Estimating the population proportion of PWID allowed calculation of rates of HIV and HCV infection, which quantifies the disproportionate impact among PWID nationally. Trends from population-based surveys will be monitored as part of CDC's behavioral surveillance analyses and the meta-analysis can be updated as new data emerge. For HIV infection, rates can be calculated on an annual basis with the most recent surveillance data. Other disease metrics can be used to calculate rates, such as HIV incidence [1] or national HIV prevalence estimates [2], which include persons with undiagnosed HIV infection. Because we calculated past year as well as lifetime estimates, others can use either, depending on which best fits their needs. However, our estimates may not be well suited for calculating disease rates at the state or local level as the population sizes of PWID vary across the U.S. [10].
