As the H5N1 bird flu virus continues to spread among animals, the discovery of infected rats in Riverside County provides another example of the virus' penchant for surprise.

Before future studies would uncover a link between Nipah outbreaks and the felling of native forests for the purposes of fruit plantations, more than 1 million pigs are culled to quell an outbreak that leads to the deaths of 105 people.

More recently, a fox in North Dakota, a bobcat in the state of Washington, a cat in Oregon and a harbor seal in Massachusetts have been infected.