Which pattern of infection would be predicted in a biowarfare attack with an alphavirus?

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Alphaviruses are mosquito-borne viruses, so their spread in an outbreak depends on how the virus moves between people, horses, and other animals via mosquitoes. In a biowarfare release, people are most likely to be exposed directly and become ill first. Once people are infected, local mosquitoes can bite them and become carriers, potentially passing the virus to other susceptible hosts. Horses are particularly susceptible to alphavirus infections and tend to develop high levels of virus in the blood, making them efficient amplifying hosts. As the virus circulates among humans and horses, it can continue to involve other wildlife, such as rodents, helping to establish and sustain the enzootic transmission cycle in the environment. So the pattern you’d expect is humans affected first, then equines, and then rodents, reflecting the way alphaviruses spread through a mosquito-driven cycle with horses as prominent amplifying hosts and rodents as part of the maintained reservoir.