Spillover: the powerful, prescient book that predicted the Covid-19 coronavirus pandemic.

by David Quammen

Over those twenty years, mammal by mammal, tick by tick, Ostfeld and his team collected an enormous body of information, and the work continues. They use Sherman live traps (from the H. B. Sherman company, of Tallahassee, a venerable supplier) baited with oats and set out on the forest floor. They release most of the captured animals alive, after a brief examination to check body condition and remove ticks. Small mammal biologists like him, for whom trap-and-release protocols are the daily routine of data gathering, tend to become highly adept—gentle but efficient—at handling live rodents. Ostfeld’s group has found that, in about one minute of close scrutiny, they can detect 90 percent of the ticks on a mouse. (They measured their own field-exam thoroughness by taking some mice into captivity after the one-minute checkover, holding them captive, and waiting for all ticks to fall off into a pan of water beneath the cage. Then they sorted the ticks from the mouse shit and other detritus—“a messy and challenging task,”44 Ostfeld testified—and counted this fuller total for comparison with what had been seen in the field.) For chipmunks, the method of quick visual inspection worked almost as well. On other small mammals, including squirrels and shrews, the tick burdens were higher and harder to count, but Ostfeld’s group could still make well-informed estimates. Larval ticks are minuscule and even a tiny masked shrew, weighing only five grams (about the same as two dimes), carr...

Tick census!