According to a report from the Center for Disease Control, the West Nile Virus appears to hardly cause illness in dogs and cats.

Infectious mosquitoes that can be fatal to humans transmit the WNV. Dogs and cats could be exposed to the same virus when bitten. A very small number of dogs, less than 40, have been reported to being infected with no symptoms experienced. A study about experimentally infected dogs showed no symptoms. Cats might experience mild symptoms during the first week after an infection, such as slight fever to slight lethargy.

An undocumented report states that dogs and cats might become infected when eating dead, infected birds. It is most unlikely that pet owners would even notice any unusual behavior in cats and dogs after becoming infected with WNV. No specific treatment is available for WNV, though you should take your animal to the veterinarian in case of any symptoms of a viral infection; another virus could have caused the infection.

There are also no indications that infected cats or dogs might transmit the disease to humans. It’s also unlikely that cats and dogs will become carrier of this virus and infect more mosquitoes when bitten, the bloodstream of infected dogs does not carry a high enough level of virus. The level in cats might be slightly higher but there is no evidence that a cat might infect mosquitoes either.