Two North Dakotans have fallen ill with what state health officials believe is the West Nile virus. The cases represent the state's first human outbreak of a mosquito-borne illness that has sickened more than 300 horses in the state.

Neither of the victims is seriously ill, and health officials and Gov. John Hoeven said there was no cause for public alarm. It is rare for a person to show symptoms of the virus, and rarer still for an individual to need medical care, said Dr. Craig Lambrecht, the Health Department's medical officer.

"We do have two cases of West Nile, but these people are doing fine," Lambrecht said at a Wednesday night news conference. "Now, with the cooler weather, hopefully the mosquito activity has curtailed dramatically, so the risk is even less."

One 74-year-old woman, who lives in the Garrison area, is being treated at a Bismarck hospital for the disease, Lambrecht said.

About five days ago, the woman had a temperature of more than 104 degrees, but she is recovering, Lambrecht said Wednesday. He said the woman was never critically ill. She is expected to stay in hospital for about another three days.

The woman became sick abruptly, and went directly to the emergency room, Lambrecht said. She had other health problems, including diarrhea, the doctor said.

"She's doing well. She's sitting up, eating, laughing, smiling," Lambrecht said.

The second case, diagnosed in a 39-year-old Jamestown man, was discovered when the man visited a clinic after suffering a fever, headache and muscle aches for more than two weeks. The man was never hospitalized, Lambrecht said.

"That individual is home, he's continuing to work, he's doing well, and quite frankly the (doctor) was surprised that indeed, the test came back positive," the medical officer said.

West Nile is a virus that can cause headaches, fever and, on rare occasions, serious illness or death. It is carried by mosquitoes, and normally strikes horses and birds. It is not contagious.

"This isn't the flu, this isn't the cold. There is no way that we can pass this from one individual to another," Lambrecht said.

The federal Centers for Disease Control and Prevention says at least 480 human cases of West Nile virus have been diagnosed nationwide, resulting in at least 24 deaths.

Larry Schuler, the state veterinarian, said North Dakota had 320 confirmed cases of the virus in horses on Wednesday night.

Of those, Stutsman County has reported 25 confirmed horse cases, and McLean County, where Garrison is located, has reported three, Schuler said.

North Dakota's state lab first identified the West Nile virus in the two individuals. Final confirmation is awaiting a second analysis at a federal lab in Colorado. Lambrecht said that would take about a week.