Geber86 | E+ | Getty Images

There's another kind of STD floating around. It's a nasty financial bug you can pick up from your partner: Sexually transmitted debt. And it may well amount to an epidemic, according to Finder.com. Sexually transmitted debt is where one person in a relationship becomes responsible for their partner's financial debt usually after being convinced or misled into taking on debt in their own name. Finder.com's report, based on a survey conducted in June of more than 2,000 adults, says 74 million Americans have taken on responsibility for debt from a current or ex-partner. It's similar to an STD in that you can catch it from someone you love. Marriage is the top risk factor. Next up: Purchases made in someone's name, purchases made through joint accounts, secret spending by a partner, and divorce settlements. Credit cards top the list, followed by auto loans and student loans. The average amount of debt is estimated at $11,845, for an estimated $250 billion in total acquired debt.

The findings are surprising for two reasons, says Jacquette M. Timmons, a financial behavioralist and author of "Financial Intimacy."First is the staggering amount. "I knew [the numbers] were high," she said, "but $250 billion is a lot of money." The other surprise is what causes relationship-related debt. "I would have expected that after credit cards, student loans would have been the next highest [source of debt]," Timmons said. When she was researching and writing her book, Timmons came across many couples who actively hide debt. It wasn't so much a matter of obscuring their spending habits, but being "completely veiled about the fact they had debt, and how much," she said. This all points to a critical need for people to be completely transparent about their finances in a relationship.

Debt on its own may not be the issue people think it is, Timmons says. "Most couples today are dealing with debt of some sort," she said. Clouding the issue, Timmons says, is that the U.S. now has a huge debt-shaming culture. "We treat people as if there's something wrong with it," Timmons said. "Not all debt should be treated in same fashion." Lifestyle-driven debt is entirely different from student loan or medical debt, or building up a business using credit card debt.