Since the West Nile virus first appeared in the U.S. in 1999, it has spread to every state in the country.

Deaths from West Nile are most common in birds and horses, but dogs, cats, wild mammals and people can also be infected. The disease is spread as mosquitoes feed on infected birds, then on other animals or people. The virus targets the central nervous system, causing neurologic problems like stumbling, circling, difficulty standing and paralysis in animals. Thankfully, the disease usually runs its course in cats and dogs without treatment.

West Nile vaccines are only available for horses. Prevention includes avoiding mosquitoes by staying inside during dusk and dawn. Eliminating standing water can help squelch mosquito breeding. There’s even pet-specific mosquito repellant; just be sure to avoid DEET-based products, as they are toxic when ingested.