The Rock County Health Department Friday reported a probable case of swine flu in an adult male who traveled recently to Mexico.

The man, whose symptoms were mild, isolated himself at home, has no school-aged children and appears to have posed little risk to others, county health officials said at a news conference.

Wisconsin now has 14 probable cases of swine flu -- six in Milwaukee County, four in Waukesha County, and one each in Adams, Ozaukee, Rock and Sheboygan counties -- according to the state Department of Health Services.

Meanwhile, Gov. Jim Doyle has declared a health emergency. The state lab ramped up testing, and experts said the danger lies in the potential of the virus to kill more than regular flu does.

In Waukesha County, three schools have been closed for at least a week. Julianne Klimetz of the county's Department of Public Health said Friday that all three cases are mild, and none of the patients had been hospitalized.

Two other cases were reported Thursday in young adults from Ozaukee County and Sheboygan County, north of Milwaukee, said Dr. Seth Foldy, state health officer. Three probable cases were reported Wednesday — two in Milwaukee and one in Adams County.

Foldy said health authorities were making sure they were not exposing others and were interviewing those who have been in contact with them.

The 40-year-old Adams County man has been isolated and appears to be recovering, said Sue Kunferman, director of the Wood County Health Department.

Dr. Dennis Maki, an infectious disease specialist at UW Health, said the system’s clinics have had two suspected cases of swine flu for which test results are pending.

Nationally, 11 states have reported 109 confirmed cases, including one death of a child in Texas. The outbreak, which erupted last week, continued to be most severe in Mexico.

Wisconsin’s emergency declaration allows the state Department of Health Services to distribute stockpiles of antiviral drugs where needed and the Wisconsin National Guard to help respond if requested, Doyle said.

The stockpile, which is enough to cover about 10 percent of the population, will be used to replenish the supplies of hospitals and clinics that prescribe them to ill patients. The drugs will be made available regardless of whether patients have insurance.

Staff at the Wisconsin State Laboratory of Hygiene, on the UW-Madison campus, have been working extra hours to test specimens for swine flu, said Pete Shult, the lab’s director of communicable diseases.

The lab, which has received more than 228 nasal or throat swabs, is staying open until 11 p.m. each day and will continue testing over the weekend, Shult said.

Specimens that are positive for flu but negative for regular flu subtypes are considered probable cases of swine flu, Shult said, and sent to the Centers for Disease Control and Prevention in Atlanta. If CDC tests indicate swine flu, the cases are confirmed.

The CDC tests will be available in Wisconsin and other states soon, said Dr. Richard Besser, acting CDC director.

The last time the state lab was this busy was 2003, during the Wisconsin-based outbreak of monkeypox, Shult said.

"I would expect our specimen load to continue to climb," he said.

Though swine flu has killed about 168 people in Mexico, its toll has been relatively mild compared to the regular flu, which the CDC says causes about 36,000 deaths and 200,000 hospitalizations in the United States each winter.

Why has swine flu generated so much more attention? Because of its potential to cause much greater harm, said Maki and UW-Madison flu expert Christopher Olsen.

They said five factors set swine flu apart:

• It’s a new virus that differs genetically from regular flu viruses more than previous new viruses have.

• There is no vaccine for swine flu, and the immunity many people have to regular flu viruses from prior infections appears to offer no protection against swine flu.

• The death rate appears to be high, at least in Mexico, though data are preliminary.

• Some of the early victims are reported to have been young and healthy. Most Americans killed by regular flu are elderly, with weak immune systems.

• Unlike the bird flu virus that generated great concern a few years ago or previous human cases of swine flu, this flu appears to spread easily from person to person, like the regular flu does.

"With this virus, the majority of the population is susceptible," Olsen said.

Swine flu could cause a flu pandemic like one that killed up to 50 million people worldwide in 1918, Maki said.

But, he noted, several things have changed since then that could lead to a different outcome.

Medical technology has greatly improved. Antiviral drugs, such as Tamiflu and Relenza, can reduce the severity of the flu. A vaccine might be ready by this fall, when swine flu could swell during the onset of the regular flu season.

Perhaps most importantly, doctors, hospitals, clinics, schools, businesses and other groups have been planning for a pandemic for several years.

"Never before have we had better preparation for an influenza pandemic than we have now," Maki said.

—State Journal reporter Jason Stein and Ryan J. Foley of The Associated Press contributed to this story.