New HIV infections rose by nearly 8 percent in Minnesota last year, in what Health Commissioner Dr. Edward Ehlinger called an ongoing epidemic.

While 83 percent of the new cases occurred in the Twin Cities area, increases were reported in all parts of the state except the suburbs, the Minnesota Department of Health said in its annual update on HIV.

The number of new HIV infections rose to 315 last year; up from 292 in 2011, but not out of line with annual counts for the previous decade.

HIV cases among women dropped 19 percent between 2011 and 2012.

Among men, male-to-male sex was the main risk factor, but there was also a sharp increase in cases among people using injectable drugs.

A new case of HIV is reported every 30 hours in Minnesota, said Kris Ehresmann, director of infectious-disease epidemiology at the Health Department.

Condom use and abstinence are effective prevention methods, Ehresmann said. For those who test positive, "treatment is prevention" that can halt the infection's spread, reducing the chances of transmitting the disease to a sex partner.

State health officials also expressed concern that spikes in gonorrhea and chlamydia last year could increase HIV infection rates. Chlamydia saw a 7 percent rise in 2012, according to a recent report, while gonorrhea jumped 35 percent.

"Some of these [sexually transmitted diseases] can increase HIV transmission or the likelihood of getting infected," Ehlinger said.

HIV infection rates among minorities are disproportionate compared with Minnesota's general population. African-Americans made up 24 percent of new infections, the report said, while Hispanics represented 12 percent. People originally from Africa were 13 percent of new cases and had the highest infection rate.

Since the state began tracking the virus in 1982, a total of 10,112 cases of HIV/AIDS have been reported. The state estimates that there are 7,516 people living with HIV, 47 percent of whom have developed AIDS.

Jeff Hargarten is a University of Minnesota student reporter on assignment for the Star Tribune.