Pa. Lyme disease cases near historic highs in Allegheny, Westmoreland counties - TribLIVE.com

What the report says

TribLIVE reports that Lyme disease cases in Western Pennsylvania are again approaching historic levels, with preliminary Pennsylvania Department of Health data showing more than 1,300 cases this year across Allegheny and Westmoreland counties. The outlet said Allegheny County has recorded 827 cases and Westmoreland County 498, following a statewide 15-year high of 18,749 cases last year.

The report places the local numbers within a broader rise in tick-borne illness. Citing federal data, TribLIVE notes that vector-borne disease cases increased sharply nationally between 2004 and 2016, and that tick bites accounted for most of those cases. Pennsylvania has been a major share of the national Lyme burden, with CDC figures showing the state accounted for more than a quarter of U.S. cases from 2016 through 2019.

Researchers quoted by TribLIVE said tick numbers and disease risk are shaped by hosts, habitat and weather. Danielle Tufts of the University of Pittsburgh School of Public Health, whose team has been tracking ticks since 2022, said longer warm periods can give ticks more opportunities to feed. Nicole Chinnici of the Pennsylvania Tick Research Lab said local tick density at monitored sites has fluctuated but has not shown a clear increase.

The article also highlights changing climate patterns, suburban development near wooded areas and increased outdoor activity as factors that can increase human exposure. Researchers said white-footed mice are a key reservoir for Lyme bacteria, while deer help sustain tick populations but do not transmit the pathogen to ticks. TribLIVE also reported that the Pennsylvania Tick Research Lab has found disease-causing organisms in 28% of more than 141,000 resident-submitted ticks tested.