COLUMBUS, Ohio -- It's been a relatively quiet season for West Nile virus, but state officials said Ohioans should not let their guard down.

The virus is spread by mosquitoes and remains a threat each year until the first hard frost.

The Ohio Department of Health said the state has seen 56 human cases of West Nile virus this year, including one death. While that's up from last year's tally of 12 cases and two deaths, it's a far cry from 2001, when the state recorded more than 440 human cases and 31 deaths.

Health department spokesman Kristopher Weiss said the numbers could easily go higher again the next time there's a wet spring followed by a dry summer -- weather that's favorable to mosquito breeding.