The District currently tests for several tick-borne diseases., including Borrelia burgdorferi, which causes Lyme disease, and Borrelia miyamotoi, which causes a similar, less-common tick-borne disease.
The results of these tests are reported as the minimum infection rate, or MIR. This is a way of describing the proportion of ticks tested that are infected with a particular pathogen. The table shows the MIR for Borrelia burgdorferi, the MIR for Borrelia miyamotoi, and the total MIR for Borrelia bacteria. These are reported for each park surveyed (with the exception of parks where there were not enough ticks collected to complete testing), and for the parks as a whole.
A MIR of 2-3% is considered normal for our county, and does not indicate an elevated level of risk.
Please see the attached spreadsheet for the latest tick-borne disease surveillance data for 2014-2015.
The MIR with Borellia bacteria for Ixodes pacificus (western black legged tick) in parks in San Mateo County was 1.49%. A MIR of 2-3% is considered normal for our county, and does not indicate an elevated level of risk.