Rift Valley fever virus: Movement of infected humans threatens global public health and agriculture

Rift Valley fever (RVF) is an acute disease of ungulate livestock and wildlife as well as humans caused by the Rift Valley fever virus (RVFV), which can be transmitted by arthropod vectors such as mosquitoes as well as by direct contact with infected tissues. Outbreaks of this virus may lead to widespread mortality and morbidity in susceptible ungulates and humans, with pronounced economic and agricultural impacts. Humans infected with RVFV can develop extremely high viremias capable of infecting vectors such as mosquitoes. Critically, RVFV has potential for globalization resulting from the movement of infected humans into non-endemic regions containing populations of potentially competent mosquito vectors and susceptible livestock and wildlife hosts that include the US, Asia, and parts of southern Europe. In this review, we explore scenarios of escape of RVFV from its endemic range that could be caused by the movement of infected humans. The risks of globalization of the RVFV pathogen into Europe, Asia, and the Americas is high and increasing each year because of climate change, redistribution and expanding ranges of vector and host species, lack of an approved human vaccine, insecticide resistance, and international travel and commerce. We discuss approaches that could be used to mitigate these avenues of spread that include surveillance targeted by environmental modeling coupled with decisive vector control.