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.
Kofod-Olsen E, Ross-Hansen K, Mikkelsen JG, Höllsberg P.Kofod-Olsen E, et al.J Gen Virol. 2008 Jan;89(Pt 1):106-116. doi: 10.1099/vir.0.83224-0.J Gen Virol. 2008.PMID: 18089734