Nearly half of all counties in the US are now home to ticks that carry Lyme disease, including areas where they'd never before been documented, researchers at the CDC report in the Journal of Medical Entomology. That's up from 30% of counties in 1998, with the Guardian reporting that the number of Lyme disease incidents has tripled in the US since the '90s. The biggest increases were seen in northern and northeastern states, reports CBS News, which singles out Minnesota, New York, Ohio, Vermont, and Wisconsin. It's not surprising, then, that while some 30,000 cases of Lyme disease are reported annually, the real figure is estimated at a staggering 330,000 people every year.
While Lyme disease continues to be fairly easy to treat via antibiotics, if left untreated it can lead to serious symptoms, including chronic joint inflammation and even heart and neurological problems years after infection, reports the CDC, which adds that the best preventive measures are removing ticks as quickly as possible and applying pesticides. Biologists blame reforestation, growing deer populations, and climate change for the fast spread of ticks that carry Lyme disease, reports the Guardian, and the researchers note in a press release the rise of the blacklegged tick (Ixodes scapularis) in particular. (Warmer autumns allow ticks more time to feed and infest.)