Lyme Disease vs. Rocky Mountain Spotted Fever: Understanding the Differences

Medically reviewed on July 13, 2022 by Jordan Stachel, M.S., RDN, CPT. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

Table of contents

• What is Lyme disease?
• What is Rocky Mountain Spotted Fever (RMSF)?
• Comparing Lyme and RMSF
• Fight tick-borne illnesses with help from Everlywell

If you’re an avid outdoorsperson living in the US, avoiding a tick bite is likely part and parcel of your wilderness safety plan.

Ticks can carry bacteria that can infect humans and other animals—including Lyme disease and Rocky Mountain Spotted Fever. [1] And, if you’re experiencing symptoms after a tick bite, quick identification can lead to swift treatment and recovery.

In this guide, we’ll break down everything you need to know about Lyme disease vs. Rocky Mountain Spotted Fever (RMSF). We’ll define both illnesses and compare their symptoms, causes, and treatment options to help you stay vigilant during your next outdoor adventure.

What is Lyme disease?

Lyme disease is a vector-borne illness—a sickness spread by arthropods like ticks, mosquitoes, and fleas—that impacts approximately 30,000 people in the US each year according to CDC reports. [2,3]

There are three stages of Lyme disease: [4]

• Early localized Lyme disease
• Early disseminated Lyme disease
• Late disseminated Lyme disease

Early intervention can eradicate the disease in the first stage, and treatment outcomes improve the earlier patients, and healthcare providers can correctly identify the illness.

Depending on how far a Lyme infection has progressed, it can take just a few weeks or multiple years to completely eradicate the bacteria from the body—so, adequate prevention is key. If left untreated, long-term effects of Lyme disease could also arise. If you spend significant time outdoors, you can prevent tick bites by: [5]

• Using EPA-registered insect repellent
• Checking your clothes, shoes, and body immediately after returning home
• Staying up-to-date on local Lyme infections and tick populations

What is Rocky Mountain Spotted Fever (RMSF)?

Like Lyme disease, Rocky Mountain Spotted Fever (RMSF) is a vector-borne illness transmitted via a Rocky Mountain wood tick or brown dog tick carrying infectious bacteria. [6]

This infectious disease is significantly less common than Lyme disease—while the number of confirmed cases rises each year, only around 5,000 infections were reported to the CDC in 2019. [7]

The disease develops in two stages (early and late illness), but symptoms can change rapidly with some late-stage infections setting in only five days after exposure.

RMSF prevention isn’t unlike Lyme prevention, but people who spend ample time outdoors can stay vigilant by:

• Understanding the differences between Lyme disease vs. Rocky Mountain Spotted Fever
• Avoiding wooded, tick infested areas
• Performing routine tick checks after returning from the outdoors

Comparing Lyme and RMSF

Let’s explore some similarities and differences between the two illnesses to help you identify and treat each one.

Symptoms

Lyme and RMSF share a few symptoms, including:

• Fever
• Headaches
• Rashes
• Chills

But, the rashes that present in each illness are distinct:

• A RMSF rash can appear as red pinpricks or splotches covering the skin
• A Lyme disease rash can take a variety of forms, but bullseye lesions are the most common. [8]

RMSF also features a distinct symptom that can help healthcare providers and patients rule out Lyme disease—nausea or vomiting. Lyme infections typically don’t present with gastrointestinal symptoms, so stomach troubles can distinguish an RMSF infection from Lyme.

In addition, a rash typically doesn’t develop in RMSF patients until the second stage. A Lyme disease rash can occur within days after being bitten by an infected tick.

Causes

Both illnesses are spread by ticks, but different bacteria are to blame:

• Lyme disease is spread via Borrelia bacteria, including Borrelia burgdorferi
• RMSF infections are caused by Rickettsia rickettsii, an entirely different type of bacterium [9]

Different tick species cause each infection and none of the seven tick species living throughout the contiguous US carry both Borrelia and Rickettsia bacteria. So knowing where Lyme disease is common and where RMSF is common is important. Also, having familiarity with the tick populations living in your region and the bacteria they carry can help you rule out each bacteria during diagnosis. [10]

Lyme-carrying ticks include:

• Blacklegged tick
• Western blacklegged tick

RMSF-transmitting tick species are the:

• American dog tick
• Brown dog tick
• Gulf Coast tick
• Rocky Mountain wood tick

Treatment

Both Lyme disease and RMSF can only be eradicated using antibiotic medications. However, the antibiotics prescribed depend upon the age, pregnancy status, and health history of the patient, and anyone experiencing symptoms of either illness should expect to be prescribed: [4]

• Doxycycline for adult infections
• Amoxicillin for illness in children
• Ceftriaxone for pregnant patients

While your healthcare provider will primarily prescribe a course of antibiotics to eliminate the bacteria, they may also recommend over-the-counter (OTC) medications or other remedies, like:

• Tylenol or another OTC treatment for pain relief or fever reduction
• Hydrocortisone or another anti-itch cream to soothe itching rashes
• Melatonin or another sleep aid to help patients fall asleep

Fight tick-borne illnesses with help from Everlywell

Key differences in Lyme disease vs. Rocky Mountain Spotted Fever can help patients and medical professionals determine a diagnosis. But, if you suspect that you may have a tick-borne illness, you can take action by getting a laboratory test done or taking a test from the comfort of home with a Lyme disease test kit from Everlywell.

Using an at-home test kit can help you and your healthcare provider determine your diagnosis, and completing an Everlywell test is easy:

• Register your test kit online using the unique code on the package
• Collect a finger prick sample and send it to us using prepaid postage
• Access your results via our secure online platform in just a few days

Everlywell offers digital healthcare solutions designed for you—we’re putting the power of diagnosis, early intervention, and prevention into your hands, giving you access to high-quality testing when you need it most.

Related content

What Are the Long-Term Effects of Lyme Disease?

How is Lyme Disease Diagnosed?

Where Is Lyme Disease Common?

Stages of Lyme Disease Explained

References

1. Tickborne Diseases of the United States. US Centers for Disease Control and Prevention. URL. Accessed July 13, 2022.
2. Division of Vector-Borne Diseases. US Centers for Disease Control and Prevention. URL. Accessed July 13, 2022.
3. Lyme Disease. US Centers for Disease Control and Prevention. URL. Accessed July 13, 2022.
4. Lyme Disease. National Library of Medicine. URL. Accessed July 13, 2022.
5. Preventing Tick Bites on People. US Centers for Disease Control and Prevention. URL. Accessed July 13, 2022.
6. Rocky Mountain Spotted Fever (RMSF). US Centers for Disease Control and Prevention. URL. Accessed July 13, 2022.
7. RMSF – Epidemiology and Statistics. US Centers for Disease Control and Prevention. URL. Accessed July 13, 2022.
8. Lyme Disease Rashes and Look-Alikes. US Centers for Disease Control and Prevention. URL. Accessed July 13, 2022.
9. Rocky Mountain Spotted Fever. National Institutes of Health. URL. Accessed July 13, 2022.
10. Regions Where ticks Live US Centers for Disease Control and Prevention.. URL. Accessed July 13, 2022.