A cynomolgus monkey sits in a tree near Danville, Pennsylvania,...

A cynomolgus monkey sits in a tree near Danville, Pennsylvania, on Jan. 22. A truck carrying 100 monkeys to a laboratory crashed allowing four of them to escape, triggering a search by police who warned the public not to approach the animals. Three were later captured, but one was still on the loose on the morning of Jan. 22. Credit: Pennsylvania State Police Department/Stefani Reynolds

The escape of three monkeys from their cages after a crash in central Pennsylvania did more than alarm local residents — it shone a sliver of light into a dark underworld of animal experimentation that normally rumbles through state after state, undetected. It’s something we need to talk about — and end.

Animal experimentation is a dangerous, ugly business, wrought with disease and violence. As the traffic incident in Danville, Pennsylvania, shows, it’s also an industry that casts a wide net that touches quiet little hamlets throughout the U.S. with regularity, exposing residents to unknown dangers tucked inside unmarked trailers. In the past decades, imported monkeys have brought with them multiple strains of Ebola, tuberculosis, measles, simian hemorrhagic fever, herpes B, malaria and other nasty diseases. According to the Centers for Disease Control and Prevention (CDC), some are dead on arrival and many more die within the first month of quarantine.

In 2020, more than 26,000 monkeys distributed across 115 shipments arrived in the U.S. The vast majority of monkeys like these are destined for private pharmaceutical laboratories, where they will be killed in about six months. Others go to university laboratories, including the seven federally funded national primate research centers, where they will be used for years — sometimes decades — in experiment after experiment.

The 100 monkeys on the truck that crashed on I-80 had just arrived from Mauritius, a tiny island in the Indian Ocean east of Madagascar, some 9,400 miles away. They were not quarantined but just plucked from their homes or pulled from a breeding facility, shoved three to a crate and packed into a trailer that ultimately crashed, potentially exposing the residents of Danville to a raft of diseases that no one knew they had.

To say that authorities were concerned about this possibility is an understatement. The Pennsylvania State Police warned residents "not to approach, attempt to catch, or come in contact with the [last missing] monkey. Please call 911 immediately."

There was good reason for caution. One woman who came face to face with the monkeys got an eyeful of saliva when one of them hissed at her. She began a course of rabies-prevention medication and was started on antivirals after her eye became red and weepy. The next day, she developed a cough and runny nose.

It sounds like the plot to a dozen movies: A diseased monkey escapes and infects a human, sparking a pandemic. But it’s not so far-fetched. In November 1989, dozens of imported long-tailed macaques were sent to a laboratory in Reston, Virginia, and with them they brought a never-before-seen strain of Ebola. Four humans got sick. All the monkeys were killed. The CDC discovered in December 1989 that long-tailed macaques who had been recently imported into a facility in Philadelphia were infected with a variant of this Ebola Reston virus, which they named RESTV/Pen. A few years later, Ebola Reston was brought into the U.S. again, this time to Texas, by another monkey.

The problem with the Danville crash is not the crash in Danville. It’s the dozens of trucks and trailers ambling through small-town America, filled with undocumented monkeys who were taken from far-flung regions of the globe and carry unknown diseases. That’s what it means when officials such as Dr. Anthony Fauci call for more animal experimentation. It means more trucks in more towns with more monkeys, potentially more diseases and definitely increased danger.

Danville dodged a bullet last week. But as long as there is monkey experimentation, there will be more loaded guns crisscrossing small towns everywhere. Avoiding the danger, however, is simple: Invest in human-relevant research methods instead of monkeys.

In vitro work using human cells, integrative modeling and molecular simulations or three-dimensional printed human tissues, cell-based assays and organs-on-a-chip — all these offer far more promise than animal experimentation ever could, and we can leave the monkeys where they are.