The Growing Threat of Lyme Disease in Spring and Summer
As the weather warms up during spring and summer, more people are spending time outdoors. While this is a great opportunity to enjoy nature, it also increases the risk of encountering ticks that can carry dangerous pathogens. The 2026 tick season has already seen a significant rise in activity, with alarming reports from health authorities.
The Centers for Disease Control and Prevention (CDC) recently warned that emergency department visits due to tick bites have reached their highest level since 2017. This trend may indicate an especially severe season ahead for Lyme disease and other tick-borne illnesses. According to data updated on April 12, the rate of tick-related emergency department visits has risen to 71 per 100,000 people, which is more than double the average of about 30 per 100,000 for this time of year.
The Northeast region has the highest rate of tick-related emergency department visits at 163 per 100,000 people, up from just 52 in March. This figure already surpasses recent full-year highs in the region, which ranged from 74 to 89 per 100,000 between 2021 and 2025.
State health departments reported over 89,000 cases of Lyme disease in 2023, the last year for which data is available. However, public health experts estimate that close to 500,000 people in the United States get Lyme disease every year. The disease can be challenging to detect because many people do not notice tick bites and may overlook early symptoms of infection. If left untreated, the infection can lead to serious and even permanent health issues.
What Causes Lyme Disease?
Lyme disease, named after the Connecticut town where it was first identified in 1975, is caused by a group of bacteria called Borrelia, most commonly Borrelia burgdorferi. These bacteria are transmitted by deer ticks, also known as black-legged ticks, which belong to the Ixodes family. Ticks become infected after feeding on animals such as birds, mice, or deer. When they bite a person, they can transfer the bacteria into the bloodstream.
Usually, the tick must remain attached for 24 to 48 hours to transmit the bacteria that cause Lyme disease.
Where and When Does Lyme Disease Occur?
Lyme disease can occur in most regions where deer ticks live. These ticks are most active during late spring, summer, and fall, typically from April to November in most areas. They emerge when temperatures are above freezing. In years with shorter winters, ticks may appear earlier and remain active year-round in regions where freezing temperatures are rare.
Approximately 90% of U.S. cases are reported from states in the Northeast, mid-Atlantic (from Virginia to eastern Canada), and Upper Midwest regions, including Wisconsin, Michigan, and Minnesota. A few cases occasionally occur in California, Oregon, and Washington.
Since 1995, the incidence of Lyme disease in the U.S. has almost doubled. Warmer weather and changes in rainfall patterns have allowed ticks to survive in new parts of the country and for longer periods. Even in regions where ticks have existed before, Lyme disease has become more common due to increased deer populations.
As woodland areas are developed, the habitats of deer and mice may come closer to human settlements, increasing the risk of transmission.
Symptoms to Watch For
Early symptoms of Lyme disease, such as fever, muscle aches, and fatigue, usually appear within three to 30 days after a tick bite. Another classic symptom is a target or bull’s eye rash at the site of the tick bite, which occurs in about 70% to 80% of cases.
Other rashes following a tick bite can also occur, but some may be due to irritation from the bite rather than an infection. If you know you’ve had a tick bite and experience flu-like symptoms or see a bull’s-eye rash, it’s important to consult your healthcare provider about whether you should be treated with antibiotics.
A blood test for antibodies can help confirm the infection, but it can sometimes give a false negative result, particularly in the first couple of weeks of the disease.
In most people, the rash goes away on its own. However, treatment may shorten its duration and is crucial for preventing other symptoms. A two- to four-week course of antibiotics can generally treat Lyme disease. Severe cases might require intravenous antibiotics.
A promising new vaccine for Lyme disease is currently being tested. In March 2026, Pfizer, the pharmaceutical company developing it, announced that in a late-stage study, the vaccine prevented the disease in 70% of people who received it.
Later Symptoms and Long-Term Effects
If left untreated, the bacteria that cause Lyme disease can spread, potentially leading to long-term symptoms. About 60% of people who get Lyme disease and don’t receive treatment can develop arthritis. In rare cases, Lyme disease can also affect the heart and nervous system.
Inflammation in the brain or surrounding tissues can cause headaches, neck pain, balance issues, and memory or behavior changes. It can also lead to nerve damage, resulting in numbness, tingling, and muscle weakness.
These symptoms can appear immediately or much later—sometimes months or even years after infection. In cases where the disease wasn’t promptly treated, late-stage symptoms can persist even after antibiotics kill the bacteria.
Scientists don’t fully understand why this happens, but one study found that some particles from the bacteria’s cell wall may leak into the joints and persist after treatment, causing ongoing inflammation and arthritis symptoms. Another reason for Lyme’s long-term effects is that it can trigger autoimmune disease, where the immune system attacks its own cells.
Because the nervous system may be particularly sensitive to damage caused by the bacteria and related inflammation, healing can take a long time. In some situations, the damage could be permanent.
Preventing Lyme Disease
Until a vaccine becomes available, there are steps you and your family can take to protect against Lyme disease:
- Use tick and insect repellents such as DEET and picaridin, which can be applied to skin, and permethrin, which is sprayed onto clothing, to keep ticks at bay.
- Treating clothing with permethrin may be especially beneficial, as the substance withstands several washes.
- Wear long-sleeve shirts and pants while gardening, hiking, or walking through grass or woods to prevent tick bites.
- Wearing light-colored clothes makes ticks more visible, and tucking your pants into your socks can also prevent ticks from traveling from your pants, shoes, and socks onto your legs.
- Remove outdoor clothes immediately after being outside.
- Washing and drying clothes at high temperature can help kill any ticks on the fabrics, and a quick shower immediately after spending time outdoors can wash ticks off the skin before they attach.
- Perform daily tick checks, paying special attention to warm areas like your armpits, neck, ears, and underwear line. If you find a tick attached, use tweezers to pull it off, holding them perpendicular to the skin.
- If you find a tick that may have been on the skin for more than 36 hours, ask your healthcare provider if a dose of preventive antibiotics would be appropriate, generally given within 72 hours of the bite.
