JEFFERSON CITY, Mo. — The global outbreak of swine flu apparently has penetrated Missouri, possibly as close as 30 miles south of St. Joseph.

State health lab officials discovered Missouri’s first probable case in a specimen from a Platte County resident, Gov. Jay Nixon announced Wednesday evening. He declined to divulge where in Platte County, the resident’s age or how he or she contracted the virus because the patient hadn’t yet been notified.

The single infection prompted a series of events. The Department of Health and Senior Services has sent the suspected specimen to the U.S. Centers for Disease Control and Prevention for confirmation. The state has asked the Platte County resident to stay at home for at least seven days to prevent the spread of the virus. Family members and those who may have been in contact with the infected person are being tested for the virus as well.

“We are working around the clock to manage, track and detain this virus,” Mr. Nixon said. “While this is cause for concern, it is not cause for alarm.”

The department began Wednesday afternoon distributing its stockpile of anti-viral drugs throughout the state, starting with Platte County.

Swine flu has been known as a respiratory disease in pigs since the 1930s, but recent infections in humans have occurred.

As of Wednesday, the CDC reported 93 cases of swine flu in the United States, with one death in Texas. More than 160 are believed to have died from the virus in Mexico.

The World Health Organization upped its pandemic alert from 4 to 5, calling on all countries to prepare for an outbreak. The highest level is 6.

Besides the United States and Mexico, seven other countries to date have reported swine flu infections. “This is a very fast-evolving situation,” said Sarah Patrick, state epidemiologist.

Platte County not only borders Kansas, which has reported two confirmed cases of swine flu, but also is home to the Kansas City International Airport.

Mr. Nixon said he didn’t know whether the infected Missourian had traveled to Mexico. He said he or she exhibited flu-like symptoms and sought care from a physician, who ran the initial test before sending the specimen to the state. CDC confirmation is expected within four days.

Based on trends in other afflicted states, “You can’t rule out there’s going to be expansion of this,” he said.

Health and Senior Services Director Margaret Donnelly warned that symptoms of swine flu are similar to seasonal influenza in humans and that while infection can spread from pig to humans, it also is transmitted with human-to-human contact.

“We know that the number of this strain of flu is increasing, so to find that we have a case in Missouri is not (any) surprise,” Ms. Donnelly said.

Rep. Jason Brown, a Platte City Republican, asked residents of Platte County to act responsibly and to seek medical assistance as soon as possible if they feel ill.

“Obviously it’s a serious situation, but I don’t think there needs to be any panic,” Mr. Brown said.

Alyson E. Raletz can be reached at alysonraletz@npgco.com.