Diseases 
How many diseases are there in the world?
There are four main types of disease: infectious diseases, deficiency diseases, hereditary diseases (including both genetic diseases and non-genetic hereditary diseases), and physiological diseases.
How many rare diseases are there in the world?
There are between 5 000 and 8 000 rare diseases, most of them with a genetic basis. 1 A very rough estimate would be that one out of 15 persons worldwide could be affected by a rare (“orphan”) disease – 400 million people worldwide, of whom 30 million are in Europe and 25 million in the United States.
What are the 10 most common diseases?
- Unintentional injuries.
- Chronic lower respiratory disease.
- Stroke and cerebrovascular diseases.
- Alzheimer’s disease. Deaths in 2017: 121,404.
- Diabetes. Deaths in 2017: 83,564.
- Influenza and pneumonia. Deaths in 2017: 55,672.
- Kidney disease. Deaths in 2017: 50,633.
- Suicide. Deaths in 2017: 47,173.
What are the most common diseases in the world?
So, without further ado, here are the five most common infectious diseases.
- Hepatitis B. According to current statistics, hepatitis B is the most common infectious disease in the world, affecting some 2 billion people — that’s more than one-quarter of the world’s population.
- Malaria.
- Hepatitis C.
- Dengue.
- Tuberculosis.