Misdiagnosis of early Lyme disease as the summer flu

Abstract

Lyme disease is often identified by the hallmark erythema migrans rash, but not all early cases present with a rash. In other cases the rash may be unseen or unrecognized by a physician. In these situations, Lyme disease is difficult to diagnose because it masquerades as a non-specific viral-like illness. The seasonal peak of Lyme disease ranging from May through September overlaps with that of viral illnesses such as enteroviral infections, West Nile virus, and in rare years such as 2009, early influenza season. We present a case of a patient with Lyme disease who was initially misdiagnosed with influenza A during the summer of 2009. Because of the diagnostic importance of recognizing the erythema migrans rash, physicians in endemic regions should always ask about new rashes or skin lesions and perform a thorough physical examination when patients present over the summer with viral-like symptoms. Even when no rash is evident, Lyme disease should be considered if these symptoms persist or worsen without a specific diagnosis.

Keywords: Lyme disease; diagnosis; summer flu; viral-like illness.

Figure 1

Erythema migrans lesions observed upon physical examination of patient. Primary lesion behind knee (left), along with two disseminated lesions (middle and right).

Figure 2

Google Trends graph depicting tendency over time to search for Lyme disease and cough. Searches for Lyme disease (blue) and cough (red). Cough used as a search term to capture respiratory viral infections more likely to manifest during the winter months. In 2009, searches for cough increased earlier than usual, corresponding to an early flu season and thus overlapping with Lyme disease season. Search volume index refers to the number of searches for these terms, relative to the total number of searches done on Google over time. News reference volume refers to the number of times these terms appeared in a Google News story.