Doctors could do little since neither its cause nor transmission were understood.

The cause and progression of Alzheimer's disease are not well understood.

The causes of the errors are not yet well understood.

However, the exact cause of the disease is not well understood.

'The cause of her flight is too well understood,' I said.

The cause and role of this increase is poorly understood.

Though the cause of the fever was not understood, many theories existed.

In most cases, the cause of this birth defect is not fully understood.

The environmental causes of health problems are complex, global, and poorly understood.

The first cases were identified in 1997 and its cause is not fully understood.