There’s expected to be an increase this summer in ticks that carry Lyme disease. The ailment has a number of symptoms, some more common than others.

Many parts of the United States expect to see an increase in ticks this summer, so renewed calls have gone out for people to be on the lookout for the distinctive, and less distinctive, symptoms of Lyme disease.

The calls are raising questions about the future of Lyme disease diagnosis and prevention as infections become more common.

The increase also makes it more important than ever to be aware of the early symptoms of Lyme disease, doctors say.

Younger ticks can be more difficult to detect.

Thomas Mather, a professor at the University of Rhode Island specializing in tick-borne diseases, warns in particular about ticks still in their nymphal stage.

He said they are poppy seed-sized dots that are more likely to be lower on a person’s body where they may be harder to spot, or affixed in rarely checked places.

But adult ticks spread diseases like Lyme, too, and catching the symptoms of infection can be difficult.

“There’s the characteristic rash that everybody’s on the look for,” said Dr. Amesh Adalja, an infectious disease physician at the Johns Hopkins Center for Health Security.

That bull’s-eye rash — a solid dot with a red circle around it — can develop at a tick-bite site, indicating Lyme disease transmission.

“When people have the rash, the diagnosis is very simple,” Adalja said.

But if there’s no rash or it went unnoticed, then there are other factors to consider.

Lyme disease can bring on a fever as well as arthritis-like pain, according to the Centers for Disease Control and Prevention (CDC). Other symptoms can include headache, chills, fatigue, muscle aches, and swollen lymph nodes.

Facial paralysis even occurs in some people.

In later stages days and even months after a tick bite, people can experience more severe headches as well as neck stiffness. Rashes may also appear on parts of the body away from the tick bite.

There’s even the possibility of dizziness, shortness of breath and, in extreme cases, inflammation of the brain and spinal cord.

Later diagnoses can be tricky — particularly if the patient never noticed the tick bite — because the symptoms might be confused for other fatigue or muscle ache-inducing ailments.

Doctors are sometimes hesitant to prescribe an antibiotic regimen that might have adverse side effects without a firm idea that Lyme is to blame.

“Sometimes, it’s just the rash itself, but sometimes they don’t get it or notice it. In those situations, it’s hard because lots of things can have those symptoms,” Adalja said.

There is also the matter of location.

Ninety-five percent of Lyme disease cases are in 14 states, concentrated along the Atlantic coastline and Great Lakes, according to CDC. Wisconsin and Minnesota are the only states not along the East Coast.

“If you have them in the area, it always has to be in your mind somewhere” when trying to make a diagnosis, Adalja said.

But as Lyme disease risk grows, diagnostic methods will need to improve.

Adalja said the current two-step blood test method recommended by the CDC can give false negatives.

He’d like to see wider use of newer testing methods, such as a “C6 peptide test” that is more sensitive to the presence of Lyme disease, and can detect strains of the Lyme-spreading bacteria from Europe, as well as from the United States.

New tests like these are already available and being used, but they aren’t yet the official recommendations. New guidelines are currently under revision, Adalja said.

Aside from prevention and early detection, the other tactic for battling the increasing spread of Lyme disease would be a vaccine.

There currently are no vaccines for humans available. One introduced in 1998 was withdrawn from the market when it caused adverse reactions in some patients and suffered poor sales.

Others are in development, but experts believe it will be a while before anything is introduced.

Plus, any vaccine will need to go beyond covering just Lyme disease for it to avoid the problems of the old vaccine.

Mather said there’s “a real need for effective vaccines,” but that the same ticks that can transmit Lyme disease can transmit other diseases and viruses as well.

With past vaccines, he said, “People thought they were protected, but, well, you’re not protected against these other germs. It would be irresponsible to have a single vaccine that protects against one germ when [ticks] transmit other germs, too.”

He thinks the future of vaccines against tick-borne diseases will focus on impeding the transmission process rather than mitigating specific diseases.

That could mean something that would equip the body to respond at the tick-bite site and make it an inhospitable site for disease-causing bacteria.

Read more: Lyme disease is more common and dangerous than you think »

An increase in the number of mice in the Northeast this year signals a likely increase in ticks carrying Lyme disease, according to predictions earlier this year.

The ticks live on mice and other animals such as deer.

In addition, factors like milder winters and urban sprawl into wooded areas are increasing people’s potential exposure to infected ticks.

“When we see rodent populations rise, we see an uptick in Lyme disease cases,” said Adalja.

Adalja has seen an increase in Lyme disease cases in recent years, and credits increased testing and people coming into contact with ticks more often as the primary causes.

“We’re picking up a lot more cases than we would have before,” he told Healthline, noting that some emergency rooms test anyone with a fever for Lyme.

Adalja added that “with people moving into areas that were forested areas, you’re going to see more chances to come into contact with ticks.”

Mather is seeing similar trends.

“There’s a lot to be said about the distribution of people and animals. Animals are finding they can live in closer proximity to humans,” he told Healthline.

For example, if white-tailed deer are no longer being hunted in a certain area, they’re able to live closer to people.

That spread, combined with milder winters, are also allowing the spread of ticks like the lone star tick, which can spread ehrlichiosis, and has expanded its range northward in recent decades.

“I feel we’re in a more-ticks-in-more-places world,” Mather said.

Read more: Get the facts on tick removal »