A caution sign hangs at the Oregon state health lab in Hillsboro on Friday. The lab has been testing specimens from around the state for the likelihood of H1N1, or swine, flu.

SALEM, Ore. — State health officials say the number of probable cases of H1N1 flu (swine flu) in Oregon has risen to five.

Dr. Mel Kohn, head of the Oregon Public Health Department, said Friday afternoon that the probable cases are in Lane, Multnomah, Wallowa and Polk counties. Two of the cases are in Multnomah County.

On Saturday, Oregon is expected to receive the state's allotment of anti-viral drugs from the federal emergency stockpile.

Oregon Human Services Director Bruce Goldberg said Friday morning that the state will receive about 500,000 doses of the drugs, along with supplies of gloves and masks. He said health officials have no plans to dispatch anti-virals at this point.

The news came as state officials gave KATU on Friday a rare look inside the Oregon State Public Health Lab in Hillsboro to better understand the H1N1 flu testing process.

It all starts with a doctor collecting a mucous sample from a patient who has tested positive for the influenza A virus. That sample is then sent to the state lab for analysis.

Microbiologists process the specimens. After an extensive dilution process, individual samples are compiled into trays and placed into a PCR machine. Simply put, it’s a cooker that heats up the samples for more than two hours and then kicks out the results.

If those results point to the likelihood of H1N1 flu - a subtype of the influenza A virus family - then it’s up to the state epidemiologist to make the official call on whether it is a “probable” case of that flu, based on what’s learned about the patient’s history, where they have been and who they have been in contact with.

The overall process of receiving the sample, testing and analyzing it takes three to four hours.

The lab has received double if not triple the amount of samples that it usually sees at this time of year, when the traditional flu season is winding down.

Oregon’s lab is expected to receive testing materials from the U.S. Centers for Disease Control and Prevention over the weekend that will allow state health officials to say for certain whether any of Oregon’s “probable” cases are indeed H1N1 flu.