Gov. Jay Nixon announced Wednesday evening that the state has identified one possible case in Platte County north of Kansas City.
"I want the people of Missouri to understand that this is a situation that could potentially get more serious," Nixon said. "It's cause for concern and for vigilance but not for alarm."
Nixon did not provide any identifying information about the person, such as age, gender or how he or she got sick. He did not know if the person had visited Mexico or had contact with pigs.
County-level health officials have been sending suspicious flu samples to the state for testing, and there have been dozens of tests done at the state level, Nixon said.
The sample from Platte County has been overnighted to the Centers for Disease Control and Prevention in Atlanta for confirmation, Nixon said.
Margaret Donnelly, state Health and Senior Services Department director, said it could take 3 to 4 days before the CDC can verify if the individual has H1N1, commonly referred to as the swine flu. She said the strain of flu was identified as being different than the seasonal flu bug.
"If it's new and it's not what were used to, it's probably a good chance (that it's swine flu)," Donnelly said.
The first reported cases of the swine flu arose in Mexico within the past week and a half. The World Health Organization raised its pandemic alert to 5 out of 6 on Wednesday, which means that the organization thinks a global outbreak is imminent.
"It just so happens at the same time we have our first probable case here," Nixon said.
Nixon said the state is not declaring a public emergency.
He said the possibly infected individual will be treated with antiviral medications and has been encouraged to stay home. The person's family and friends will also be tested.
Swine flu, like other flu strains, is passed from person to person. It cannot be passed through eating pork, though some Mexican cases have been linked to close proximity with the animals.
Nixon said H1N1 causes symptoms similar to the normal flu and that everyone feeling flu-like symptoms should be tested and should stay home. He said the state has enough antiviral medicine to take care of all expected cases.
"You can't rule out that there's going to be an expansion of this," Nixon said.
The first batch of medicine will be distributed in Platte County and then to other health offices across the state. Nixon said the CDC is also sending testing kits to Missouri so that it will be easier to identify cases.