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The Sacramento Bee
How common is Lyme disease in California? Tick-borne infections spread across US
By Madeline Everett, Sarah Linn,
2 days ago
This story and visualization are part of our new “Data In Your Life” series, in which we mine public databases to tell quick stories about the world around us.
There were more than 62,000 reported cases of the tick-borne disease in the United States in 2022, according to the U.S. Centers for Disease Control’s data.
However, the true number of cases each year could be seven times that number due to underreporting, the CDC estimates.
The prevalence of the disease, which is spread to people through the bite of a blacklegged tick, or a deer tick, has increased dramatically since the United States first began tracking the disease in 1991.
While better surveillance explains part of the increase, warming climate has also made more of the country suitable for the ticks that carry the disease.
See how deer ticks have spread across the United States since 1996.
Which U.S. states have the most Lyme disease cases?
As ticks have spread across the nation, so has Lyme disease.
In 2022, Vermont had one of the highest numbers of cases per capita with nearly 200 cases per 100,000 people, according to the CDC.
In 1996, Vermont had only one case per 100,000 people.
The Midwest has especially increased in cases, CDC data show.
How common is Lyme disease in California?
Although Lyme disease is most common in the Northeast, mid-Atlantic, and upper Midwest regions of the United States, dozens of cases are reported each year in California, the CDC said.
According to the CDC, the prevalence of the disease in California has steadily decreased since 1991, when a total of 265 cases were reported in the state.
The number of Lyme disease cases in California has dropped sharply in recent years.
There were just 77 cases of Lyme disease in California in 2022, compared to 145 in 2017 and 144 in 2019.
What is Lyme disease?
Lyme disease is a bacterial infection that’s spread to people through the bite of blacklegged ticks, according to the CDC.
“If left untreated, infection can spread to joints, the heart and the nervous system,” the agency said.
Lyme disease is typically reported in the spring, summer and fall, but ticks can be active at any time that the temperature is above freezing.
The most prevalent and commonly known tick-borne disease in North America is Lyme disease. (Dreamstime/TNS) Dreamstime/TNS
What are symptoms of insect-borne disease?
Lyme disease can be identified by a red, circular skin rash that appears at the site of a tick bite three to 30 days after being bitten.
The CDC advises going to a health care provider immediately as soon as this type of rash, known as erythema migrans, is visible.
Other symptoms include: fever, headache and fatigue, and a characteristic skin rash called erythema migrans. If left untreated, infection can spread to joints, the heart, and the nervous system.
When treated early, Lyme disease symptoms can go away entirely. However, if it is not treated early, the disease can be chronic, with symptoms such as arthritis, fatigue and persistent body aches.
As ticks spread, the US is getting smart about reporting infections and seeing the true extent of Lyme disease . The Centers for Disease Control and Prevention — the federal agency that monitors diseases and establishes guidelines to protect human health — published a paper in February that shows cases of Lyme disease jumped nearly 70 percent nationwide in 2022. But what looked like an alarming spike in disease was actually the result of smarter disease surveillance that better reflects what’s happening on the ground. The CDC revised its Lyme reporting requirements in 2022, making it easier for states with high infection rates to report those cases. The report, the first published analysis of the new data collection guidelines, demonstrates the crucial role efficient surveillance plays in better understanding the scope of infectious disease in the U.S. — and what more must be done to safeguard public health as climate change fosters the proliferation of ticks. ”Disease surveillance that is interpretable and is standardized is integral to being able to understand how disease frequency is changing, and if it’s changing,” said Kiersten Kugeler, a CDC epidemiologist and lead author of the paper. She noted that climate change will complicate the already difficult task of monitoring and controlling diseases such as Lyme. Cases in some areas will continue rising, and they’ll decline in others, as parts of the U.S. become more amenable, or hostile, to ticks. “It’s not going to be straightforward,” Kugeler said. “It’s going to be incredibly important to have good surveillance to be able to understand how climate is affecting risk of disease.” Studies have documented significant shifts in Lyme trends across the country. The illness is caused by the bite of a black-legged tick and causes symptoms that range from flu-like and mild to neurological and debilitating, depending on how quickly the disease is diagnosed. Cases doubled in the three decades between 1990 and 2020. Many researchers, including CDC employees, say climate change is one factor behind that precipitous rise. Environmental changes such as urban sprawl and swelling populations of white-tailed deer, among other drivers, also play a role. Warmer winter temperatures have coaxed black-legged ticks into regions that have historically been too harsh for the blood-sucking arachnids. Meanwhile, milder spring and fall seasons have given the pests more time to breed. Lyme is a portent of climate-driven diseases to come. But, as it has spread into new areas and infected more people, the CDC has struggled to capture the full impact. In 2022, the agency redoubled its disease surveillance efforts, with a special emphasis on vector-borne disease. As part of that push, the CDC loosened its Lyme disease reporting requirements in the Northeast, mid-Atlantic, and upper-Midwest, where cases are high. Public health departments in those areas no longer have to track down the clinical details of each positive Lyme test, such as a patient’s symptoms and when they began, and doctors can skip the labor-intensive process of recording and reporting them. Now, a positive laboratory test is sufficient. Eliminating these steps takes the onus off doctors and local public health authorities and puts it on state health departments, which are typically better equipped to handle it. ”We have a lot of behind-the-scenes data management that’s new with this Lyme disease surveillance system,” said Rebecca Osborn, a vector-borne disease epidemiologist at the Wisconsin Department of Health Services. But overall, she said, “It has gotten quite a bit less burdensome.” The new system runs the risk of including information on people who no longer show symptoms but are still testing positive for the bacteria, which can linger in the blood for years after the infection has gone. But those cases likely comprise a small fraction of the overall data, the CDC said. In areas where Lyme remains rare, providers must continue reporting clinical information for each case. These relatively modest changes to the case definition requirements unearthed 62,551 cases of Lyme nationwide. That’s 1.7 times the annual average reported from 2017 to 2019. Still, most cases of Lyme disease in the U.S. go unreported. Studies based on health insurance records estimate that roughly 500,000 cases are diagnosed every year. Those reported by states to the CDC in 2022 comprise less than one-fifth of that. Elizabeth Schiffman, an epidemiologist with the Vector-Borne Diseases Unit at the Minnesota Department of Health, said figuring out how to capture every case is nearly impossible and perhaps beside the point. ”No system is ever perfect,” she said. “We’re always going to miss something, we’re always going to count something that probably shouldn’t be counted.” If the CDC could use the data it collects every year under its new system to measure the overall impact of Lyme, Schiffman said, then the number of cases it already knows about may be enough. ”If what we are able to capture is able to give us an idea of where things are happening, how things are changing, and inform good public health actions, then it could be argued that we don’t need to count every case.” The data deficit and lack of standardization among states becomes more of a problem when researchers try to tease out the impacts of climate change on the disease. The CDC argues that in regions where Lyme incidence is still relatively rare, the updated surveillance system doesn’t make sense. Doctors and local health departments in those areas still need to collect clinical information on every potential Lyme patient, because each case is a revealing datapoint rather than a statistic in a larger trend. But the burdensome requirements in low-incidence areas muddy efforts to detect the role of climate change in how black-legged ticks may be migrating, said Richard Ostfeld, a senior scientist at the Cary Institute of Ecosystem Studies who researches tick-borne illnesses. The prevalence of Lyme disease typically falls along geographic lines. Counties in the upper Midwest and Northeast report tens of thousands of cases each year, while those in the Southeast and South report hundreds. Although the CDC’s revised reporting guidelines more accurately revealed the extent of Lyme disease in areas with a high prevalence, the implementation of the system over time may obscure growth of the disease elsewhere. The new guidelines “would tend to bias your estimate of geographic trends toward more growth in incidence in northern parts of the country as opposed to southern parts of the country where you’re still being very conservative,” Ostfeld said. “It complicates matters for those trying to understand the role of climate change.” North Carolina, for example, a state long classified as low-incidence, was among five states with the highest number of Lyme disease-related insurance claims in 2016, according to one analysis. But the disease reporting there, said Noah Johnston, director of the Lyme awareness group Project Lyme, still isn’t where it needs to be. “There’s an expectation that tick populations in North Carolina are not as high as they are in the Northeast,” he said. The benefits and drawbacks of the CDC’s updated surveillance highlight the difficulties of tracking and controlling infectious diseases under climatic conditions that are rapidly shifting the distribution of disease carriers. Incremental adjustments to the status quo might not be enough to keep up with the growing scale of disease risk. “We’re likely going to see more and more cases of these diseases and more and more diseases that are going to affect not just our population in the U.S., but globally,” said Osborn. “Public health in general needs to become a little more proactive in our responses. We’re still working on that as a field.” Gordon Chibroski // Portland Press Herald via Getty Images
How to prevent tick bites and avoid getting sick
The CDC advises that people wear long pants and shirts when in tick-infested areas, such as wooded areas or areas with tall grass, and to tuck pants into socks to create a barrier.
The agency advises checking sensitive areas such as armpits and behind ears after spending time outside in one of these areas.
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that's why I hate cats, especially strays. they carry ticks and people think the cat's just scratching itself because of fleas 🤣
Mia
2d ago
Lume disease is likely way more common than stated here. The diagnostic criteria from the CDC is severely flawed and leads to many undiagnosed cases. It happened to me. I was lucky that I ended up finding an infectious disease specialist in San Francisco who ordered additional testing which then showed I had Lyme disease, even though according to the cdc it was not a positive diagnosis. My antibodies were going up as was shown on subsequent blood tests - a clear sign I was fighting the disease - but not according to the flawed diagnostic guidelines from the CDC. He prescribed doxycycline for 5 weeks and I was cured - but so many are not and it can lead to severe, lifelong and life changing disability’.
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