Passage4 In this file photo,a Lowland Gorilla is seen in the Kahuzi-Biega National Park in South Kivu,eastern Democrati Republic of Congo on Nov.5,2012. Disease and the Spillover Effect For David Quammen,the story ofthe 13 dead gorillas outside the Gabon village shows how new infectious diseases are connecting humans and animals. Mr.Quammen wrote a book called Spillover:Animal Infections and the Next Human Pandemic.This book describes how these diseases jump,or move,from animals to people at an increasingrate. Rats carry many different diseases The fleas on rats then transmit disease to humans. This is not new. Bubonic plague,for example,jumped from rodents like rats to humans through infected fleas,a tiny biting insect.That plague killed as many as 60 percent of Europeans in the 14th centuryPassage 4 3 / 5 Disease and the Spillover Effect For David Quammen, the story of the 13 dead gorillas outside the Gabon village shows how new infectious diseases are connecting humans and animals. Mr. Quammen wrote a book called Spillover: Animal Infections and the Next Human Pandemic. This book describes how these diseases jump, or move, from animals to people at an increasing rate. This is not new. Bubonic plague, for example, jumped from rodents like rats to humans through infected fleas, a tiny biting insect. That plague killed as many as 60 percent of Europeans in the 14th century. In this file photo, a Lowland Gorilla is seen in the Kahuzi-Biega National Park in South Kivu, eastern Democratic Republic of Congo on Nov. 5, 2012. Rats carry many different diseases. The fleas on rats then transmit disease to humans