A 28-year-old woman is believed to be the first Utahn known to carry a mutated version of the H1N1 virus. While health officials have not yet identified the woman, or the type of mutation she was carrying, they say the mutated virus more easily attacks the lungs, which often leads to death.

At this point officials are not overly concerned that the virus is spreading from person to person. They say they have no evidence that it can be easily transmitted.

Dr. Rachel Herlihy, deputy state epidemiologist, told the Deseret News that the Centers for Disease Control and Prevention notified her office earlier this week about the Utah case. The state routinely sends isolated H1N1 virus samples to the CDC for further testing, she said.

"This patient is not (a) new case. … We know it was likely a couple of months ago," she said. "We're looking through our records. At this point, we have more than 800 cases to sift through" of people who have been either hospitalized and/or died after contracting the virus.

Herlihy said she doesn't know at this point whether the woman died, or specifically when she contracted the virus.

As for the type of mutation, "there's been some confusion about whether it's 225 or 222. We're not positive on which one the patient had," she said.

Those mutations involve an amino acid change in the haemagglutinin HA1 gene, where the virus attaches to human cells. The change "allows the virus to attach to the lower respiratory tract cells better than it might otherwise do," she said, "allowing the virus to move lower in the lungs than it may normally do."

"While there has been some preliminary association with the lower respiratory tract illness and the mutation, we don't understand the cause and effect" at this point, Herlihy said.

Researchers at the CDC believe that patients who already have the virus deep in their lungs "develop these mutations that allow it to adapt to the lower respiratory tract and attack the lower part of the lung," she said.

"The CDC believes it's the virus adapting to its environment, rather than actually causing a different type of (lower lung) infection," though that has not been confirmed.

What researchers do know about the Utah case is that it is not the Tamiflu-resistant variety, she said.

If the mutated virus from the Utah patient was transmitted to another person that had been vaccinated, "they would be protected," she said, meaning the mutation "is not significant enough for (a vaccinated person) to get the virus if they were exposed to it," but it is not known whether it could be passed to someone who had not received the vaccine.

Herlihy said her office is trying to identify the woman, but once they do "there's really not a whole lot else to do because we don't think it's clinically significant, even if it was transmitted."

The same type of mutation seen in the Utah case "has been happening sporadically since the beginning of the pandemic," she said. "The bottom line is, it's not a big deal. … We don't think the virus had any impact on patient's clinical course."

It would be more significant if a "resistance mutation" had been identified, meaning the virus is resistant to anti-viral drugs like Tamiflu, she said. "But this one is definitely being overblown."

Herlihy said she's "not certain" whether there are any resistance mutations among the viruses being contracted by Utahns. "At this point, that's happened 26 times in the U.S. that have been identified. There is little or no evidence that there has been person-to-person transmission of those viruses."

The Tamiflu-resistant mutations, dubbed "low reactor" viruses, have been documented most recently in eight hospital patients in Wales, and another four at a hospital in North Carolina.

Those resistant viruses have what is known as the H275Y mutation, indicating resistance to Tamiflu, but susceptibility to the second antiviral drug, Relenza.

A global alert issued by the World Health Organization on Dec. 2 said that, "within the past two weeks, the number of documented cases of oseltamivir (Tamiflu) resistance in H1N1 viruses has risen from 57 to 96. Around one third of these cases occurred in patients whose immune systems were severely suppressed by haematological malignancy, aggressive chemotherapy for cancer, or post-transplant treatment."

The news comes as several health departments statewide have started offering the H1N1 vaccine to anyone who has not yet had access to it.

Spread of the H1N1 virus has decreased for the sixth consecutive week in Utah, though it is still above the epidemic threshold.

A weekly report released Wednesday by the Utah Department of Health shows two more Utahns died and 34 others were hospitalized between Nov. 20 and Dec. 5 after contracting the virus.

Deaths reported are a male, age 24-59 in the Salt Lake Valley Health District and a female, age 25-49, in the Weber-Morgan Health District.

Officials said the rate of "influenza-like-illness" in Utah is at 1.7 percent, down from 2.6 percent last week, but still above the "outbreak threshold" of 1.1 percent.

To date, the state has received just over 700,000 doses of the H1N1 vaccine, and new shipments continue to arrive weekly.

e-mail: carrie@desnews.com