Is the United States really at risk for introduction of Rift Valley fever virus?

Abstract

JAVMA, Vol 242, No. 5, March 1, 2013 R Valley fever continues to garner substantial attention as a potential agricultural and zoonotic disease threat to the United States. It has been stated that “the presence of competent vectors in countries free of RVF, the high viral titers in viremic animals and the global changes in climate, travel and trade all contribute to make this virus a threat that must not be neglected as the consequences of RVF are dramatic, both for human and animal health.” Rift Valley fever virus was first isolated from lambs in the Rift Valley of Kenya in the 1930s. Major outbreaks of RVFV infection have been recorded in many parts of sub-Saharan Africa since that time, and a large outbreak of the disease occurred in Egypt in the late 1970s. The virus was first detected outside the African continent in Saudi Arabia and Yemen in 2000, with the outbreak attributed to the legal importation of cattle and small ruminants from the Horn of Africa. Six viral strains were isolated from Aedes mosquitoes during this outbreak, and all were phylogenetically related to strains isolated in Kenya in 1997. The aim of the present commentary is to qualitatively assess the threat of introduction of RVFV in nonendemic regions, particularly the United States.