viruses

Outbreak turns 30

Entertainment, epidemiology, films, Outbreak film, Science, viruses / Kelly Newman / March 14, 2025

Ars chats with epidemiologist Tara Smith about the film’s scientific accuracy and impact over 3 decades.

Dustin Hoffman and Renee Russo starred in this medical disaster thriller. Credit: Warner Bros.

Back in 2020, when the COVID pandemic was still new, everyone was “sheltering in place” and bingeing films and television. Pandemic-related fare proved especially popular, including the 1995 medical disaster-thriller Outbreak, starring Dustin Hoffman. Chalk it up to morbid curiosity, which some researchers have suggested is an evolved response mechanism for dealing with threats by learning from imagined experiences. Outbreak turned 30 this week, making this the perfect time to revisit the film.

(Spoilers for Outbreak abound below.)

Outbreak deals with the re-emergence of a deadly virus called Motaba, 28 years after it first appeared in an African jungle, infecting US soldiers and many others. The US military secretly destroyed the camp to conceal evidence of the virus, a project overseen by Major General Donald McClintock (Donald Sutherland) and Brigadier General William Ford (Morgan Freeman). When it re-emerges in Zaire decades later, a military doctor, Colonel Sam Daniels (Hoffman), takes a team to the afflicted village to investigate, only to find the entire town has died.

Daniels takes blood samples and realizes the villagers had been infected by a deadly new virus. But Ford shrugs off Daniels’ concerns about a potential global spread, not wanting the truth to come out about the bombing of the village nearly 30 years ago. Daniels alerts his estranged ex-wife, Dr. Roberta “Robby” Keough, who works for the Centers for Disease Control and Prevention, about the virus, and she, too, is initially concerned.

Meanwhile, a local monkey is captured and brought to the US as an exotic pet. A smuggler named Jimbo (Patrick Dempsey)—who works at an animal testing facility—tries to sell the monkey to a pet shop owner named Rudy (Daniel Chodos) in the fictional town of Cedar Creek, California. The monkey bites Rudy. Unable to sell the monkey, Jimbo lets it loose in the woods and flies home to Boston. Both Jimbo and his girlfriend (who greets him at Logan Airport and passionately kisses a feverish Jimbo right before he collapses) die from the virus.

Naturally Keough hears about the Boston cases and realizes Daniels was right—the new virus has found its way to American soil. Initially she thinks there aren’t any other cases, but then Rudy’s demise comes to light, along with the death of a hospital technician who became infected after accidentally breaking a vial of Rudy’s blood during testing. When the virus strikes down a cinema filled with moviegoers, Daniels and Keough realize the virus has mutated and become airborne.

This time Ford and a reluctant McClintock can’t afford not to act as the bodies keep piling up. The military declares martial law in the town as Daniels and his fellow scientists race to develop a cure, even as the nefarious McClintock schemes to bomb Cedar Creek to smithereens to contain the virus. The deaths of the residents strike him as a necessary cost to preserve his hopes of developing Motaba as a biological weapon; he dismisses them as “casualties of war.”

Outbreak ended up grossing nearly $190 million worldwide when it was released in March 1995, but critical reviews were mixed. Some loved the medical thriller aspects and quick pacing, while others dismissed it as shallow and improbable. Some of the biggest criticisms of the film came from scientists.

A mixed bag

“Honestly, the science, if you look at it broadly, is not awful,” Tara Smith, an epidemiologist at Kent State University in Ohio, told Ars. “They showed BSL-4 facilities and had a little description of the different levels that you work in. The protagonists respond to an outbreak, they take samples, they bring them back to the lab. They infect some cells, infect some animals, they do some microscopy, although it’s not clear that they’re actually doing electron microscopy, which would be needed to see the virus. But overall, the steps are right.”

Granted, there are plenty of things to nitpick. “There’s a lot of playfulness,” said Smith. “Kevin Spacey [who plays military doctor Lt. Col. Casey Schuler] takes out a fake virus tube and tosses it to Cuba Gooding Jr. [who plays another military doctor, Major Salt]. You don’t play in the BSL-4 laboratories. You just don’t. And a lab tech [who becomes infected] is spinning a centrifuge and doing other things at the same time. Then he opens up the centrifuge and just puts his hand in there and everything breaks. That’s how he gets exposed to the virus. I’ve used a centrifuge hundreds of times. You wait until everything is stopped to open it up. As a trained scientist, those are the things you are told over and over not to do. [The filmmakers] exploit those to drive the plot.”

One of the biggest scientific criticisms is the time compression: the virus multiplies in the body within an hour instead of days; Salt eventually synthesizes a cure in under a minute when this would normally take months; and Keough (who has been infected) recovers almost immediately after being injected with said cure. Smith also noted that scientists identify the two Motaba strains using electron micrographs rather than sequencing them, as would normally be required.

And that whole bit about the Motaba virus liquefying organs just isn’t a thing, according to Smith. “If you read The Hot Zone [Richard Preston’s bestselling 1994 nonfiction thriller], or watch Outbreak and take a shot every time you hear ‘liquefying,’ you would be dead by the end,” she said. “I don’t know how that trope got so established in the media, but you see it every time the Ebola comes up: people are bleeding from their eyes, they’re liquefying. That doesn’t happen. They’re horribly sick. It is an awful virus, but people don’t just melt.”

That said, “I think the biggest [scientific] issue with Outbreak was the whole airborne thing,” said Smith. “Realistically, viruses just don’t change transmission like that.”

Influencing public perceptions

According to Smith, Outbreak may have impacted public perceptions of the 2014–2016 Ebola outbreak—the largest yet seen—fueling widespread fear. “There were very serious people in The New York Times talking about Ebola potentially becoming airborne,” she said. “There was one study where scientists had aerosolized the virus on purpose and given it to pigs and the pigs got infected, which was treated as proof that Ebola could be airborne.”

“That idea that Ebola is super contagious and you can spread it by air—that really originates with Outbreak in 1995, because if you look at the science, it’s just not there,” Smith continued. “Ebola is not that easy to get unless you have close, personal, bodily-fluid-exchanging contact. But people certainly thought it was airborne in 2014–2015, and thought that Ebola was going to cause this huge outbreak in the United States. Of course, we just had a few select cases.”

Smith is currently working on a project that reviews various outbreak stories in popular media and their influence on public perception, particularly when it comes to the origins of those outbreaks. “Where does the virus, fungus, or bacteria come from?” said Smith. “So many films and TV series have used a lab leak origin, where something was made in the laboratory, it escapes, and causes a global pandemic. That’s an important narrative when we talk about the COVID pandemic, because so many people jumped on the lab leak bandwagon as an origin for that. In Outbreak it’s a natural virus, not a lab leak. I don’t think you’d see that if it were re-made today.”

Sam and Salt find the information they’re looking for. Warner Bros.

Outbreak is often unfavorably compared to another pandemic movie, 2011’s Contagion, of which Smith is naturally a fan. “Contagion is the gold standard [of pandemic movies],” said Smith. “Contagion was done in very close collaboration with a lot of scientists. One of the scientists in the movie is even named for [Columbia University epidemiologist] Ian Lipkin. Scientific accuracy was more important from the start. And there’s a bigger timeframe. These things happen in months rather than days. Even in Contagion, the vaccine was developed quicker than in the COVID pandemic, but at least it was a little bit more realistically done, scarily so when you think about the Jude Law character who was the blogger peddling fake cures—very similar to Ivermectin during the COVID pandemic.”

One might quibble with the science, but as entertainment, after 30 years, the film holds up remarkably well, despite the obvious tropes of action films of the 1990s. (Sam and Salt defying orders and hijacking a military helicopter, then using it to face-off mid-air against a military aircraft deployed to bomb the town out of existence, is just one credibility-straining example.) The talented cast alone makes it worth a rewatch. And for Smith, it was nice to see a strong female epidemiologist as a leading character in Russo’s Bobby Keough. On the whole, “I honestly think Outbreak was fairly good,” she said.

Jennifer is a senior writer at Ars Technica with a particular focus on where science meets culture, covering everything from physics and related interdisciplinary topics to her favorite films and TV series. Jennifer lives in Baltimore with her spouse, physicist Sean M. Carroll, and their two cats, Ariel and Caliban.

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The wasps that tamed viruses

Biology, entomology, Parasitic wasps, Science, syndication, virology, viruses / DJ Henderson / May 10, 2024

Parasitoid wasp — Enlarge / *Xorides praecatorius* is a parasitoid wasp.

If you puncture the ovary of a wasp called Microplitis demolitor, viruses squirt out in vast quantities, shimmering like iridescent blue toothpaste. “It’s very beautiful, and just amazing that there’s so much virus made in there,” says Gaelen Burke, an entomologist at the University of Georgia.

M. demolitor is a parasite that lays its eggs in caterpillars, and the particles in its ovaries are “domesticated” viruses that have been tuned to persist harmlessly in wasps and serve their purposes. The virus particles are injected into the caterpillar through the wasp’s stinger, along with the wasp’s own eggs. The viruses then dump their contents into the caterpillar’s cells, delivering genes that are unlike those in a normal virus. Those genes suppress the caterpillar’s immune system and control its development, turning it into a harmless nursery for the wasp’s young.

The insect world is full of species of parasitic wasps that spend their infancy eating other insects alive. And for reasons that scientists don’t fully understand, they have repeatedly adopted and tamed wild, disease-causing viruses and turned them into biological weapons. Half a dozen examples already are described, and new research hints at many more.

By studying viruses at different stages of domestication, researchers today are untangling how the process unfolds.

Partners in diversification

The quintessential example of a wasp-domesticated virus involves a group called the bracoviruses, which are thought to be descended from a virus that infected a wasp, or its caterpillar host, about 100 million years ago. That ancient virus spliced its DNA into the genome of the wasp. From then on, it was part of the wasp, passed on to each new generation.

Over time, the wasps diversified into new species, and their viruses diversified with them. Bracoviruses are now found in some 50,000 wasp species, including M. demolitor. Other domesticated viruses are descended from different wild viruses that entered wasp genomes at various times.

Researchers debate whether domesticated viruses should be called viruses at all. “Some people say that it’s definitely still a virus; others say it’s integrated, and so it’s a part of the wasp,” says Marcel Dicke, an ecologist at Wageningen University in the Netherlands who described how domesticated viruses indirectly affect plants and other organisms in a 2020 paper in the Annual Review of Entomology.

As the wasp-virus composite evolves, the virus genome becomes scattered through the wasp’s DNA. Some genes decay, but a core set is preserved—those essential for making the original virus’s infectious particles. “The parts are all in these different locations in the wasp genome. But they still can talk to each other. And they still make products that cooperate with each other to make virus particles,” says Michael Strand, an entomologist at the University of Georgia. But instead of containing a complete viral genome, as a wild virus would, domesticated virus particles serve as delivery vehicles for the wasp’s weapons.

Enlarge / Here are the steps in the life of a parasitic wasp that harbors a bracovirus.

Those weapons vary widely. Some are proteins, while others are genes on short segments of DNA. Most bear little resemblance to anything found in wasps or viruses, so it’s unclear where they originated. And they are constantly changing, locked in evolutionary arms races with the defenses of the caterpillars or other hosts.

In many cases, researchers have yet to discover even what the genes and proteins do inside the wasps’ hosts or prove that they function as weapons. But they have untangled some details.

For example, M. demolitor wasps use bracoviruses to deliver a gene called glc1.8 into the immune cells of moth caterpillars. The glc1.8 gene causes the infected immune cells to produce mucus that prevents them from sticking to the wasp’s eggs. Other genes in M. demolitor’s bracoviruses force immune cells to kill themselves, while still others prevent caterpillars from smothering parasites in sheaths of melanin.

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We still don’t understand how one human apparently got bird flu from a cow

bird flu, cattle, CDC, cows, genetic surveillance, H5N1, human case, Infectious disease, mutations, outbreak, pandemic, Science, USDA, viral sequences, viruses / Shannon Garcia / May 4, 2024

Enlarge / Holstein dairy cows in a freestall barn.

The US Department of Agriculture this week posted an unpublished version of its genetic analysis into the spillover and spread of bird flu into US dairy cattle, offering the most complete look yet at the data state and federal investigators have amassed in the unexpected and worrisome outbreak—and what it might mean.

The preprint analysis provides several significant insights into the outbreak—from when it may have actually started, just how much transmission we’re missing, stunning unknowns about the only human infection linked to the outbreak, and how much the virus continues to evolve in cows. The information is critical as flu experts fear the outbreak is heightening the ever-present risk that this wily flu virus will evolve to spread among humans and spark a pandemic.

But, the information hasn’t been easy to come by. Since March 25—when the USDA confirmed for the first time that a herd of US dairy cows had contracted the highly pathogenic avian influenza H5N1 virus—the agency has garnered international criticism for not sharing data quickly or completely. On April 21, the agency dumped over 200 genetic sequences into public databases amid pressure from outside experts. However, many of those sequences lack descriptive metadata, which normally contains basic and key bits of information, like when and where the viral sample was taken. Outside experts don’t have that crucial information, making independent analyses frustratingly limited. Thus, the new USDA analysis—which presumably includes that data—offers the best yet glimpse of the complete information on the outbreak.

Undetected spread

One of the big takeaways is that USDA researchers think the spillover of bird flu from wild birds to cattle began late last year, likely in December. Thus, the virus likely circulated undetected in dairy cows for around four months before the USDA’s March 25 confirmation of an infection in a Texas herd.

This timeline conclusion largely aligns with what outside experts previously gleaned from the limited publicly available data. So, it may not surprise those following the outbreak, but it is worrisome. Months of undetected spread raise significant concerns about the country’s ability to identify and swiftly respond to emerging infectious disease outbreaks—and whether public health responses have moved past the missteps seen in the early stages of the COVID-19 pandemic.

But another big finding from the preprint is how many gaps still exist in our current understanding of the outbreak. To date, the USDA has identified 36 herds in nine states that have been infected with H5N1. The good news from the genetic analysis is that the USDA can draw lines connecting most of them. USDA researchers reported that “direct movement of cattle based upon production practices” seems to explain how H5N1 hopped from the Texas panhandle region—where the initial spillover is thought to have occurred—to nine other states, some as far-flung as North Carolina, Michigan, and Idaho.

Enlarge / Bayes factors for inferred movement between different discrete traits of H5N1 clade 2.3.4.4b viruses demonstrating the frequency of movement.

Putative transmission pathways of HPAI H5N1 clade 2.3.4.4b genotype B3.13 supported by epidemiological links, animal movements, and genomic analysis. [/ars_img]The bad news is that those lines connecting the herds aren’t solid. There are gaps in which the genetic data suggests unidentified transmission occurred, maybe in unsampled cows, maybe in other animals entirely. The genetic data is clear that once this strain of bird flu—H5N1 clade 2.3.4.4 genotype B3.13 —hopped into cattle, it could readily spread to other mammals. The genetic data links viruses from cattle moving many times into other animals: There were five cattle-to-poultry jumps, one cattle-to-raccoon transmission, two events where the virus moved from cattle to domestic cats, and three times when the virus from cattle spilled back into wild birds.

“We cannot exclude the possibility that this genotype is circulating in unsampled locations and hosts as the existing analysis suggests that data are missing and undersurveillance may obscure transmission inferred using phylogenetic methods,” the USDA researchers wrote in their preprint.

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