnormal condition, a disorder of structure or function, that affects part or all of an organism. The study of diseases is called pathology. A disease is often constructed as a medical condition associated with specific symptoms and signs. It may be causes by external factors such as pathogens, or by internal dysfunctions, particularly of the immune system. There are four main types of disease, infectious disease, deficiency disease, genetic disease (hereditary and non-hereditary) and physiological diseases.
In a broader sense, disease includes injuries, disabilities, disorders, syndromes, isolated symptoms, deviant behaviors and atypical variations of structure and function. Death due to disease is called death by natural causes. A
disorder is a functional abnormality or disturbance, such as a mental disorder which is a complex interaction of biological, social and psychological factors. A
medical condition is a broad term that includes everything that normally receives medical treatment. A
syndrome is the association of several medical sighs, symptoms and other characteristics that occur together and can have different causes.
There are several causes of disease. An
airborne disease is any disease that is caused by pathogens and transmitted through the air. Foodborne illness or
food poisoning is any illness resulting from the consumption of food contaminated with pathogenic bacteria, viruses, toxins, prions or parasites.
Infectious diseases, also called transmittable, contagious or communicable, are illnesses resulting from infection, it can spread from one person to another. A
lifestyle disease is any disease that appears to increase in frequency in industrialized countries, the risk factors include sedentary lifestyle, unhealthy foods and pollution. A
non-communicable disease is a medical condition that is non-transmissible, such as heart disease or cancer.
An
acquired disease is one that began at some point during one's life, at any time after birth. A
genetic disease or disorder is caused by genetic mutation and is often inherited. So, an inherited or
hereditary disease is a type of genetic disease caused by mutations that usually run in the family. An
acute disease is one of a short-term nature, it can have a sudden onset and be severe. On the other hand, a
chronic disease or condition is one that persists over time, usually for at least six months, and can last for the rest of the patient's life.
An
idiopathic disease has an unknown cause or source. An
incurable disease cannot be cured, but sometimes the symptoms can be treated. A
terminal disease is one that is expected to have the inevitable result of death. A
progressive disease typically worsens over time until a serious state, organ failure and death. On the other hand, a stable or
static disease does not get better or worse. A
systemic disease affects the entire body. On the other hand, a
localized disease affects only one part of the body. A
primary disease is due to a root cause of illness. On the other hand, a
secondary disease is a sequella or complication.
Many diseases and disorders can be prevented through a variety of means, these include sanitation, proper nutrition, adequate exercise, vaccinations and other self-care and public health measures.
Diseases that Cause most Deaths Worldwide
Historically, the deadliest disease ever by estimated death toll was the plague. The
Black Death, caused by the bacterium Yersinia pestis, killed something from 75 to 200 million people between 1331 and 1353, which at that time was 30 to 60% of the world's population. The plague struck in Europe, Asia and North Africa and was perhaps the most devastating pandemic in human history.
Spanish Flu, a pandemic from 1918 to 1920, infected about 500 million people around the world. The result was from 50 to 100 million dead people, more than WWI.
The statistics of deadliest diseases change over time, as medicine progresses. Several of the deadliest diseases are preventable, just like many risk factors to almost all main diseases. As healthcare progresses, causes and cures for many diseases are discovered. An increasing life span naturally leads to an increase in some health conditions. By mortality rates, the most dangerous are cardiovascular diseases with about 17,6% of cases, the second deadliest are infections and parasitic diseases and the third is cancer.
Today, the deadliest disease in the world is coronary artery disease, also called
ischemic heart disease. It occurs when the blood vessels that supply blood to the heart become narrowed. It can lead to chest pain, arrhythmias and heart failure, causing 15,5% deaths worldwide. The risk factors include high blood pressure, high cholesterol, smoking, diabetes, being overweight and family history of the disease.
The second deadliest medical condition is a
stroke, it causes 11,1% deaths worldwide. It occurs when an artery in the brain is blocked or leaks and causes the death of the oxygen-deprived brain cells within minutes. During a stroke, the patient can feel sudden numbness and confusion, have trouble walking and seeing. If left untreated, it can lead to long-term disabilities, patients should receive treatment within 3 hours of having a stroke. The risk factors include high blood pressure, smoking, being female, and family history of stroke.
The third most deadliest diseases are
lower respiratory infections which cause 5,7% deaths worldwide. These diseases include mainly influenza, pneumonia, bronchitis and tuberculosis. The main symptom is coughing, but also breathlessness, wheezing and a tight feeling in the chest. The risk factors include poor air quality or frequent exposure to lung irritants, smoking, a weak immune system and asthma.
The fourth disease to cause most deaths worldwide is
chronic obstructive pulmonary disease, about 5,6% of deaths. It is a long-term, progressive lung disease that makes breathing difficult. Chronic bronchitis and emphysema are types of this disease. Risk factors include smoking, lung irritants and family history of respiratory diseases. There is no cure but its progression can be slowed with medication.
Respiratory cancers cause about 3% of deaths worldwide. They include the cancer of the trachea, larynx, bronchus and lungs. The main causes are smoking and secondhand smoke, environmental toxins and household pollutions, such as solid fuel emissions and mold.
Diabetes is a group of diseases that affect insulin production and use, these cause about 2,8% deaths worldwide. Risk factors include excess body weight, high blood pressure, older age, not enough exercise and an unhealthy diet.
Alzheimer's disease and other dementias cause 2,7% of deaths worldwide. Alzheimer's is a progressive disease that destroys memory and interrupts normal mental functions, including reasoning and typical behavior. From 60% to 80% cases are Alzheimer's disease, it is the most common type of dementia. It starts off by causing mild memory problems, but progresses. The risk factors include being older than 65, a family history of dementia, Down syndrome, unhealthy lifestyle, being female, previous head trauma and being socially isolated.
Dehydration due to diarrheal diseases causes 2,5% of deaths worldwide. Lasting diarrhea can cause dehydration which can lead to death. It is usually caused by an intestinal virus or bacteria transmitted through contaminated water or food. It is the second top cause of death in children younger than 5 years. Risk factors include poor sanitary conditions, no access to clean water, malnourishment, a weakened immune system and being a young child.
Tuberculosis causes 2,4% of deaths worldwide. It is a lung condition caused by bacteria called Mycobacterium tuberculosis, a treatable airborne bacterium. It is preventable by vaccination and most of the serious cases are from developing countries, because it spreads quickly among people who are malnourished and in overcrowded conditions. It is one of the top causes of death in people with HIV, about 35%. The risk factors include diabetes, HIV infection, a lowed body weight, proximity to others with tuberculosis and regular use of medications like corticosteroids and immunosuppressants.
The tenth deadliest disease is
cirrhosis which causes 2.1% of deaths worldwide. It is a result of chronic scarring and damage to the liver, caused by a kidney disease, conditions like hepatitis or chronic alcoholism. Risk factors include chronic alcohol abuse, fat accumulation around the liver and chronic viral hepatitis. Healthy diet low on sugar and fat can prevent the disease.
Deadliest Diseases
Some diseases are so dangerous that contracting the disease almost inevitably leads to death.
African trypanosomiasis, simply called
sleeping sickness, is an insect-borne parasitic disease. The symptoms are fevers, headache, itchiness and joint pain, and later trouble sleeping, confusion and poor coordination. Treatment is easier before neurological symptoms occur, without treatment the patient most surely dies.
Rabies is a viral disease that causes inflammation of the brain. Symptoms include fever, fear of water, confusion, excessive salivation, violent movements, hallucinations, trouble sleeping, paralysis and coma. Once symptoms appear, the result is nearly always death. Vaccination after exposure is highly successful in preventing the disease, in unvaccinated humans, rabies is almost always fatal after neurological symptoms have developed. In 2003, Jeanna Giese became the first person known to survive rabies after symptom onset.
Smallpox is an infectious disease caused by two viruses, Variola major and Variola minor. The last naturally occurring case was diagnosed in 1977 and the WHO certified the global eradication of the disease in 1980. The untreated disease was almost always deadly, the death risk of treated patients was about 30%, with higher rates among babies. Survivors had extensive scarring of skin and some were left blind. Early symptoms are fever, vomiting and mouth sores, later symptoms are fluid filled blisters which scab over. This disease is estimated to have killed up to 300 million people in the 20th century. Vaccination was discovered in 1798 by Edward Jenner and smallpox became one of two infectious diseases to have been eradicated.
Human immunodeficiency virus
HIV and acquired immune deficiency syndrome
AIDS do not cause death by themselves, but they make humans unable to fight off diseases and the patient usually dies of common respiratory infections. HIV is spread by unprotected sex, contaminated blood transfusions, hypodermic needles and from mother to child. It is a retrovirus and there is no cure or vaccine. However, antiretroviral treatment can slow the course of the disease and may lead to near-normal life expectancy. Without treatment, the average survival time after infection is 11 years. Globally, about 37,9 million people are HIV positive, including 1,7 million children, and around 21% of these do not know that they have the virus.
Ebola is a viral hemorrhagic fever caused by ebolavirus. Symptoms include fever, muscular pain, sore throat and headaches, followed by vomiting, diarrhea and rash with decreased function of the liver and kidneys. It is highly deadly and from 25% to 90% of infected patients die, with an average of about 50%.
Influenza is an viral infectious disease of the upper respiratory tract that can be mild to severe. Most common symptoms include high fever, runny nose, sore throat, weakness, muscle and joint pain, headache, shivering, coughing and feeling tired. Stomach flu usually involves diarrhea, vomiting and loss of appetite. Humans are affected by types A, B and C and its yearly outbreaks result up to 5 million severe cases and up to 650 thousand deaths. It cannot be cured by antibiotics, they are prescribed to fight off a secondary bacterial infection. Death occurs mostly in high risk groups, the young, the old and those with other health problems. Most transmissions occur through hand-to-hand contact, so sanitation prevents infection. Since the 20th century, four pandemics have occured, in 1918, 1957, 1968 and 2009.
Tetanus, also called lockjaw, is a bacterial infection characterised by muscle spasms that can be severe enough to cause bone fractures. Recovery may take month and about 10% of cases become fatal, unvaccinated and untreated cases have a 50% chance of survival. It can be prevented by immunization with tetanus vaccine and in 2015 the disease killed 59 thousand people.
Tuberculosis is an infectious disease usually caused by Mycobacterium tuberculosis. It is the leading cause of death around the world for an infectious disease. About a quarter of human population is thought to be infected, but most people have a latent form and they do not spread the disease. It is preventable by vaccination and most of the serious cases are from developing countries. The risk factors include diabetes, HIV infection, a lowed body weight, proximity to others with tuberculosis and regular use of medications like corticosteroids and immunosuppressants.
Diseases of Affluence - Diseases of Rich People - Civilisation Diseases
Diseases and health conditions of affluence are commonly thought to be a result of wealth in society. They occur more and more since the end of WWII. Examples of these diseases are mostly chronic non-communicable diseases and other conditions associated with lifestyle and social conditions. They include diabetes, asthma, ischemic heart disease, stroke, dementia, obesity, hypertension, cancer, alcoholism, gout, allergy, depression, mental illness and other mental health conditions.
These diseases are a direct result of technological advances which lead to less physical exercise and an unhealthy diet. The life of modern people is less physically demanding and people exercise irregularly or not at all. Food is easily accessed and cheap fastfood is preferred. People consume more fat, meat, dairy and sugar if foods which are pre-prepared, processed and commercially provided. Tabacco and alcohol are abused frequently. Longer lifespans mean that more diseases have time to occur and increased cleanliness leads to increased occurrence of allergy and autoimmune diseases.
Obesity
It is the most wide-spread civilisation disease of our time. It is a medical condition in which excess body fat has accumulated to an extent that it may have a negative effect on health. People are considered obese when their BMI (body mass index) is over 30. It is more common in women than men and carries social stigma.
In many countries there are over 30% obese people which is a big problem for the healthcare system. It is the leading preventable cause of death worldwide. It increases the risk of various diseases, especially heart problems, type 2 diabetes, some types of cancer and problems with the musculoskeletal system.
It is mainly caused by lifestyle, unhealthy diet, overeating and not enough physical activity. A few cases are caused by genes, endocrine disorders, medication or psychiatric illnesses. This condition is mostly preventable through a combination of social changes and personal choices, especially changes to diet and exercising.
The basic treatment are dieting and physical exercise. In serious cases of failure of basic treatment anti-obesity medication and surgery can be recommended to reduce appetite.
Cancer
It is a disease where groups of cells show abnormal and uncontrolled growth, destroy adjacent tissues and sometimes metastaze or spread to other locations in the body via lymph or blood. There are malignant and benign tumors that do not metastaze. Over a hundred types of cancer affect humans, the most common cancer types are lung, breast and prostate, skin, stomach and colorectal cancer.
Common environmental factors leading to cancer include smoking, unhealthy diet and obesity, lack of physical activity and environmental pollutants. From 5 to 10% of cancers are due to inherited genetic defects.
Most types of cancer can be treated, this includes chemotherapy, radiotherapy and surgery. Cancer can affect people of all ages and a few types are more common in children, like leukemia. Generally the risk of developing cancer increases with age and many cancers occur more commonly in developed countries.
Gout
Gout is a form of inflammatory arthritis characterized by recurrent attacks of a red, tender, hot and swollen joint. It occurs due to persistently elevated levels of uric acid in the blood. At high levels, the acid crystallizes and deposits in joints, tendons and surrounding tissues, resulting in an attack.
This disease occurs due to a combination of diet, other health problems and genetic factors. It occurs more commonly in those who regularly eat meat or seafood, drink beer and are overweight. From 1 to 2% of the Western population is affected by gout. Older males are most commonly affected and it was once known as the disease of kings.
Am attack can be treated by medication that improves the symptoms. Medication and lifestyle changes are used for further prevention. Healthier diet should reduce purine-rich food and fructose.
Alcoholism
Alcohol abuse disorder is a broad term for any drinking of alcohol that results in mental or physical problems. This can affect all parts of the body, but particularly the brain, heart, liver, pancreas and immune system. It can result in mental illness, irregular heartbeat, liver cirrhosis, increased cancer risk and other health conditions. Alcoholism also reduces life expectancy by around ten years.
Women are generally more sensitive to harmful effects of alcohol, but men abuse alcohol more commonly. The World Health Organization estimates that there are over 4% of alcoholics worldwide, in the USA it is 7% and in Eastern Europe, it is 11%.
Mental Illness
One in four people have experienced mental illness in their lives. China and the US are the countries with the highest levels of anxiety, depression and schizophrenia, the US is reported to have the highest level of depression worldwide. From 2% to 6% of people worldwide have depression, the same goes for anxiety disorders.
A mental illness or a psychiatric disorder is a behavioral or mental pattern that causes significant distress or impairment or personal functioning. The causes are often unclear.
Depression, major depressive disorder, is a mental disorder characterised by at least two weeks of low mood that is present across most situations.
Anxiety is an emotion characterised by an unpleasant state of inner turmoil, often accompanied by nervous behaviour.
Suicide is the act of killing oneself, sometimes it is impulsive, but many are premeditated. It is the tenth leading cause of death worldwide, causing death of 1,5% of people. Men are more likely to kill themselves, it is most common in people over 70, but in some countries people between 15 and 30 are at the highest risk. There are an estimated 10 to 20 million non-fatal attempted suicides every year. Attempted suicide is more common among young people and women.
Allergy and Autoimmune Diseases
The rate of allergies around the world has risen in industrialized nation since WWII. It is assumed that there are less allergies and autoimmune diseases in developing countries than in developed countries. A number of public health measures, such as sterilized milk, use of antibiotics and improved sanitation may have contributed to that.
An
allergy is a condition caused by hypersensitivity of the immune system to typically harmless substances in the environment. Food allergy is an immune reaction caused by the release of histamine, it is immediate.
Food intolerance is a detrimental reaction, often delayed, that produces symptoms. It is a result of the absence of specific chemicals and enzymes needed to digest a food substance and it can be hereditary.
Autoimmunity is the system of immune responses against its own healthy cells and tissues. There are at least 80 types of autoimmune diseases and the cause is generally unknown, some may be hereditary. Women are more commonly affected and in the US, about 7% of people are affected. The first autoimmune diseases were described in the early 1900s.
Diseases of Poverty - Diseases of Poor People
On the other hand,
diseases of poverty are mostly infectious diseases or conditions which are the result of poor living conditions. These include tuberculosis, malaria, asthma, conditions related to malnutrition and poor health behaviour and HIV. Poor developing countries and regions are most affected. Risk factors include poor housing and working conditions, inadequate sanitation, exposure to sick people, malnutrition, contaminated water, stress, overwork, inadequate education, and minimal health care.
Neglected tropical diseases are a diverse group of tropical infections which are common in low-income populations in developing regions. These diseases affect more than 1,4 billion people but are underfunded, although some treatments are relatively inexpensive. The combined total number of death due to these diseases is comparable to malaria and tuberculosis.
Tuberculosis, an infectious disease usually caused by Mycobacterium tuberculosis, is the leading cause of death around the world for an infectious disease. It is especially spread in sub-Saharan Africa, Latin America and the Caribbean region. It spreads quickly among people who are malnourished and in overcrowded conditions. It is preventable by vaccination and most of the serious cases are from developing countries. The risk factors include diabetes, HIV infection, a lowed body weight, proximity to others with tuberculosis and regular use of medications like corticosteroids and immunosuppressants.
AIDS, acquired immune deficiency syndrome, is most spread in eastern and southern Africa, less in western and central Africa. The disease is caused by HIV, human immunodeficiency virus. Globally, about 37,9 million people are HIV positive, including 1,7 million children, and around 21% of these do not know that they have the virus. It is spread by unprotected sex, contaminated blood transfusions, hypodermic needles and from mother to child. The disease was first clinically reported on June 5, 1981 in the US and it is believed to originate from primates in Africa. The disease makes humans unable to fight off diseases and the patient usually dies of common respiratory infections. It is a retrovirus and there is no cure or vaccine. However, antiretroviral treatment can slow the course of the disease and may lead to near-normal life expectancy. Without treatment, the average survival time after infection is 11 years.
Malaria
Malaria is a mosquito borne infectious disease that causes fever, tiredness, vomiting and headaches, and in severe cases yellow skin, seizures, coma and death. It is caused by single-celled microorganisms of the Plasmodium group and mostly spread by an infected female Anopheles mosquito. Five species can infect humans and most deaths are caused by Plasmodium falciparum.
No effective vaccine exists and it is treated by antimalarial medication, usually in combination. The disease is widespread in tropical and subtropical regions around the equator. In 2018, there were 228 million cases of malaria worldwide, resulting in an estimated 405 thousand deaths, mostly in Africa.
Childhood Diseases
Children have maturing immune systems and are often together is classrooms or on school buses. This makes the transmission of contagious diseases particularly easy and explains why these diseases are so common in children. Contagious diseases are often caused by the spread of bacteria, such as scarlet fever, or viruses such as chickenpox. Diseases of young children include measles and tetanus. Diseases of older children include chickenpox, the fifth disease, mononucleosis, mumps, polio, rubella, scarlet fever and many others.
Chickenpox
Chickenpox, also known as varicella, is a highly contagious disease, that usually affects children. It is caused by VZV, varicella zoster virus. The infection spreads through fluids from the airways, such as from coughing and sneezing. The incubation period is 14-16 days, and the first sign of disease is a rash, small, itchy blisters which scab over and cannot be scratched because it will scar. Other symptoms include fever, tiredness and headaches. The most common complication is infection of lesions with bacteria. Rare complications include lung infection pneumonia or brain infection encephalitis. The disease is often more serious in adults than in children.
Measles
Measles is a highly contagious infection of the respiratory system that is caused by an airborne virus. The incubation period after the virus infects the upper respiratory tract is about 10 days. This child then has 3-4 days of cold-like symptoms, followed by a rash. The child is usually well after 2 weeks of illness and then has life-long immunity to the disease. Complications more commonly occur in children aged younger than 5 and adults older than 20. Serious complications of measles include blindness, inflammation of the brain caused by infection encephalitis, severe diarrhea that may lead to dehydration, ear infections and severe respiratory infections. The most common cause of death associated with measles is from pneumonia. The majority of deaths from measles occur in developing countries. Vaccination resulted in 80% decrease in deaths from measles since 2000.
Scarlet Fever
Scarlet fever is an infection with a type of bacteria called streptococcus which causes a throat infection and also produces a poison causing the distinctive rash. Some people are more sensitive to the toxin so not everyone will have the rash even if they have the throat infection. Incubation is 1-5 days. Symptoms are sore throat and vomiting. There are painful swollen glands in the neck. There is no rash on the face but flushed cheeks. The rash disapears within a week. Antibiotics are usually given for the disease. It is important to keep the child at home and avoid contact with other children. An untreated case may have peeling of the skin. It is contagious to people who come into close contact with an infected child. Complications are rare but can include deeper tissue infections, rheumatic fever and kidney disease.
Mononucleosis
Mononucleosis is an illness caused by the Epstein-Barr virus EBV which is spread through saliva. The most typical symptom is tiredness and sleepiness, combined with swollen lymph glands and spleen, sore throat, fever, loss of appetite and muscle aches. Many people have mild symptoms and don't know they were infected. Because the incubation period is very long, 30 to 50 days, it is almost impossible to avoid the infected. Fortunately, mononucleosis is not very contagious and is usually passed through kissing.
Common Illnesses
Common Cold
Cold is a viral illness which affects the upper respiratory tract. Symptoms include cough, headache, sneezing, sore throat, runny and stuffy nose. It typically lasts up to two weeks, but it is not very serious. Treatment includes cough drops, rest in bed, tea with lemon and drinking a lot of fluids.
Influenza
The flu is a viral infection of the upper respiratory tract. Symptoms are more serious than a common cold, they include fever, sore throat, weakness, muscle and joint pain, shivering, dry cough and severe headache. Stomach flu usually involves diarrhea, vomiting and loss of appetite. It is important to go to see a doctor when the patient has high fever, a persisting cough and sore throat and if the problems last more than 10 days. It cannot be cured by antibiotics, they are prescribed to fight off a secondary bacterial infection. Treatment of flu involves bed rest and drinking a lot of fluids.
Vaccination is possible, but there are many strains of the virus. The person should be vaccinated 6 to 8 weeks before flu season. The virus is contagious during the first three days of illness and the incubation period is one to three days. Most transmissions occur through hand-to-hand contact, so sanitation prevents infection. Humans are affected by types A, B and C and its yearly outbreaks result up to 5 million severe cases and up to 650 thousand deaths. Death occurs mostly in high risk groups, the young, the old and those with other health problems. Since the 20th century, four pandemics have occured, in 1918, 1957, 1968 and 2009.
Conjunctivitis - Pink Eye
It is an inflammation of the transparent membrane that lines the eyelids and part of the eyeballs. It has several possible causes, a bacterial or viral infection, an allergic reaction or it can be a result of chemical irritants.
The bacterial and viral type is highly contagious, so early diagnosis is important. Bacterial cases can be cured with antibiotic eyedrops. Viral conjunctivitis clears up on its own. Patients should try to prevent spreading the infection.
Headache
There are countless of causes of headaches and frequent and severe headaches should be consulted with a doctor. The most common causes of headache include stress, irregular sleep, alcohol abuse, changes in the weather and not enough fluids. Treatment includes ice packs or heating pads, rest, regular exercise and enough fluids.
The three most common types are cluster, tension-type and migraine. A cluster headache affects a specific point of the head and is characterized by sharp and piercing pain. Tension headaches are dull and are usually caused by stress, poor posture and depression. A migraine is a disorder characterised by recurrent headaches that are pulsating and throbbing, and can last up to three days. Other symptoms of a migraine may include nausea, vomiting, sensitivity to light, sound and smell, and some include an aura visual disturbance.
