Actually, we do not know what causes most cases of breast cancer.
Nuclear waste, we are told, caused many deaths and cases of cancer.
In fact we don't yet understand the human mind well enough to say for sure exactly what causes most cases of amnesia.
But it probably causes more cases of disease than any of the other three.
Doctors don't know exactly what causes most cases of childhood leukemia.
The measures stopped the virus after it caused 8,098 cases, including 774 deaths, this year.
The outbreak caused 10 deaths and more than 50 cases of infection.
The incident is thought to have caused 6,000 extra cases of thyroid cancer in people who were children at the time.
But why they cause so few cases among the estimated 35 million soft lens users in this country is a mystery.
The mystery is especially compelling because scientists do not know what causes most cases of Parkinson's.
