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.
Toribio ML, de la Hera A, Borst J, Marcos MA, Márquez C, Alonso JM, Bárcena A, Martínez C.Toribio ML, et al.J Exp Med. 1988 Dec 1;168(6):2231-49. doi: 10.1084/jem.168.6.2231.J Exp Med. 1988.PMID: 2848921Free PMC article.