Rift Valley fever is a disease that can infect both humans and livestock, and mosquitoes are one of the main transmitters of the disease. In January 2007, a farm in Ruiru, near Nairobi, Kenya, lost about 80% of its sheep population (right panel) due to a Rift Valley fever outbreak. In January 2016, despite wet conditions and the increase in disease-carrying mosquitos that favored a similar outbreak, the sheep remained healthy (left panel), thanks in large part to early warning and early vaccination. Climate.gov figure modified from photos by K. J. Linthicum and A. Anyamba.