Which states have the highest risk for tick-borne diseases?
Lyme disease accounted for 77% of tick-borne disease cases from 2016–2023, followed by anaplasmosis (10%) and spotted fever rickettsiosis (6%).
Reports of tick bites rise every spring and summer, and, with them, reports of Lyme disease infections. Northeastern states have the most Lyme disease cases; New York, Pennsylvania and New Jersey alone accounted for 47.4% of all cases nationwide from 2019 to 2022. And although Lyme disease is the most well-known and most common tick-borne disease, there are others to be aware of.
What is Lyme Disease?
Lyme disease is the most common vector-borne disease in the US — that is, a disease spread via blood-feeding insects like fleas, ticks, and mosquitoes. Symptoms include headache, fatigue, fever, and a skin rash. In most cases, the disease can be treated with antibiotics. It can spread to the heart, joints, and nervous system if left untreated.
How common is Lyme Disease?
Although it’s difficult to know exactly how many people are infected every year, the Centers for Disease Control and Prevention (CDC) estimates that about 476,000 people are diagnosed and treated for Lyme disease annually. The agency based this number on insurance claims from 2010 to 2018 and it may be an overestimate due to people receiving treatment when they weren’t actually infected.
There were 89,468 reported cases in 2023, or about 27 in 100,000 people. That was higher than 2022’s approximate 19 cases in 100,000 people.
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Why are estimates and reported cases so different? This is partly because reporting is not required, and what is reported varies by health department. Many cases are never reported because they're diagnosed and treated without lab testing.
The CDC attributes increasing tick-borne diseases to changes in land use — suburban development has introduced people into areas where ticks are more likely to live. It also notes that changing climate patterns affect where and when people get bit by ticks.
The CDC estimates that 0% to 50% of blacklegged ticks (more details on the species below) carry Lyme disease, depending on a tick’s age and geographic location. Only infected ticks can spread the disease.
What other diseases are spread by tick bites?
Lyme disease accounted for 77% of all reported tick-borne disease cases from 2016 to 2023. Anaplasmosis made up 10% and spotted fever rickettsiosis made up 6%. The remaining 8% included all other tick-borne diseases.
Reported Lyme disease cases increased 43% from 2022 to 2023.
Reported cases of tickborne diseases, 2016–2023
Spotted fever group rickettsioses (SFR)
Spotted fever group rickettsioses (SFR)
A group of diseases all caused by the same bacteria. Rocky Mountain Spotted Fever (RMSF) is the most serious of the spotted fevers and occurs in patients across the US. Symptoms can include headache, fever, nausea and vomiting, stomach pain, muscle pain, and a rash. RMSF does not result in chronic or persistent infections. Some patients who recover from severe RMSF may be left with permanent damage, such as limb and finger amputation, hearing loss and mental disability. RMSF can also be deadly.
Babesiosis
Babesiosis
A disease caused by microscopic parasites that infect red blood cells. Symptoms can include fever, chills, head and body aches, loss of appetite, fatigue, and nausea. Some infected people may not experience symptoms and usually do not need treatment. It is treatable if diagnosed.
Ehrlichiosis
Ehrlichiosis
A group of diseases caused by bacteria. Symptoms can begin one to two weeks after being bit by an infected tick (including the lone star and blacklegged ticks) and can include fever and chills, muscle aches, headaches, nausea and gastrointestinal distress, and a rash. It is treatable with antibiotics.
Anaplasmosis
Anaplasmosis
A disease from bacteria most often due to a blacklegged or western blacklegged tick bite. Early symptoms can include fever and chills, headaches, muscle aches, nausea, vomiting, diarrhea, and loss of appetite. It can be treated with antibiotics. If left untreated, the late-stage illness can progress to respiratory failure, bleeding problems, organ failure, and death.
Tularemia
Tularemia
People can become infected in several ways, including tick and deerfly bites, or contact with an infected animal, such as rodents, rabbits and hares. Common symptoms of tularemia, when transmitted via a tick bite, include swelling of regional lymph glands, sometimes accompanied by an ulcer. This disease is rare and difficult to diagnose, but can be treated with antibiotics.
Powassan disease
Powassan disease
Bites from types of Ixodes ticks, primarily found in the eastern US, are the most common way to be infected with the Powassan virus. Early symptoms can include fever, vomiting, headache, and weakness, and can progress to infection in the brain, or of the membranes around the brain and spinal cord, which can cause seizures, speech difficulty, and confusion. There is no specific treatment other than for symptom relief.
How many people contract tick-borne diseases each year?
Health agencies reported an average of around 55,800 cases of tick-borne diseases per year from 2016 to 2023. The COVID-19 pandemic affected agency reporting in 2020 and 2021, leading to fewer reported cases. The criteria for reporting Lyme disease cases changed in 2022, which may have contributed to an increase in the number of reports that year and beyond.
What states have the most Lyme disease cases?
Northeastern states report more Lyme disease cases than other states. Counties in New York had 19.0% of all cases reported from 2019 to 2022. Pennsylvania followed with 17.1%, and New Jersey reported 11.2% of the total. Sixteen of the twenty counties most affected by Lyme disease are in New York (seven counties), New Jersey (six counties) and Pennsylvania (three counties).
13 of the 20 counties with the highest Lyme disease counts were in New York and New Jersey.
Reported Lyme disease cases by county, 2019–2022
Conversely, Hawaii and Oklahoma reported zero cases from 2019 to 2022, in part due to habitat: blacklegged ticks are not found in Hawaii and a very small percentage of them are infected in Oklahoma.
What other areas are at high-risk areas for tick-borne diseases?
Arkansas had 19.7% of spotted fever rickettsiosis cases between 2019 and 2022, the highest percentage of any state, followed by North Carolina (15.8%), Alabama (10.1%), and Missouri (8.4%). Alaska had zero reported cases.
Five of the 10 counties with the most spotted fever rickettsiosis cases were in Arkansas.
Reported spotted fever rickettsiosis cases by county, 2019–2022
In that same time, New York had the most reported instances of anaplasmosis (30.0% of cases), followed by Massachusetts (10.7%) and Maine (10.6%). Washington, DC, and nine states did not report any cases.
Five of the 10 counties with the most anaplasmosis cases were in New York.
Reported anaplasmosis cases by county, 2019–2022
How many people go to the emergency room for tick bites?
A reported 510 people went to the emergency room for tick bites annually from January 2017 to December 2025.
On average, most tick bite-related ER visits occurred from April to July. May was the peak with an average of 118. The number of visits dropped in August and September, but rose again in October and November.
Tick lifecycle is a reason for multiple seasons for tick bites — adult ticks are most active in the fall and spring while young ticks (nymphs) are most active in warmer weather.
Tick-related emergency department visits are highest April through July.
Emergency department visits for tick bites by month, 2017–2026
Where do ticks live?
Ticks inhabit nearly all of the United States, with varying concentrations depending on the species and location.
Populations of blacklegged ticks and western blacklegged ticks — the two species that can carry the bacteria that cause Lyme disease — are concentrated on the eastern half of the United States and the Pacific Coast. The blacklegged tick is also linked to pathogens that can cause anaplasmosis, hard tick relapsing fever, ehrlichiosis, babesiosis, and Powassan disease. The western blacklegged tick is also linked to pathogens that can cause anaplasmosis, and hard tick relapsing fever.
Blacklegged ticks are most often found in the eastern half of the US.
Blacklegged tick, or Ixodes scapularis, status by county, 2025
Western blacklegged ticks are most often found on the west coast of the US.
Western blacklegged tick, or Ixodes pacificus, status by county, 2025
The CDC also tracks data for five other tick species that do not carry Lyme disease:
- The American dog tick, primarily found east of the Rocky Mountains and in areas of the Pacific Coast.
- The brown dog tick, which is found worldwide.
- The Gulf Coast tick, which is found along the Atlantic coast and the Gulf of Mexico.
- The lone star tick, which is found in the Eastern, Southeastern, and South-Central United States.
- The Rocky Mountain wood tick, which is found in the Rocky Mountain states (eastern Washington, eastern Oregon, parts of northeastern California, Nevada, Idaho, Utah, Montana, Wyoming, and Colorado).
The CDC recommends using protective clothing, vigilance while outdoors, and limiting tick presence in yards to prevent tick bites and prevent ticks on pets. Most tick-borne diseases are treatable, especially if caught early.
Where does this data come from?
Where does this data come from?
Tick borne disease data comes from the National Notifiable Diseases Surveillance System (NNDSS), a data reporting system managed by the CDC. NNDSS receives and shares case data from state, local, and territorial health departments to help public health monitor, control, and prevent serious diseases.
Lyme disease has been a nationally notifiable disease since 1991. The CDC outlines the following limitations of the data:
- Underreporting and misclassification are common because not all cases are reported and others that are reported are sometimes due to other causes.
- Data is captured by an infected person’s residence, not by the location of where they were infected.
- The timing of data reporting for a given year, might close at a different time than the CDC. As a results state numbers and national numbers for that state might differ.
- The definition of Lyme disease was modified in 1996, 2008, 2011, 2017, and again in 2022. Therefore, comparisons over time should use caution.
Tick surveillance data comes from the CDC’s National Center for Emerging and Zoonotic Infectious Diseases (NCEZID). A zoonotic disease is a disease that can spread between animals and people, like Lyme disease, Salmonella, and rabies.
Data about emergency room visits for tick bites comes from the CDC’s National Syndromic Surveillance Program (NSSP). NSSP data is near real time because it is available as soon as 24-hours after a patient’s visit to an emergency room. All identifiable patient information is removed before their case information is entered into the system. The intent of the data source is to provide public health officials with information to respond to health threats with speed and efficiency.
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