A Half-Million Americans May Have Tick-Linked Meat Allergy, C.D.C. Says

In total, more than 90,000 people received positive tests over that time period, and the number of people with positive tests increased annually, from about 13,000 in 2017 to nearly 19,000 in 2021. Roughly 20,000 cases had been identified in an earlier study, yielding a total of 110,000 suspected cases from 2010 to 2022.

The rising number of cases identified annually could stem from increasing awareness, an increase in the true prevalence of the syndrome or a combination of both. Lone star ticks are expanding their range, likely as a result of climate change, and other diseases they carry, such as ehrlichiosis, have also become more common in recent years.

Alpha-gal syndrome was most common across a large swath of Southern, Mid-Atlantic and Midwestern states, where the lone star tick is known to live, the researchers found.

But there were also clusters in northern Minnesota and Wisconsin, which are not known to be homes for the ticks. Although some of the people who tested positive may have acquired the disease elsewhere, the results also highlight how much remains unknown about alpha-gal syndrome. “I don’t think that the lone star tick is the full story,” Dr. Jerath said.

In a second study, researchers surveyed 1,500 clinicians, including doctors, nurse practitioners and physician assistants, using an online survey. They found that 42 percent of participants had not heard of alpha-gal syndrome. An additional 35 percent said they were “not too confident” that they could diagnose the illness or manage patients who had it. Of the clinicians who did know about the syndrome, 48 percent said they did not know what test they should order to diagnose it.

Dr. Salzer stressed the importance of tick bite prevention, noting that unlike some other tick-borne diseases, alpha-gal syndrome has no treatment or cure. “Alpha-gal syndrome can be a lifelong condition,” Dr. Salzer said. “It definitely needs to be a part of the conversation of why tick prevention is so important for public health.”