Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
The frequency of AST events in the U.S. derived from HAEDAT. A-D, five-year frequencies, with the size of the circle denoting the number of events during that interval; E, AST frequencies (events per year) for the entire U.S. (1991 – 2019); F, time series of observed (bars) and modeled (line) proportions of HAEDAT monitoring zones with at least one event. Also reported is the fitted linear logistic model and its significant p value (p<.05).
