The outbreak of a deadly virus or disease has long been a favorite delivery method of apocalyptic ruin by storytellers. Many films and television shows have explored the idea of the end of the world via outbreak, and some have even done it pretty well.

Organizations like the World Heath Organization (WHO) and Center for Disease Control and Prevention (CDC) are semi-mysterious entities that house the world’s most devastating pathogens and, as such, are prime candidates for modern apocalyptic fiction. While not every apocalyptic pathogen film involves the CDC or WHO, they all have some key commonalities: a virus, an outbreak, and a need for a cure.

It’s important to understand that none of these films present realistic scenarios. They’re all flawed in their own way, supplemented by movie magic to make for a better story. That said, there are some interesting concepts at play, so let’s take a look at a few relatively recent films that range from “pretty damn ridiculous” to “plausible…sorta.” To be clear, this is by no means an exhaustive list. A preliminary count revealed well over 70 films dabbling in pathogens. These are simply a starting point.

5. I Am Legend’s Vamp Virus

Will Smith’s 2007 film is adapted from the 1954 Richard Matheson novel of the same name. The novel also inspired a slew of other films, including Omega Man and The Last Man on Earth (the Vincent Price movie, not the Will Forte show). Like the novel, the film version of I Am Legend follows Robert Neville, the lone survivor of a virus that wiped out the population and turned healthy people into, um, vampires — there’s a reason this film nabbed the bottom spot. Immune to the disease, Neville tries to develop a cure from his own blood.

Popular Mechanics spoke to virologist Dr. W. Ian Lipkin to find out whether or not this turn of events was plausible and, well, suffice to say it’s not just the vampirism that’s the stuff of fiction.

“Viruses don’t mutate and become airborne,” Lipkin told Popular Mechanics. “They typically fall into a couple of different categories — respiratory, STDs and vector-borne like insects, ticks and mosquitoes. They don’t change from tick-borne to pneumonic. They just don’t do that.”

Also more fiction than science? Neville’s immunity despite not having contact with the disease, along with any attempt to engineer a cure from his blood alone.

4. 28 Days Later’s Rage Virus

Rabies has been a part of zombie lore for decades, and it’s apparent in 28 Days Later, which features a horrifying brand of very quick and very pissed zombies. The Rage Virus is borne of an attempt to eradicate or at least inhibit anger and violence in humans. Naturally, things go wrong and the virus begins to take over the world, sparing only a few.

The mortality rate of the virus is unprecedented, obviously, but perhaps the most implausible piece of the pathogenic puzzle is the rate of transmission. In 28 Days Later, the virus takes hold in a matter of seconds, which just isn’t likely given what we know about pathogens.

We’ll talk more about transmission and infection rates with World War Z, but as Harold Varmus points out in The New York Times, the virus in 28 Days Later operates as a metaphor in a larger societal context. The film ignores the known boundaries of micro and molecular biology as well as virology — for the purpose of talking about rage as it exists in our world through the lens of a zombie film.

3. World War Z’s Zombie Virus

Another case of quick infection and fast zombies, World War Z also doesn’t adhere to the scientific principles of microbiology, but it does cover some plausible territory in a different way. Biophysicist Scott Forth took a look at the film for Vulture, and though he found the inevitable inaccuracies, he also uncovered a fair few things that rang true.

First, though: infection rates. Forth found that the twelve seconds it took to get from “bitten” to “full-on zombie mode” was way too fast to be realistic.

“In reality, it takes about a minute or so for blood to circulate through the body in an average person,” he says. “And if the infection is viral or biological, it would take quite a bit longer for the machinery of those pathogens to start inducing an immune response.”

But in the realm of possibility? That cure. It sort of makes sense that infecting healthy humans with a disease that would make them ping on the “undesirable prey” radar for the undead. That said, Forth notes that infecting a bunch of people with meningitis is sort of short-sighted and also probably a very bad idea in its own right.

2. Outbreak’s Motaba Virus

Motaba, the virus featured in the 1995 film Outbreak, is based on Ebola. As such, there’s a degree of plausibility. It’s a fictional virus, but like Contagion’s MEV-1, it has real-world inspiration.

Motaba is deadlier than Ebola but presents similar symptoms and, like Ebola, can be transmitted from animals to humans. Motaba has also apparently mutated and become airborne, making it much more dangerous because it can spread much more quickly and easily. It’s worth nothing, though, that the CDC says that this is highly unlikely in the case of Motaba’s real-world inspiration. Though viruses mutate all the time, it would be very unlikely to see one mutate in a way that changed how it’s transmitted. See also: Lipkin’s take on the I Am Legend virus.

Though its Motaba virus isn’t totally based on reality, it isn’t plucked entirely from fiction, either. It’s not an impossibility like some of the other films, and Outbreak wins points for its depiction of the spread of an infectious disease, along with “level four biosafety precautions.”

Like several other outbreak films, Outbreak arrives at its cure too quickly to be plausible (hours versus months or, more likely, even years), but the virus itself has some merit, if only because its origins are very real.

1. Contagion’s MEV-1 Virus

The 2011 film Contagion follows the extremely deadly outbreak of a virus that claims millions of lives. The fictional MEV-1 virus has some plausible elements, likely because it was modeled off of the very real Nipah virus and inspired by real outbreaks and pandemics. Interestingly enough, the technical consultant for the film, Dr. W. Ian Lipkin, is the same guy who helped bust I Am Legend for Popular Mechanics.

Nipah’s jump from animals to humans is a key element that influenced MEV-1, but the spread of the disease bears very little resemblance to Nipah. CDC experts told PBS that the transmission more closely resembles the SARS outbreak or the H1N1 pandemic. The same experts also busted this particular viral compound, saying, “Influenza and Nipah have incompatible genomes that are not capable of recombination in nature.”

The experts also say that fictional researchers arrived at their cure more quickly than is strictly realistic, but they told PBS that the method for “tracing” the disease is a slice of real-life CDC work.

Though the virus isn’t totally realistic and neither is the spread of the virus itself, Contagion is made up of elements that are plausible and plucked from the world of very deadly viruses. An outbreak on the level of MEV-1 is completely unprecedented, but if a virus were to find the right conditions, both SARS and H1N1 are proof that the degree to which humans moving across the globe can make a virus spread scary fast.

For now, though, we’ll rest easy with the knowledge that all of these films got it wrong in one way or another.