DENVER -- It is possible swine flu may have already spread to Colorado.

The tests of a suspected swine flu case at Sky Ridge Medical Center have been sent to the Centers for Disease Control and Prevention for analysis, said hospital spokeswoman Linda Watson.

The spokeswoman for the Lone Tree hospital would not elaborate on the age and gender of the person with suspected swine flu, or where they live, but said the patient was swabbed Monday and the tests were sent to the CDC shortly thereafter. Results are expected on Tuesday.

The swabs of several other suspected swine flu cases have been sent to the CDC but the state health department did not say what hospital or what region of Colorado the cases came from. The results should be known in 12-24 hours.

A spokeswoman for Parker Adventist Hospital said she cannot say how many cases they have sent to the CDC for testing.

The state department of health said the test results for two earlier suspected cases have already come back negative.

Earlier in the day, state health officials said it could be just be a matter of time before swine flu cases are confirmed in the state.

"I have to admit I fully expect to identify cases in the near future, given the presence of the virus in other states. We should proceed with our planning accordingly," said Dr. Ned Calonge, chief medical officer for the Colorado Department of Public Health, during an afternoon news conference.

That plan includes monitoring people for flu-like illnesses and respiratory illnesses at hospitals and to stock up on supplies in the case of a pandemic.

"We will be receiving 25 percent of Colorado's allotment of the strategic national stockpile, which will include masks, gloves and other protective equipment as well as other antiviral medications," Calonge said. "This is to pre-position these supplies. We are not planning distribution at this time. Currently there appears to be no commercial shortage of antiviral medication in the state so we anticipate we will have adequate supplies between the national stockpile and the personal healthcare system."

Calonge said the best way to prevent the spread of the swine flu is to reduce one's risk by washing hands and taking other personal precautions. Residents should also have a "shelter in place" plan with enough supplies such as food and water for a few days, he said.

The state is asking individuals with mild flu-like symptoms to stay at home -- regardless of travel history.

"Children and adolescents with fever should not go to school or day care. Adults with fever should not go to work until their symptoms resolve," Calonge said. "Those with respiratory complications or medical indications that could be worsened by the flu should contact their health care provider."

More than 1,600 cases of swine flu have been reported in Mexico, and the suspected death toll is nearly 150. There are 40 confirmed cases in the United States with cases in New York, California, Ohio, Kansas and Texas. Two other states have potential cases under investigation. Worldwide there were 73 cases, including six in Canada, one in Spain and two in Scotland.

The World Health Organization raised its global alert level on the spreading swine flu from a Phase 3 to a Phase 4, meaning there is sustained human-to-human transmission of the virus causing outbreaks in at least one country.

"This does not change our current response or our current plans," Calonge said. "Our response, according to CDC guidelines, needs to be based on local activity and needs to be mirror the severity of the illness."

How Fast Can Flu Spread?

While the swine flu has much of the world on alert, local health experts said the effort is more an attempt to get the word out than a warning of a worldwide pandemic.

"It's too early to say if this is going to be a big problem," said Dr. Ted Eickhoff from the University of Colorado Denver School of Medicine. "There's no reason to sound the alarm, yet."

For one thing, Eickhoff said, it takes about a week to confirm the spread of influenza from one person to another. That delay factor can sometimes mean several cases are reported at the same time.

"You can't extrapolate from what we know now and automatically keep doubling the number of confirmed cases," Eickhoff said.

"Going from 20 confirmed cases in the U.S. Sunday to 40 today could imply this disease has the potential to double every day," said Dr. Randall Kuhn, director of the Global Health Affairs Program at the University of Denver. "Twenty to 400 would be scarier."

He credits U.S. government officials for notifying the public now in order to help limit the spread.

"But even when it spreads it can be isolated in each new country through awareness, healthy habits, and better tracking. It's a unique virus everyone should be paying attention. It seems like it has a high probability of containment," Kuhn said.

Kuhn likened the current situation to the concerns worldwide with SARS, severe acute respiratory syndrome, stemming from high concentrations in China earlier in the decade. In the end, Kuhn said, SARS did not spread quickly enough to become a major, worldwide threat.