Cats live in nearly 80 million American households, but a new study suggests nearly one out of fifteen cats are infected with a common parasite, and one out of five infected cats can transmit it to humans. ↧ 1 in 15 household cats may carry 'Beaver Fever' which can infect hu... A new study published in the Public Library of Science suggests nearly one out of 15 cats are infected with a common parasite.