Stocks of the virus are maintained since 1990 by the USA and the USSR. An agreement to destroy stocks, mainly for security reasons, was never effected. The members of the World Health Organization have voted for the destruction of remaining stocks in June 1999. In the meantime, genetic studies of the smallpox virus have encouraged certain scientists to argue for its preservation, as a genetic library from which humans can gain a wealth of knowledge about human disease and resistance to disease.