An official website of the United States government
The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before
sharing sensitive information, make sure you’re on a federal
government site.
The site is secure.
The https:// ensures that you are connecting to the
official website and that any information you provide is encrypted
and transmitted securely.
Chávez-Ayala R, Rivera-Rivera L, Leyva-López A, Sánchez-Estrada M, Lazcano-Ponce E.Chávez-Ayala R, et al.Salud Publica Mex. 2013 Jan-Feb;55(1):43-56. doi: 10.1590/s0036-36342013000100008.Salud Publica Mex. 2013.PMID: 23370258Spanish.