Why 'The Walking Dead' Virus Doesn't Affect Animals, According to Science

The zombie virus on The Walking Dead is exclusive to humans, a detail which can be justified through science.

"Some viruses are very species-specific," Tara Smith, a microbiologist and infectious disease epidemiologist at Kent State University in Ohio, told LoveScience. "For example, measles and small pox, humans seem to be the only host for those, they don't jump species."

While this virus is human specific and cannot plague other species, not all viruses can only be carried by one species. "One of the ways we think Ebola may have spread into people, especially the 2014 West African people, was contact with bats or potentially eating bats, we're not 100 percent sure," Smith said. "Either way, bats seem to be the reservoir, but they don't seem to be affected by it. It's not symptomatic in them, but it causes huge symptoms in humans."

For that reason, Smith suggests humans "try to minimize time spent in close contact with [their] animals," especially in worlds like The Walking Dead's.

While Daryl's new dog is not affected by The Walking Dead virus, nor are the pigs from the prison days, it could have been possible for select species of animals to be affected while others remain immune. "Some flu viruses can affect a broad range of species, and we saw that with H1N1 outbreak in 2009," Smith said. "So, whatever it is, it still seems to be human specific, otherwise you would expect to see zombie animals."

There is a scientific breakdown which can be simplified for the average person to understand why the zombie virus (or real life viruses) work in such ways in regards to being species exclusive.

"Viruses typically have a tropism — that means they can only bind to certain types of cells," Smith said. "Sometimes the protein they have that would bind to cells might be ubiquitous to all animals or all mammalian species, or it can be really specific."

The Walking Dead airs Sundays at 9 pm ET. Fear the Walking Dead will return for its fifth season in 2019. For complete coverage and insider info all year long, follow @BrandonDavisBD on Twitter and watch ComicBook.com's After The Dead each Sunday night following new episodes.