Stephen Reiss/for NPR[/caption] Keesing and Ostfeld, who have studied Lyme for more than 20 years, have come up with an early warning system for the disease. They can predict how many cases there will be a year in advance by looking at one key measurement: Count the mice the year before. The number of critters scampering around the forest in the summer correlates to the Lyme cases the following summer, they've reported.
The explanation is simple: Mice are highly efficient transmitters of Lyme. They infect up to 95 percent of ticks that feed on them. Mice are responsible for infecting the majority of ticks carrying Lyme in the Northeast. And ticks love mice. "An individual mouse might have 50, 60, even 100 ticks covering its ears and face," Ostfeld says.
So that mouse plague last year means there is going to be a Lyme plague this year. "Yep. I'm sorry to say that's the scenario we're expecting," Ostfeld says.
He's not exactly sure which parts of the Northeast will be at highest risk.But wherever Lyme exists, people should be vigilant, says epidemiologist Kiersten Kugeler at the Centers for Disease Control and Prevention.
"Whether it's a bad season or not, there's still going to be a lot of human cases of tick-borne diseases," she says. "What's important for people to know is that the ticks are spreading to new areas — and tick-borne diseases are coming with them."