Scientists at the National Center for Atmospheric Research and the U.S. Centers for Disease Control recently explored the relationship between the reports of Lyme disease and weather observations. They found that warmer temperatures, higher humidity and less rain are correlated with an earlier start and peak of the Lyme disease season.
The start of the Lyme disease season begins in late May on average and lasts for about 14 weeks. An above average amount of precipitation from the start of the year tends to result in a later beginning of the Lyme disease season. An earlier start to the season is associated with more days with temperatures above 50 degrees, except for the most northern regions of the U.S.
Deer ticks carry Lyme disease and can infect humans when they bite us. The disease is found predominately in Wisconsin, Minnesota and the northeastern United States.
The ticks that commonly spread the disease develop faster with warmer temperatures, and they are more active in feeding with warmer temperatures, higher humidity and a lack of heavy precipitation. Of course, these are times many people seek the outdoors.
Weather conditions not only affect the tick life cycle and our outdoor habits, but also the population of the ticks’ primary host — the white-footed mouse. A dry summer can result in less vegetation that is the food supply for the mice. This can result in a reduced population of mice, reducing the tick population and thus the cases of Lyme disease.
The correlation between weather and the start of Lyme disease season is strong enough that one can forecast the start of the season by analyzing the daily temperatures for the first 10 weeks of the year. Unfortunately, there are few correlations that support predicting the end of a particular Lyme disease season.