Hello and welcome to Healthbeat's weekly report on stories shaping public health in the United States.

This week, I'm highlighting the news that tick season has begun in the United States, with cases rising three-fold in the past month. We have good news about one of the most feared infections transmitted by ticks, Lyme disease, and not so good news about a non-infectious disease caused by ticks, alpha-gal syndrome.

I am Dr. Jay K. Varma, a physician, epidemiologist, and public health expert currently serving as chief medical officer at Fedcap, a global nonprofit focused on economic mobility and well-being for vulnerable communities. Views expressed here are my own.

Tick season has arrived early and aggressively

The Centers for Disease Control and Prevention reported last week that emergency department visits for tick bites have risen roughly three-fold since March, from 34 per 100,000 visits to 96 per 100,000. That is the highest rate for this point in the year since 2017. The Northeast and Midwest have the highest rates of tick bites, with the Northeast already at nearly 50 tick-bite ER visits per 100,000.

What we call "tick season" in the United States is the stretch from roughly April through September, when warming weather draws ticks out of leaf litter and into the grassy, brushy edges of yards, parks, hiking trails, and gardens. 

Ticks are often present at the tips of grass blades and low shrubs, then grab onto deer, dogs, or humans as they brush past. Tick bites and diseases transmitted by them are rising because of climate change. Warmer temperatures are allowing tick populations to survive further north and to extend their activity for longer periods of the year.

The two ticks of greatest public health concern in the United States right now are the blacklegged tick (also known as the deer tick) and the lone star tick. The blacklegged tick transmits Borrelia burgdorferi, the bacteria that cause Lyme disease, as well as less common infections such as babesiosis and anaplasmosis. 

Another type, the lone star tick, is driving the rapid rise of alpha-gal syndrome, a delayed allergy to red meat. The lone star tick is identifiable by the white spot on the back of adult females and is notable for actively crawling toward people, rather than simply lying in wait to bite. 

Lyme disease is, by far, the most common tick-borne illness in the country, with about 476,000 people diagnosed and treated each year. Alpha-gal is rarer, but causes substantial difficulty for patients and may be increasing. Both conditions are the focus of important news in the past month, so let's take them in turn.

Will we soon have a vaccine for Lyme disease?

A vaccine for Lyme disease is important, because many initial infections are missed. Untreated Lyme can cause arthritis, heart problems, and neurologic complications, and, even when infection is caught early and treated, some patients report long-lasting fatigue and pain. A vaccine could potentially prevent or reduce these conditions.

What’s less well known is that we had a Lyme vaccine in the 1990s. In 1998, the Food and Drug Administration approved LYMErix, a vaccine that was about 76% effective in preventing infection. Although the scientific data for the vaccine was strong, demand for it plummeted after people began reporting arthritis-like symptoms after receiving the vaccine. 

It turns out that the rate of arthritis-like symptoms was similar in the general population and that symptoms did not correlate with the second or third dose, as a true immune-driven side effect should. Nevertheless, a class-action lawsuit was filed, and GlaxoSmithKline pulled the vaccine from the market in 2002. 

Now, more than two decades later, Pfizer and Valneva have announced phase 3 results for a new Lyme vaccine candidate, PF-07307405. The vaccine works through an unusual and elegant mechanism: It generates antibodies in your bloodstream that the tick ingests when it bites you. Those antibodies disable the bacteria inside the tick before they can be transmitted into your body. 

In the VALOR trial, Vaccine Against Lyme for Outdoor Recreationists, the vaccine was 73% effective at preventing confirmed Lyme disease 28 days after a fourth dose and about 75% effective one day after the fourth dose. 

Although these numbers are promising and Pfizer says it will submit for regulatory approval, there are some important concerns:

• First, fewer Lyme cases occurred during the trial than expected, so the primary statistical endpoint was not technically met, even though the secondary analysis was.

• Second, this is a four-dose vaccine (three shots in the first year, then a booster before the next tick season). In my experience as both a physician and leader for large-scale vaccine programs, it is extremely difficult to get adults to complete a four-dose vaccine series.

• Finally, in the current anti-vaccine environment, I worry whether the FDA will consider this vaccine, whether the CDC would promote it even if the FDA approves it, and whether the public will actually accept it. It would be deeply unfortunate if we relived the LYMErix story a second time.

Alpha-gal is rising, but is it more widespread than we realize?

If you have not heard of alpha-gal syndrome yet, it’s likely you will in the near future. It is a delayed allergic reaction to red meat (e.g., beef, pork, lamb, sometimes dairy and gelatin) caused by a sugar molecule called galactose-alpha-1,3-galactose, abbreviated as “alpha-gal.” 

The lone star tick carries this molecule in its saliva. When the tick bites you, it can trigger your immune system to make antibodies against alpha-gal. After that, eating a hamburger may cause hives, vomiting, stomach cramps, or, in some cases, life-threatening anaphylaxis several hours later. It has been called "the midnight allergy," because patients often eat dinner, fall asleep, and wake in the night to a full-body reaction.

The foundation of any public health response to a disease is to count it. You cannot prevent what you cannot see. Yet alpha-gal surveillance in this country is patchwork, as described in a recent article. 

Arkansas became the first state to make alpha-gal a reportable condition in 2023, and more than 15 states track cases to some degree. New York, which is home to one of the country's most concentrated hot spots in Suffolk County, does not track cases statewide. New York City does — and has documented 280 suspected cases since 2024 — even though the lone star tick is not common in the five boroughs. 

The CDC has documented more than 110,000 suspected cases since 2009 and estimates the true number could be three to four times higher. 

Without comprehensive surveillance, public health agencies cannot warn their communities about how common it is and who is likely to get it. Clinicians are less likely to consider it, and patients spend time bouncing between specialists before they are diagnosed. 

Where to look for advice on tick bite prevention

Although changes to its website have been problematic, the CDC does remain an excellent resource for information on how to prevent tick bites.

The single best protection is a combination of applying Environmental Protection Agency-registered repellents on your skin, treating shoes and clothes in permethrin, walking the center of trails, and conducting full-body tick checks within two hours of coming inside.

If you are bitten, consider using the CDC’s Tick Bite Bot that walks you through what to do.

ICYMI

Here’s a recap of the latest reporting from Healthbeat:

• Measles: What South Carolina learned from the largest U.S. measles outbreak in 35 years

• Vaccines: New York City Council passes plan to step up education on vaccines

• Asian needle ant: Researchers warn of threats – to humans and native plants – from little-known ant

• Research: Scientists find clue to cause of noma, an illness that disfigures children across Africa

Until next week,

Jay