The true incidence of such reporting cannot be determined.

And the true incidence in Latin America is much higher, officials said.

But it has been difficult to determine the true incidence of the disease because only its severe form is clearly recognized.

The true incidence of thromboembolism in this procedure is not known.

Since this is a newly identified condition that is just being described, we cannot know its true incidence.

The true incidence is difficult to determine, pain having a subjective component.

"I don't think the true incidence is 1 percent," she said.

Therefore, our data cannot show the true incidence.

And, as with all venereal diseases, the reported cases are thought to represent only a fraction of the true incidence.

The true incidence is unknown, but is estimated at 1:25,000 live births.