What is alpha-gal syndrome?

Alpha-gal syndrome was formally identified in the 2000s and gets its name from galactose-alpha-1, 3-galactose, a sugar that's present in beef, pork, lamb, and the meat of most mammals. Lone star ticks can transmit the sugar to people through a bite, which can lead some people's immune systems to label the sugar as a threat and overreact to its presence when they eat meat.

Symptoms of alpha-gal syndrome often take hours to appear and are wide-ranging, including hives, nausea, diarrhea, and anaphylactic shock, Anthes reports. Even if a patient has the syndrome, they may not feel sick every time they eat meat.

In order to diagnose the condition, clinicians can order a blood test that will determine whether a patient has antibodies against alpha-gal.

Study details

According to two new CDC studies, as many as 450,000 Americans may have the disease, with many of those people going undiagnosed.

For one of the studies, researchers looked at the results of antibody tests performed between 2017 and 2022 and found that more than 90,000 people received positive tests. In addition, the number of people with positive tests increased each year from around 13,000 in 2017 to almost 19,000 in 2021. In total, the researchers identified 110,000 suspected cases from 2010 to 2022.

However, researchers also found that the number of suspected cases is likely a significant undercount. In the second study, researchers surveyed 1,500 clinicians, including doctors, nurse practitioners, and physician assistants, and found that 42% had never heard of alpha-gal syndrome. An additional 35% said they were "not too confident" they could diagnose the disease or manage a patient with it.

Of the respondents who did know about alpha-gal syndrome, 48% said they didn't know what test they should order to diagnose it.

"Our 110,000 suspected cases of alpha-gal syndrome represent those that found the health care provider that did properly send off for the antibody test," said Johanna Salzer, a disease ecologist and veterinarian at CDC, and an author of both studies.

When researchers factored in the knowledge gap, they estimated the true number of people with alpha-gal syndrome may be closer to 500,000, though Salzer noted the figure was a "crude estimate."

Discussion

It's possible the rising number of alpha-gal syndrome cases could come from increasing awareness, an increase in the prevalence of the condition, or both, Anthes reports. Lone star ticks have been expanding their range, and other diseases they carry, like ehrlichiosis, have also become more common.

The researchers found alpha-gal syndrome was most common throughout the Southern, Mid-Atlantic, and Midwestern states — where the lone star tick is known to live — but they also found clusters of the disease in northern Minnesota and Wisconsin, areas not known to be home to the ticks.

While it's possible some people acquired the disease elsewhere, the results highlight some of the unknowns about alpha-gal syndrome, Anthes reports. "I don't think that the lone star tick is the full story," said Maya Jerath, an allergist and immunologist at the Washington University in St. Louis, who has treated hundreds of patients with alpha-gal syndrome.

Jerath added it's clear the condition is significantly underdiagnosed. "This is a story that every patient of mine tells me, that 'I had to go to five physicians before they could tell me what it was,'" she said. "It's nice to have numbers behind it, and it's definitely a call to action."

Salzer stressed how important tick bite prevention is, and noted that unlike some other tickborne illnesses, alpha-gal syndrome does not have a treatment or cure. "Alpha-gal syndrome can be a lifelong condition," she said. "It definitely needs to be a part of the conversation of why tick prevention is so important for public health." (Anthes, New York Times, 7/27)

Over time, climate change has caused several disease-carrying species to become more widespread in the United States, significantly increasing the risk of certain diseases, such as West Nile virus and Lyme disease. However, experts say the United States isn't prepared for future outbreaks, Sara Van Note writes for STAT.