Isaac wants to know how quickly the hiv/aids virus is spreading among teenagers. when conducting his research, he will want to look at the number of new cases, of the of the disease.

Incidence

Explanation:

Isaac will need to assess the incidence rate of HIV-infected adolescents for his research. This must be done because Isaac's research wants to gauge the speed with which this virus is spreading among teens. For this, Isaac must make a comparison between the existing number of patients who fit this case, with patients who fit the recent cases of incidence of the disease. That is, when conducting his research, he will want to examine the number of new cases, the incidence of the disease.