When Lyme disease became a reportable disease in 1987, the Washington State Department of Health (DOH) set up a surveillance system to monitor, tabulate, and analyze case reports. Because there is no gold standard for diagnosing Lyme disease, every case report of suspected Lyme disease must be analyzed to determine whether it fits the surveillance case definition for Lyme disease that has been established by the Centers for Disease Control and Prevention (CDC) (Table 5). Cases that meet the CDC criteria will be referred to as “confirmed” cases in this monograph. These criteria tend to be strict (i.e., specific) because many of the symptoms of Lyme disease are vague or mimic other illnesses. If surveillance criteria were less strict (i.e., more sensitive), many more persons without the disease would also be included and the number of confirmed cases of Lyme disease would be falsely elevated. Strict surveillance criteria may result in the exclusion of some atypical cases, but, given the low incidence of the disease in Washington, they provide more accurate estimates of incidence.

Clinicians should keep in mind that the CDC developed the surveillance case definition to improve accuracy of case reporting for public health surveillance purposes. In diagnosing individual patients, health care providers will need to use clinical judgement in addition to the objective findings required in the CDC case definition.

Table 5

Lyme Diseases National Surveillance Case Definition

Lyme disease is a systemic, tick-borne disease with protean manifestations, including dermatologic, rheumatologic, neurologic, and cardiac abnormalities. The best clinical marker for the disease is the initial skin lesion, erythema migrans (EM), that occurs in 60% to 80% of patients.

A case of Lyme disease is defined as follows: A person with erythema migrans; or A person with at least one late manifestation and laboratory confirmation of infection. NOTE: Epidemiologic case definition intended for serveillance purposes only.

General Clinical Definitions:

1. Erythema Migrans (EM): For purposes of surveillance, EM is a skin lesion that typically begins as a red macule or papule and expands over a period of days or weeks to form a large round lesion, often with partial central clearing. A single primary lesion must reach at least 5 cm in size. Secondary lesions may also occur. Annular lesions occurring within several hours of a tick bite represent hypersensitivity reactions and do not qualify as EM. In most patients, the expanding EM lesion is accompanied by other acute symptoms, particularly fatigue, fever, headache, mild stiff neck, arthralgias or myalgias. These symptoms are typically intermittent. The diagnosis of EM must be made by a physician. Laboratory confirmation is recommended for persons with no known exposure.

2. Late Manifestations These include any of the following when an alternate explanation is not found. a. Musculoskeletal system Recurrent, brief attacks (weeks or months) of objective joint swelling in one or a few joints sometimes followed by chronic arthritis in one or a few joints. Manifestations not considered as criteria for diagnosis include chronic progressice arthritis not preceded by brief attacks and chronic symmetrical polyarthritis. Additionally, arthralgias, myalgias, or fibromyalgia syndromes alone are not accepted as criteria for musculoskeletal involvement. b. Nervous system Lymphocytic meningitis, cranial neuritis, particularly facial palsy (may be bilateral), radiculoneuropathy or rarely, encephalomyelitis alone or in combination. Encephalomyelitis must be demonstrated by showing antibody production against B. burgdorferi in the cerebrospinal fluid (CSF), evidenced by a higher titer of antibody in CSF than in serum. Headache, fatigue, paresthesis, or mild stiff neck alone are not criteria for neurologic involvement. c. Cardiovascular system Acute onset, high grade (2nd or 3rd degree) atrioventricular conduction defects that resolve in days to weeks and are sometimes associated with myocarditis. Palpations, bradycardia, bundle branch block, or myocarditis alone are not accepted as criteria for cardiovascular involvement.

3. Exposure Exposure is defined as having been in wooded, brushy, or grassy areas (potential tick habitats) in an endemic county no more than 30 days prior to the onset of EM. A history of tick bite is not required.

4. Endemic county An endemic county is one in which at least 2 definite cases have been previously acquired or a county in which established populations of a tick vector are infected with B. burgdorferi.

5. Laboratory confirmation Laboratory confirmation of infection with B. burgdorferi is established by: Isolation of Borrelia burgdorferi from a clinical specimen or Demonstration of diagnostic immunoglobulin M or imunoglobulin G antibodies to B. burgdorferi in serum or cerebrospinal fluid (CSF). A two-test approach using a sensitive enzyme immunoassay or immunofluorescence antibody followed by Western blot is recommended.