Parainfluenza Types 1-3 National Trends
Participating laboratories report weekly to CDC the total number of parainfluenza types 1-3 tests performed that week, and the number of those tests that were positive. Because reporting delays may be expected for some laboratories, data shown for the more recent weeks may be less complete than others. Each point on the trend graph below displays the average number of parainfluenza types 1-3 tests that were performed nationally, and the average percent of those that were positive from three adjacent weeks: the specified week, and the weeks preceding and following it. This is also known as a centered 3-week moving average.