Which of the following icons is used to represent a male affected with a disease?

A half-filled circle

A half-filled square

A completely filled circle

A completely filled square

The answer is a completely filled square, due to the fact that a circle represents female so generically a square would be male. An empty shape has no traces of the disease, half filled shape is a carrier of said disease, and fully filled shape has the disease.

I believe a completely filled square represents a male affected with a disease.

A half-filled circle represents a carrier female, while a a half filled square represents a carrier male and a completely filed circle represents an infected female with a disease. Normally these are shown in a human pedigree which shows the occurrence an appearance or phenotype of a particular gene or organisms and its ancestors from one generation to the next.