An Influenza-like Illness that is Not Influenza

This case study reviews best practices for diagnosing and treating Lyme disease.

Case study: You are wrapping up clinic in the afternoon, when you see one of your long-time patients in the waiting room.  Bob is a relatively healthy 57-year-old man with a history of well-controlled hypertension. You saw him within the last month and made some adjustments to his medications, but you did not expect to see him back this soon.

When you walk into the examining room, Bob greets you and tells you that he is doing well with his blood pressure. But he has now developed a new-onset fever, headaches, and muscle pain. He is concerned because he feels much worse than he has in the past with these symptoms, and he skipped his flu vaccine this year. What do you do next?

Obviously, the differential diagnosis for these symptoms is vast. Bob could have an infectious disease brought on by a virus, bacteria, or parasite. He could have an underlying malignancy or a drug reaction from his new medication. Your next step is to gather more data by doing a physical exam. On exam, Bob is febrile and slightly tachycardic. His breath sounds are clear; he has no evidence of bruising or bleeding, and no abdominal pain. However, you notice a circular red rash with a central clearing at Bob’s ankle. What do you ask Bob?

You ask Bob if he has had a recent tick bite. A circular red rash with a central clearing is erythema migrans – the pathognomonic sign of Lyme disease. In early stages, the rash may appear like a solid red papule. Given time, the untreated rash will often increase in size and develop a central clearing. Solid red rashes may also be caused by other tick-borne illnesses, so remain vigilant.  You obtain serologies to test for Lyme disease, but given your high index of suspicion for Lyme disease and the fact that you are practicing in a Lyme endemic part of the country, you preemptively treat the patient.

States where Lyme disease is common include Connecticut, Delaware, DC, Maine, Maryland, Massachusetts, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, Virginia, West Virginia, and Wisconsin.[i] People can become infected with Lyme disease in other states if they have traveled to Lyme endemic areas. So remember to ask about travel history and recent tick exposure.

Professional guidelines recommend that providers start high-risk patients on antibiotic treatment even before receiving the final results from laboratory tests. Lyme disease can be prevented by administering a single 200 mg dose of doxycycline within 72 hours of an Ixodes tick bite.[ii] For patients like Bob, a complete course of oral doxycycline is necessary.[iii] Counsel him to take his antibiotics as prescribed and to finish the entire course of treatment in a timely manner.  Recommend that your patients wear long sleeve shirts and pants when they are in forested areas and to check themselves for ticks. Anti-tick sprays can also be effective preventative measures. What if Bob fails to improve or relapses? See what the author would do in the comments section below. Weigh in with your thoughts and join the conversation. 

[i] Centers for Disease Control. Lyme Disease Statistics. Centers for Disease Control Website. Updated November 21, 2016. Accessed February 9, 2017.

[ii] Nadelman RB, Nowakowski J, Fish D, et al. Prophylaxis with single-dose doxycycline for the prevention of Lyme disease after an Ixodes scapularis tick bite. N Engl J Med. 2001;345(2):79-84.

[iii] Wormser GP, Ramanathan R, Nowakowski J, et al. Duration of antibiotic therapy for early Lyme disease. A randomized, double-blind, placebo-controlled trial. Ann Intern Med. 2003;138(9):697-704.


Dr. V. Silverstein
Durham, NC


Would you like to join the discussion? Feel free to contribute!

  1. Dr. V. Silverstein

    February 16, 2017 at 10:06 am

    If Bob fails to improve, you should follow up on his serologies and re-consider your diagnosis. It is possible that he was co-infected with another tick-borne disease. It is also possible that his illness was not due to Lyme disease at all. If Bob has recurrent symptoms despite completing a full course of antibiotics, studies show that he is has probably been re-infected with a different strain of Lyme disease and needs to be treated again.

  2. LHART

    February 20, 2017 at 6:43 pm

    I have a new pateint with symptoms. 50 yo, male, avid hunter. No rash, history of many tick bite. Did 2 weeks of doxycycline with old PCP, felt better, then he was switched to a cephalsporin (doesn’t remember which). Does not know why he was switched off. Felt fine for a short period now has fatigue, joint pain, swelling in hands and knees and headaches. FYI – ALL serologies have been negative, including other endemic tick-borne diseases. Screening for lupus and RF also negative. All his inflammatory markers are normal.

    Restarted doxy, two days ago since he seemed to do well on it and will speak to him every couple of days to monitor any changes. Anything else you would recommend. What are your thoughts on “chronic” Lyme or patients that never sero-convert?


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