Sexually transmitted diseases and HIV infections declined 2% in Minnesota last year, but health officials are uncertain whether that is because of underreporting amid the COVID-19 pandemic, reduced sexual activity or other factors.

STDs involving chlamydia, gonorrhea and syphilis declined 1% from 33,725 in 2019 to 33,252 in 2020, while new HIV infections dropped 18% from 276 in 2019 to 226 in 2020 — despite the discovery of distinct HIV outbreaks in Minneapolis and Duluth over the past three years.

People at risk for STDs and HIV need to seek regular testing and complete treatments for any diagnosed infections — especially considering that antiviral medications can drive HIV to undetectable levels, said Dr. Ruth Lynfield, state epidemiologist. "This is so essential, because people living with HIV who are taking their medications and have an undetectable viral load do not pass HIV through sex."

Minnesota's STD numbers had routinely reached record highs, largely through increases in diagnosed cases of chlamydia — an infection that often results in mild or no symptoms but can lead to infertility in women and other complications.

Chlamydia cases dropped 11% last year to 21,942 — an oddity because the annual number had risen every year since 2009. But then gonorrhea cases increased by 27% in the same year, surpassing 10,000 for the first time in Minnesota.

That kind of divergence in the numbers is "head-scratching," said Jill Farris, director of adolescent sexual health training and education for the University of Minnesota Medical School's Healthy Youth Development Prevention Research Center.

Antibiotic-resistant strains might have fueled growth of gonorrhea, she said. People during the pandemic also might have had an easier time taking the oral antibiotics to treat chlamydia, but not the injections to treat gonorrhea and prevent its spread.

Farris said she suspects fewer people during the pandemic sought testing for chlamydia because it can be asymptomatic, and that infections might have increased.

"Chlamydia probably had the same kind of increase as gonorrhea did," she said, "but we didn't have the same kind of screening during the pandemic to pick it up."

Testing shortages could have led to underreporting — as testing supplies were preserved for the COVID-19 pandemic, said Christine Jones, manager of the STD section for the Minnesota Department of Health, which released the 2020 STD data on Tuesday.

Some clinics preserved tests for people with symptoms, while others tested only initial patients but not their sexual partners. But Jones said it's unclear how much that affected the annual numbers.

"I can't speak to whether it's because people were social distancing or if it's due to the shortage in testing supplies or opportunities," she said.

Less sex also could have played a role. An international analysis in December aggregated the results of seven studies, including three in the U.S., and found a significant reduction in sexual activity early in the pandemic.

Sexual activity levels could have rebounded, though, Farris said. "When you say 'the pandemic,' there is such a difference between those early days and the fear folks had and then people getting used to the new normal."

Teen pregnancy rates had been declining in Minnesota, and provisional U.S. birth data for 2020 suggest that trend probably continued — regardless of STD trends, Farris said.

STD rates in teens are important because the 15-to-19 age group makes up 6.5% of Minnesota's population but 25% of the state's chlamydia cases and 16% of its gonorrhea cases, according to the U's 2021 Minnesota Adolescent Sexual Health Report, which is being released on Wednesday.

The report will highlight one positive in the pandemic — the growth, out of necessity, in online sexual education and counseling that might remain a preferred option for teens.

"Some adolescents are actually more engaged that way," Farris said.

Minnesota reported that testing and outreach helped level off growth in syphilis cases tied to an outbreak last year in Beltrami and Case counties. New syphilis cases in Minnesota overall declined 3% to 1,093 in 2020.

Two HIV outbreaks are ongoing — one in the Twin Cities that dates back to initial cases in 2018 and one identified this year in Duluth that traces to cases in 2019. New HIV infections have primarily been associated with shared needle usage, homelessness, men who have sex with other men and people who exchange sex for money or shelter.

An estimated 9,422 people in Minnesota are living with HIV, some of whom have AIDS — the disease that is diagnosed when the infection depletes the immune system.

Jones said the Health Department is increasing its use of genomic sequencing data from HIV samples, which hospitals and labs have required since 2018 to submit under a federal reporting policy. Genetic signatures from the viral samples can show how recently people were infected and whether they were linked to outbreaks.

"It can see where there [are] relationships between the virus," she said. "It doesn't give you directionality. It's not going to say who infected who, but it can tell you who has been in that same network — individuals who have been exposed to each other."

Jeremy Olson • 612-673-7744