Brace yourself for this daunting piece of dental health news. Cavities can be contagious.

As Anahad O’Connor reports in this week’s “Really?” column, cavity-causing bacteria can be passed from one person to the next.

One of the most common is Streptococcus mutans. Infants and children are particularly vulnerable to it, and studies have shown that most pick it up from their caregivers — for example, when a mother tastes a child’s food to make sure it’s not too hot, said Dr. Margaret Mitchell, a cosmetic dentist in Chicago.

A number of studies have also shown that transmission can occur between couples, too. Dr. Mitchell has seen it in her own practice.

“In one instance, a patient in her 40s who had never had a cavity suddenly developed two cavities and was starting to get some gum disease,” she said. She learned the woman had started dating a man who hadn’t been to a dentist in 18 years and had gum disease.

Read the full report, “The Claim: Dental Cavities Can Be Contagious,” and then please join the discussion below.