While Missoula County is dealing with an outbreak of new cases of HIV, health officials say the situation is a lot different in Gallatin County.

Missoula County officials recently reported that the county saw 12 new documented cases of HIV in the last five months, enough to classify it as an outbreak.

However, in Gallatin County there have been only seven new cases reported in the last five years. There was one new case last year, two in 2010, three in 2009, none in 2008 and one in 2007.

“It’s nothing, thank goodness, at all like what Missoula has seen recently,” said Gallatin City-County Health Director Matt Kelley.

AIDS Outreach, a Bozeman nonprofit that offers services to people living with HIV and AIDS, estimated that about 80 people have reported living with HIV and AIDS in Gallatin County.

According to the Missoulian, all 12 new cases in Missoula involve adult men who contracted the virus through situations ranging from presumed monogamous relationships to anonymous sexual encounters.

A similar outbreak happened in Yellowstone County a year ago. Six new cases were reported in less than a month between March and April.

HIV — human immunodeficiency virus — destroys the body’s ability to fight off sickness. HIV causes AIDS, or acquired immunodeficiency syndrome. The virus spreads through unprotected sexual activity, by using infected needles or through birth or breast milk if the mother is infected.

Montana is considered a “low incidence” state. There are 529 known cases of HIV in the state; however, that number doesn’t include people with HIV who are receiving care from other states or who aren’t in the care of the Montana system. Nor does that statistic include undiagnosed cases.

According to a 2010 report by the Montana Department of Public Health and Human services, almost nine of every 10 reported HIV infections in Montana were in men. The average age of HIV diagnosis is 37, though people aged 25 to 34 have the highest testing rates.

Kelly said the biggest lesson to be taken from the Missoula outbreak is to get tested for HIV. While the virus is found predominantly in men, anyone who is sexually active or uses intravenous drugs can contract it, Kelley said.

“We urge people to get tested,” Kelley said. “I think all adults should get tested at some point in time. It doesn’t matter if you’re gay or straight, or a man or a woman.”

Greg Smith, executive director of Bozeman’s AIDS Outreach, emphasized the need for anyone at risk to be tested.

HIV can sit dormant in a relatively healthy person’s system for up to 10 years before symptoms appear, Smith said. The longer HIV goes untreated, the more damage it does, he said. The virus attacks soft tissues like the brain, eyes and internal organs.

Within a month of taking medication, an HIV-positive person’s viral load can be undetectable, and they will be 96 percent less likely to pass on the virus, he said.

“If we could get all the people who are positive on meds, we could reduce this,” Smith said. “It’s going to take a lot of effort though.”

While Gallatin County hasn’t experienced an outbreak, keeping an eye on what happens across the state is important, Smith said.

“We want to know what’s happening and we want to know what the social behavior of people is to understand how HIV is being spread,” he said.

The Centers for Disease Control estimates that roughly 20 percent of people living with HIV in the United States don’t know they have the virus. That percentage could be even higher in Montana, Smith said. Many people who have the virus who get tested have already progressed to AIDS, he said. That means those people may have unknowingly infected others.

“I think it’s shame and guilt that’s not allowing them to be tested,” Smith said. “When something’s primarily passed through sex, unfortunately Montana still has a big sense of shame about any sexual behavior. We can’t talk about it openly.”

Smith suggests that sexually active people get tested every six months or after every three sexual partners.

Whitney Bermes can be reached at wbermes@dailychronicle.com or 582-2648.