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 solid arrows represent flow between compartments and dotted arrows represent the additive contribution relationship to a compartment. Infectious individuals are split into symptomatic and asymptomatic individuals. For symbols used refer to Table 1.
