It’s the Heat and the Humidity, New Study Finds: Why Lyme Disease is Common in the North, Rare in the SouthWhen it's hot and not too muggy, Lyme disease-bearing ticks hide out where people don't tread. Scientists say that's why the illness is rare in the South, and may eventually fade out along the Mason-Dixon line.
The ticks that transmit Lyme disease to people die of dehydration when exposed to a combination of high temperature and lowered humidity, a new USGS-led study has found. In an earlier related study, the researchers found that southern black-legged ticks, unlike northern ones, usually stay hidden under a layer of leaves, where they are less likely to encounter people. The research group, whose findings were published Jan. 11 in the journal PLOS ONE, hypothesizes that southern ticks typically shelter under leaves to retain moisture, and that this behavior is a key reason why Lyme disease is very uncommon in the South.