Fans of "The Walking Dead" know it doesn't take much to start a species-ending apocalypse.
A bite. A scratch. A sneeze. One opportunity to pass a pathogen to someone else and the race toward extinction begins.
That fictional scenario is scary enough, but for some species the reality is even more terrifying—and more likely to happen sometime in the not-so-distant future.
Take the Hawaiian monk seal. Once hunted into near-extinction for their meat and fur in the 19th century, only a few hundred monk seals remained when they were finally protected under the Endangered Species Act in 1976. Intense conservation efforts increased that population to about 1,500 in the 1980s, but the seals still face a precarious recovery. The animals frequently die from entanglement with fishing gear and their population has shrunk to about 1,100 today.
The seals still carry scars from that close call with extinction. The species has the lowest genetic diversity of any of the world's seal species, which means they have a similarly low resistance to disease. The introduction of a virus to the ecosystem could easily wipe out the species, said Charles Littnan, lead scientist for the National Oceanic and Atmospheric Administration's Hawaiian Monk Seal Research Program.
"The destructive force of a disease is comparable to nothing"
This is not a theoretical danger.
Around the world, seals and other marine species have experienced several mass die-offs after exposure to morbilliviruses, a group of diseases that include canine distemper and the measles.
"The destructive force of a disease is comparable to nothing," Littnan said. "There is no reason to believe that if morbillivirus comes and gets into monk seals, and this program isn't in place, that it will be anything less than catastrophic."
In 1988, more than 18,000 harbor seals died in Europe after they became infected with what was later identified as phocine distemper, a virus that specifically affects seals. Another outbreak in 2000 killed more than 21,000 harbor seals in the North Sea. Several outbreaks of canine distemper over the years have also killed tens of thousands of Baikal seals, Caspian seals and crabeater seals.
Morbilliviruses are not naturally found in Hawaii. The seals, Littnan said, have never been exposed to them. But what would happen if one of the diseases arrived—via a dog or some other carrier—and the seals became infected?
NOAA scientists have spent years exploring that question. Vaccines have been tested, although they won't be administered unless there's an emergency because the vaccines contain live versions of the viruses. Meanwhile, risk assessment models have been run to try to understand how the diseases might spread if they arrive. The team has spent the last few years preparing an emergency response plan just in case morbillivirus appeared.
Last month they put that plan to the test. A team of researchers, staff and volunteers fanned out across Oahu and the smaller Northwestern Hawaiian Islands to conduct a vaccination drill that would let them know how well they had prepared.
It was grueling work. "They were incredibly long days," said Littnan, who coordinated the drill. "The effort these teams put in just blew me away." Teams fought wind, sun and rain as they fanned out by truck and boat to try to find every monk seal they could—no small task since the large animals live mostly solitary lives and often perch on fairly precarious positions on the island's rocky beaches.
If this had been a real outbreak situation, each member of the team would have been armed with a four-foot pole tipped with a vaccine-filled syringe. As it was, the team did not actually approach the seals. They did, however, use the drill to test their models and disaster planning.
"I was back at the command center throwing out scenarios and challenging our veterinarians and other teams to think about their decision process in various scenarios," Littnan explained. What if they encountered a sick animal? What if a seal was in a place they couldn't reach? What if—as really became the case—one of their vehicles broke down and they needed a backup?
Then there was perhaps the most important question that they explored during the drill: What if someone made a mistake with quarantine protocols and their rescue facilities became infected?
In the drill, just like in a zombie apocalypse, all it took was a few drops of blood.
"That drove it home to everybody," Littnan said. It's an important lesson, since the program regularly encounters seals that have been wounded by fishing equipment and brings them in for surgery. "Any animal we bring in could be infected with morbillivirus or something similar. If we're not aware of it at the time, it could threaten all of the animals we work with."
Over the course of two days, the team "vaccinated" about half of the seals on Oahu. (During a real event, they would have aimed for 90 percent, and then repeated the whole thing again a few weeks later to provide booster shots.)
The drill, although effective, revealed some flaws in their plan. "We had pretty dramatically underestimated the amount of backup resources that we would need just to maintain the operation should any small thing go wrong," Littnan said.
They learned from the lesson. The drill, he said, allowed them to improve their plan "leaps and bounds" above what they previously believed was a robust approach. "We feel a lot better now from the lessons and are much more confident going into a real vaccination attempt if this were to happen tomorrow," Littnan added.
And tomorrow is an all-too-likely possibility.
When NOAA started working on its vaccination plan in 2005, marine-bound morbillivirus in Hawaii was just a theoretical problem. That's no longer the case. In 2010, a Longman's beaked whale infected with morbillivirus washed up on Maui, the first time morbillivirus had been found in a marine mammal from the central Pacific.
Two years later, a juvenile northern fur seal from the west coast of the US also turned up in Hawaii, the first time the species had been seen in the islands. Although it was not infected with morbillivirus, Littnan explained that other northern fur seals do appear to carry the disease. It's still unknown what inspired the young seal to swim thousands of miles across the Pacific.
Then there's the potential risk from dogs. Canine distemper is relatively rare in Hawaii, but the state relaxed its quarantine rules in 2003, which creates a bit more risk. People often walk their dogs on the same beaches where monk seals sun themselves. Last year one monk seal pup died and four others were injured after a dog attack on Kauai.
Infection wouldn't even require an attack. Littnan says a dog sneezing near a seal might be enough to start an epidemic.
Littnan says they must plan as if any disease that strikes Hawaiian monk seals would be fatal. "There are not a lot of good stories about morbillivirus in other marine mammals," he said. Since Hawaiian monk seals have no natural immunity to these diseases, their arrival could, indeed, look like something out of "The Walking Dead."
Hell or Salt Water is a series on Motherboard about exploring and preserving our oceans. Follow along here.