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Syphilis cases increased 33% in Minnesota last year, spreading beyond a high-risk group of men who have sex with other men to include more women as well as infants exposed prenatally.

The 1,457 syphilis cases in 2021 included 15 congenital cases in infants, an increase from seven such cases in 2020. The total combined with 22,578 chlamydia cases and 9,671 gonorrhea cases to cause a 1% increase in sexually transmitted diseases last year despite the impact of the COVID-19 pandemic on social and sexual activity levels.

Understanding the precise role of the pandemic will take time, including whether it discouraged sexual encounters or the amount of testing and partner notification efforts that can reduce the spread of STDs, said Christine Jones, the STD section manager for the Minnesota Department of Health, which published the updated data Wednesday.

"What we do know is that the rates of syphilis are troubling," Jones said.

The state also reported an 8% increase in new cases of HIV from 275 in 2019 to 298 in 2021, mostly centered on outbreaks in the Twin Cities and Duluth. The comparison was made with two-year-old HIV data because of irregular testing and diagnosis of HIV in the first year of the pandemic in 2020.

There are now 9,697 people living in Minnesota with HIV infections, including 44% who have AIDS, the disease that is diagnosed when the infection causes substantial damage to the immune system.

There were 27 deaths in 2021 related to underlying HIV infections, which is an increase from 22 in 2019. However, HIV-related deaths have been declining for several years amid improved treatments with drug combinations. People 50 and older make up more than half of the population living with HIV in Minnesota.

Most cases of syphilis have been found in the Twin Cities, primarily among men who have sex with other men, but the growth in Minnesota also has been fueled by an outbreak in Duluth as well as pockets in northwestern Beltrami and Cass counties. Syphilis can be severe if left untreated and can lead to complications including blindness and dementia.

Disparities exist for all STDs, with rates being particularly higher among black and Native American Minnesotans.

The Health Department called the growth in female syphilis cases "alarming," with the number of early-stage infections in women increasing from 163 in 2020 to 253 in 2021. Totals had been lower than 30 every year until 2013.

The rise also increases the risk of prenatal transmission. Congenital syphilis cases were uncommon before 2015 but the state reported 10 in 2018 and then 21 in 2019.

"People need to know they can protect themselves and their infants by consistently using condoms and by getting tested for syphilis and other STDs, and if positive, by getting treatment and informing their sexual partners," said Dr. Ruth Lynfield, state epidemiologist and medical director of the state Health Department.