There’s still a slew of questions about why some people develop alpha-gal syndrome.

In some parts of the US, up to 30 percent of people may carry the antibody behind a red meat allergy spurred by tick bites, far exceeding the estimated number of people who actually have the allergy, according a study published in Morbidity and Mortality Weekly Report.

The findings suggest far more Americans than previously thought may be at risk of the allergy, which can make having a hamburger for dinner a potentially life-threatening choice.