- Researchers say Lyme disease appears to be becoming more common.
- They estimate about 14 percent of the world has had Lyme disease with the highest rates in Europe.
- The disease is transmitted through the bites of ticks carrying bacteria that causes the illness.
- Symptoms such as muscle aches, fever, headache, chills, and swollen lymph nodes typically appear 3 to 30 days after a tick bite.
About 14 percent of the world’s population may have had Lyme disease at some point.
That’s according to new research published in BMJ Global Health in which scientists reported that Lyme disease is most common in Europe.
They noted that about 9 percent of the population in North America and South America has had Lyme disease.
“(Lyme disease) has continued to spread globally in recent years as a chronic, multisystemic vector-borne disease,” the study authors wrote.
“Such vector-borne diseases, which are characterized by specificity of geographical distribution and frequent emergence and introduction of pathogens, pose a significant and growing public health problem and are major causes of disease and death worldwide,” they added.
The U.S. Centers for Disease Control and Prevention (CDC) estimates that 476,000 people in the United States are diagnosed and treated for Lyme disease each year.
It is the most common vector-borne disease in the United States and is transmitted through the bite of infected ticks.
“Lyme disease risk is higher in certain parts of the country compared to others. For instance, the highest risk for Lyme disease is in the Northeast, mid-Atlantic and north-central regions. If you are outside in environments with exposure to ticks in those regions, you certainly could be at risk,” Dr. Dana Hawkinson, an expert in infectious diseases and medical director of prevention and control at The University of Kansas Health System, told Healthline.
“In other areas, ticks are able to carry and spread other diseases more commonly than Lyme, such as Rocky Mountain spotted fever and ehrlichiosis. That is why preventive tick measures and post-activity tick checks are so important,” Hawkinson added.
Why Lyme disease may be on the rise
Experts say the rates of infection with Lyme disease are increasing and this may be due to a number of factors.
“Lyme disease does seem to be increasing in prevalence, for several reasons,” Hawkinson said. “First, we just have a growing population. We also have more people doing more activities outside, doctors more willing to test for Lyme disease, longer warmer temperatures throughout the year allowing longer tick-borne illness season (typically April-October), and slowly recognized identification of the bacteria in the U.S. regions where it typically had not been identified.”
Dr. Saahir Kahn is an infectious disease specialist with Keck Medicine of USC in Los Angeles. He says environmental factors are likely also playing a role in the expansion of areas with a higher prevalence of Lyme disease.
“Climate change is increasing the size of the regions where the ticks that carry Lyme disease are present,” he told Healthline.
But Kahn argues the BMJ study may have overestimated the true prevalence of Lyme disease.
“While the study did take into account Western blot confirmation of positive cases, the methods didn’t specify whether CDC criteria were used as the basis for determining positive results. Some laboratories use looser criteria for Western blot positivity that are more prone to false positives,” he said.
“Due to the limitations of the meta-analysis approach used, I think the result of the study is an overestimate of Lyme disease seroprevalence,” he concluded.
How Lyme disease is transmitted
Despite this, the CDC notes that areas of the United States in which Lyme disease is common are expanding.
In the mid-Atlantic, north-central and northeastern areas of the United States, Lyme disease is transmitted through the bite of the black-legged (deer) tick, while on the Pacific Coast the disease is spread by the western black-legged tick.
These ticks can attach to the human body anywhere but are typically found in areas where it is hard to see them such as the scalp, groin, or armpit.
In the majority of cases, infection is spread through the bite of an immature tick known as a nymph.
These are difficult to see due to their size of less than 2 mm. Typically, a tick has to be attached to the body for between 36 to 48 hours before the bacteria that causes Lyme disease is transmitted.
Common Lyme disease symptoms
Between 3 and 30 days after a tick bite, a number of symptoms may appear.
These may include aches in the joints and muscles, fever, headache, chills, and swollen lymph nodes.
Between 70 and 80 percent of people with Lyme disease will also get a rash where the tick bite was located, typically 7 days after the bite.
The rash may be warm when touched and if it grows it may take on the appearance of a target or “bull’s-eye.”
Experts say the best way to avoid Lyme disease is by avoiding tick bites in the first place.
“If you are outdoors in an area where ticks that carry Lyme disease are present, you should wear clothing that covers your skin and check your skin and your clothes for ticks after you come home,” Kahn said.
There are also a number of at-home tests that can help determine if you have Lyme disease.
Some advice on treatments
Lyme disease can be treated with a two-week to four-week course of antibiotics.
However, some people will experience symptoms such as fatigue, pain, or cognitive difficulties for more than 6 months after treatment. This is known as Post-Treatment Lyme Disease Syndrome.
Evidence for the use of antibiotics for chronic, persistent symptoms following the initial infection is inconclusive and Khan cautions against this approach to treating long-term issues.
“While many non-specific chronic symptoms are attributed to Lyme disease due to likely false-positive serologic testing, there is no evidence that long-term treatment with antibiotics has any impact on these chronic symptoms, so be wary of any doctor offering cash-only long-term antibiotic treatment for Lyme disease,” Kahn said.
“I see many patients that have paid unscrupulous doctors in cash for these dubious Lyme disease treatments, and in most cases, their symptoms are due to something other than Lyme disease,” he warned.