About the Lyme Disease data

This page provides general information about Lyme disease and measures developed by the Minnesota Environmental Public Health Tracking (MN Tracking) Program. For more information about these data, contact MN Public Health Data Access.

Information on this page:

What these data tell us:

For confirmed human Lyme disease cases in Minnesota:

  • The numbers of Lyme disease by year, month, gender, or age group in Minnesota.
  • If a segment of a population is at higher risk for Lyme disease.
  • How the disease incidence is changing over time.

How we can use these data:

  • Provide information to the public about Lyme disease in Minnesota.
  • State and local partners can use these data for program planning and evaluation.
  • Inform prevention guidelines for targeted public awareness & prevention campaigns during peak tick season.
  • MDH Vectorborne Disease Unit and the MDH Climate and Health Program can use these data to inform their programs.

What these data can not tell us:

  • The total burden of Lyme disease in a population, since not all Lyme disease cases are diagnosed or reported.
  • Where the person was when they were exposed to an infected tick.
  • The number or rate of occupationally-acquired cases of Lyme disease in Minnesota.
  • How much climate change has influenced the changes in Lyme disease.

The source of the data:

  • Lyme disease is a notifiable condition. Data is collected by the MDH Vectorborne Diseases Unit under Minnesota statute 4605.7040 B.

How the measures are calculated:

Number: The number indicates the total number of confirmed human cases of Lyme disease.

Maps: The map of Lyme disease by county is based on the cumulative incidence (per 100,000 population) of Lyme disease cases in Minnesota during the three time periods. Cases are categorized by patient's county of residence.

The map of tick-borne disease risk is based on the average incidence (cases/100,000 population) of Lyme disease, human anaplasmosis, and babesiosis cases in Minnesota from 2007-2013. Cases are categorized by patient's county of residence, which may not represent exposure location.

How Lyme disease cases are identified:

Potential cases are reported to the Minnesota Department of Health by physicians and diagnostic laboratories. To be considered a confirmed case of Lyme disease for surveillance purposes, there must be:

  • A case of erythema migrans (EM) with a known exposure (been in wooded or brushy areas in the last 30 days), OR
  • A case of EM with laboratory evidence of infection and without a known exposure, OR
  • A case with at least one late manifestation that has laboratory evidence of infection.

The limitations of the data:

  • Minnesotans still need to see a physician and be diagnosed with Lyme disease to be considered a case. Those people who do not seek medical care will not be included in the case count.
  • Under reporting Lyme disease is a significant concern for data quality. The CDC recently released a report estimating the true Lyme disease case count to be ten times higher than officially reported due to under reporting. The MDH Vectorborne Disease Unit did a similar assessment in an endemic county and found there were almost three times more cases than reported. MDH does not conduct regular audits or complete reviews to look for unreported cases, so missed cases are possible.

More technical information about the data:

To learn more about Lyme disease, contact the MDH Vectorborne Disease Unit. For more information about the data and measures developed by the MN Tracking Program, contact the Data Access portal.