The “bugs” of late summer are biting. The nation is having its worst West Nile virus season in a decade, and up to 10,000 people who stayed in California cabins are at risk of hantavirus. A second case of bubonic plague in the West has been confirmed — in a girl in Colorado — and scientists fear that a bumper crop of ticks could spread Lyme disease, the nation’s most common bug-borne malady.