Coronary Artery Disease (Ischemic Heart Disease)

The deadliest disease in the world is coronary artery disease (CAD). CAD, also called ischemic heart disease, occurs when the blood vessels that supply blood to the heart become narrowed. The World Health Organization (WHO) estimates that about 7.4 million people died of ischemic heart disease in 2012. That was about 13.2 percent of all deaths.

In the United States, about 600,000 people die of heart disease every year, according to the Centers for Disease Control and Prevention (CDC). That makes it the deadliest disease in the U.S., as well as the world. In the U.S. the most common type of heart disease is CAD, which takes about 380,000 lives each year.

Among the risk factors are high blood pressure, high cholesterol, and smoking. Regular exercise, good nutrition, and weight control can help lower your risk of developing CAD.

Where you live matters. Although it’s still the leading cause of death, mortality rates have declined in many European countries and in the United States. This may be due to better prevention and access to quality healthcare. However, in many developing nations, mortality rates due to CAD are on the rise.


Diabetes

Diabetes is a group of diseases that affect insulin production and use. In type 1 diabetes, the pancreas can no longer produce insulin. The cause is not known. In type 2 diabetes, the pancreas doesn’t produce enough insulin, or it can’t be used effectively. Type 2 diabetes can be caused by a number of factors, including poor diet, lack of exercise, and carrying too much weight.

In 2012, about 1.5 million people died from diabetes-related causes, according to WHO. People in low to middle income countries are more likely to die from complications of diabetes.


Cancer

Cancer is the name given to a collection of related diseases. In all types of cancer, some of the body’s cells begin to divide without stopping and spread into surrounding tissues.Cancer can start almost anywhere in the human body, which is made up of trillions of cells. Normally, human cells grow and divide to form new cells as the body needs them. When cells grow old or become damaged, they die, and new cells take their place.

When cancer develops, however, this orderly process breaks down. As cells become more and more abnormal, old or damaged cells survive when they should die, and new cells form when they are not needed. These extra cells can divide without stopping and may form growths called tumors.Many cancers form solid tumors, which are masses of tissue. Cancers of the blood, such as leukemias, generally do not form solid tumors.


Arthritis

Arthritis is very common but is not well understood. Actually, “arthritis” is not a single disease; it is an informal way of referring to joint pain or joint disease. There are more than 100 different types of arthritis and related conditions. People of all ages, sexes and races can and do have arthritis, and it is the leading cause of disability in America. More than 50 million adults and 300,000 children have some type of arthritis. It is most common among women and occurs more frequently as people get older.

Common arthritis joint symptoms include swelling, pain, stiffness and decreased range of motion. Symptoms may come and go. They can be mild, moderate or severe. They may stay about the same for years, but may progress or get worse over time. Severe arthritis can result in chronic pain, inability to do daily activities and make it difficult to walk or climb stairs. Arthritis can cause permanent joint changes. These changes may be visible, such as knobby finger joints, but often the damage can only be seen on X-ray. Some types of arthritis also affect the heart, eyes, lungs, kidneys and skin as well as the joints.


STDs

Sexually transmitted diseases (STDs) are caused by infections that are passed from one person to another during sexual contact.These infections often do not cause any symptoms. Medically, infections are only called diseases when they cause symptoms. That is why STDs are also called "sexually transmitted infections." But it’s very common for people to use the terms "sexually transmitted diseases" or "STDs," even when there are no signs of disease.

There are many kinds of sexually transmitted diseases and infections. And they are very common — more than half of all of us will get one at some time in our lives. Use the list above to find out about each kind of STD.The good news is we can protect ourselves and each other from STDs. Practicing safer sex allows you to reduce your risk of getting sexually transmitted diseases. And if you've done anything that puts you at risk of infection, getting tested allows you to get any treatments you may need.


High Blood Pressure

High blood pressure (hypertension) can quietly damage your body for years before symptoms develop. Left uncontrolled, you may wind up with a disability, a poor quality of life or even a fatal heart attack. Roughly half the people with untreated hypertension die of heart disease related to poor blood flow (ischemic heart disease) and another third die of stroke.

Treatment and lifestyle changes can help control your high blood pressure to reduce your risk of life-threatening complications.Here's a look at the complications high blood pressure can cause when it's not effectively controlled.

High blood pressure can damage the cells of your arteries' inner lining. When fats from your diet enter your bloodstream, they can collect in the damaged arteries. Eventually, your artery walls become less elastic, limiting blood flow throughout your body


Blood and Immune System

Your immune system is your body’s defense against infections and other harmful invaders. Without it, you would constantly get sick from bacteria or viruses.Your immune system is made up of special cells, tissues, and organs that work together to protect you.

The lymph, or lymphatic, system is a major part of the immune system. It's a network of lymph nodes and vessels. Lymphatic vessels are thin tubes that branch, like blood vessels, throughout the body. They carry a clear fluid called lymph. Lymph contains tissue fluid, waste products, and immune system cells. Lymph nodes are small, bean-shaped clumps of immune system cells that are connected by lymphatic vessels. They contain white blood cells that trap viruses, bacteria, and other invaders, including cancer cells.White blood cells are the cells of the immune system. They are made in one of your lymph organs, the bone marrow. Other lymph organs include the spleen and thymus.

Severe combined immunodeficiency (SCID). This is an example of an immune deficiency that is present at birth. Children are in constant danger of infections from bacteria, viruses, and fungi. This disorder is sometimes called “bubble boy disease.” In the 1970s, a boy had to live in a sterile environment inside a plastic bubble. Children with SCID are missing important white blood cells.


Brain and Nervous System

The nervous system is a complex collection of nerves and specialized cells known as neurons that transmit signals between different parts of the body. It is essentially the body’s electrical wiring.

tructurally, the nervous system has two components: the central nervous system and the peripheral nervous system. According to the National Institutes of Health, the central nervous system is made up of the brain, spinal cord and nerves. The peripheral nervous system consists of sensory neurons, ganglia (clusters of neurons) and nerves that connect to one another and to the central nervous system.

Functionally, the nervous system has two main subdivisions: the somatic, or voluntary, component; and the autonomic, or involuntary, component. The autonomic nervous system regulates certain body processes, such as blood pressure and the rate of breathing, that work without conscious effort, according to Merck Manuals. The somatic system consists of nerves that connect the brain and spinal cord with muscles and sensory receptors in the skin.


Infectious and Parasitic

Parasites are organisms that live off other organisms, or hosts, to survive. Some parasites don’t noticeably affect their hosts. Others grow, reproduce, or invade organ systems that make their hosts sick, resulting in a parasitic infection.

The symptoms of parasitic infections vary depending on the organism. For example:

  • Trichomoniasis is a sexually transmitted infection caused by a parasite that often produces no symptoms. In some cases, it may cause itching, redness, irritation, and an unusual discharge in your genital area.
  • Giardiasis may cause diarrhea, gas, upset stomach, greasy stools, and dehydration.
  • Cryptosporidiosis may cause stomach cramps, stomach pain, nausea, vomiting, dehydration, weight loss, and fever.
  • Toxoplasmosis may cause flu-like symptoms, including swollen lymph nodes and muscle aches or pains that can last for over a month.

Inherited Diseases

Although genetic factors play a part in nearly all health conditions and characteristics, there are some conditions in which the genetic changes are almost exclusively responsible for causing the condition. These are called genetic disorders, or inherited diseases.Since genes are passed from parent to child, any changes to the DNA within a gene are also passed. DNA changes may also happen spontaneously, showing up for the first time within the child of unaffected parents. This is referred to as a new mutation, where the word mutation means change.

Sometimes this change can cause mistakes in the protein instructions, leading to production of a protein that doesn't work properly or cannot be made at all. When one protein is missing or not working as it should, it can cause a genetic disorder.The genetics of each disorder are unique. In some cases, all the mistakes in a particular gene cause one specific genetic disorder. In other cases, different changes within the same gene can lead to different health or developmental problems or even to different genetic disorders. Sometimes changes in several similar genes may all lead to the same genetic disorder.