Lyme disease, caused by the bacterium Borrelia burgdorferi, is the most common vector-borne illness reported in the mainland U.S. The increasing spread of Lyme disease across the continental United States often leads to questions about its presence in geographically isolated areas like Hawaii. This concern is particularly relevant for residents who travel frequently and for new arrivals to the islands. To understand the actual risk, it is necessary to examine the official reports on disease occurrence and the specific species of ticks established in the Hawaiian ecosystem.
Status of Lyme Disease in Hawaii
The Hawaii State Department of Health (DOH) maintains a clear position regarding the local risk of contracting Lyme disease. The state considers Lyme disease to be non-endemic, meaning there is no established cycle of transmission occurring naturally within the islands.
Cases of Lyme disease are reported in Hawaii, but nearly all of these are classified as imported cases. An imported case means the individual was infected with the Borrelia burgdorferi bacterium while traveling or living in an endemic area outside of Hawaii, such as the Northeast or Midwest U.S., before their symptoms appeared or before they were diagnosed after arriving in the state.
The number of reported cases in the state reflects this travel-related exposure rather than local transmission. While the disease is a nationally notifiable condition, the low incidence and lack of a competent local vector firmly place Hawaii in a low-risk category for autochthonous, or locally acquired, infection.
The Tick Vector Landscape in Hawaii
Lyme disease is transmitted almost exclusively by ticks belonging to the Ixodes genus, specifically the blacklegged tick, Ixodes scapularis, in the Eastern U.S. and the western blacklegged tick, Ixodes pacificus, in the West. Surveillance data from the Hawaii Vector Control Branch confirms that these primary vectors are not established in the state.
Ticks are present in Hawaii, but they are different species that do not effectively transmit the Lyme bacterium. The most common species are the Brown Dog Tick (Rhipicephalus sanguineus) and the Spinose Ear Tick (Otobius megnini). While the Brown Dog Tick is widely distributed globally and can carry other pathogens, it has not been confirmed as a competent vector for Borrelia burgdorferi.
A tick species must be able to acquire the pathogen from an infected host, maintain it through its molting stages, and then transmit it to a new host to be a competent vector. Ticks outside of the Ixodes genus, such as Rhipicephalus, generally fail this transmission cycle for Lyme disease, which is why their presence does not create a local transmission risk. The current tick fauna in Hawaii therefore serves as a natural barrier to the establishment of the Lyme disease cycle.
Diagnostic Challenges and Public Health Considerations
Since local physicians and specialists rarely encounter locally acquired cases, there is a possibility for delayed diagnosis or misdiagnosis when a patient presents with an imported infection. Symptoms of early Lyme disease, such as fever, fatigue, and headache, can be easily mistaken for other common viral or bacterial illnesses, particularly in a low-incidence area where the disease is not top-of-mind.
The primary risk group for Lyme disease in Hawaii remains individuals who have traveled to or recently moved from endemic regions. This includes military personnel and their families, as well as tourists and residents returning from the mainland. The low prior-probability of a local case means that clinicians must rely heavily on patient travel history and clinical presentation to suspect a Lyme disease diagnosis.
The Hawaii DOH maintains surveillance efforts to monitor for changes in tick populations or the potential introduction of new disease vectors. Public health efforts focus on educating both the public and the medical community about the distinction between imported and local cases.