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.
Error bars represent standard deviations. Note: Sample sizes differ between chronic infections. The number of infections depends on sex (P < 0.001).
