Animals traded through global wildlife markets are far more likely to carry diseases that can infect humans, and the risk grows the longer those species remain in circulation, according to a new study.

The analysis, published Thursday in Science, examined decades of global wildlife trade data and found that 41% of traded mammal species share at least one pathogen with humans, compared with just 6.4% of species not involved in trade.

The researchers also found that the number of pathogens shared between animals and humans increases over time. On average, a species acquires one additional human-infecting pathogen for every decade it is present in the global wildlife trade.

The findings suggest that wildlife trade does not simply expose humans to existing disease risks, but may actively amplify them over time.

“Our study is the strongest evidence to date that reducing wildlife trade will reduce pandemic risk,” said Colin Carlson, an epidemiologist at the Yale School of Public Health and a co-author of the study.

Scientists have already long linked wildlife trade to specific outbreaks such as HIV, Ebola and COVID-19. The new research, which draws on 40 years of global trade records and pathogen data, attempts to measure the relationship on a larger scale.

The results point to a broader pattern. Repeated and prolonged contact between humans and wild animals creates more opportunities for pathogens to move between species.

“What stands out most is how clearly the findings reinforce something many of us in disease ecology have been concerned about for years: it’s not just the presence of wildlife trade, but the intensity and duration of contact that elevates risk,” said Thomas Gillespie, a professor of environmental sciences and environmental health at Emory University, who was not involved in the study.

Wildlife trade, as defined in this study, includes a wide range of activities, from hunting and breeding to transport, storage and sale. At each stage, animals are handled, confined and often brought into close proximity with both humans and other animal species. These conditions can facilitate the spread of viruses, bacteria and parasites.

Over time, those repeated interactions create more opportunities for pathogens to circulate, adapt and potentially spill over into human populations.

Carlson said one of the most striking findings was how strongly time in trade predicted pathogen sharing.

“That time-in-trade effect is the smoking gun,” he said. “We wouldn’t see that unless pathogens were jumping from animals to humans.”

He added that the findings suggest wildlife trade should be considered one of the major drivers of disease emergence, alongside deforestation, agriculture and climate change.

The study also found that certain forms of trade may carry higher risks. Species sold in live-animal markets were more likely to share pathogens with humans than those sold as meat or animal products. Illegally traded species also were more likely to be the cause of disease, though researchers emphasized that risk is not limited to illicit markets.

“Focusing on illegal wildlife trade is not enough,” said Meredith Gore, a conservation criminologist at the University of Maryland and a co-author of the study. “Pathogen transmission is a consequence of general and diverse uses of wildlife by people. This includes illegal and legal trade.”

Most international frameworks governing wildlife trade, including the Convention on International Trade in Endangered Species of Wild Fauna and Flora, or CITES, were designed primarily to protect species from overexploitation, according to Gore.

“There are clear and currently unmet opportunities for more directly including zoonotic disease risk consideration into current regulations,” Gore said.

In particular, the global nature of the trade complicates efforts to manage risk.

“Animals and pathogens do not care about political borders,” said Jérôme Gippet, a biologist at the University of Fribourg and the University of Lausanne in Switzerland and the study’s lead author. “Without globally coordinated efforts, I do not see how we can limit these risks efficiently.”

The researchers say their findings underscore the need for a more coordinated approach that bridges conservation, public health and trade policy and treats wildlife trade as a central driver of global health risk. The study’s findings also highlight gaps in disease surveillance systems, which often fail to detect pathogens circulating in wildlife before they reach humans.

“Risk is accumulating in a way that current surveillance isn’t capturing,” said Evan Eskew, a disease ecologist at the University of Idaho and a co-author of the study.

Few countries, he said, systematically track which species are being traded across their borders, and even fewer conduct routine pathogen screening in those animals. As a result, potential threats can go undetected until they spill over into human populations.

Eskew said expanding surveillance, particularly for species already known to carry zoonotic pathogens, could help identify risks earlier and prevent outbreaks from spreading.

“We need to be looking for the next pandemic virus on fur farms, in hunting communities, and even at border checkpoints where wildlife are imported,” Carlson said. “Right now, we’re flying blind, especially in places where we’ve criminalized wildlife trade and driven it underground.”

NASA’s 10-day Artemis II mission to fly around the moon safely splashed down off the San Diego coast Friday, marking the end of humanity’s first flight to the moon in over 50 years.

The new NASA administrator, born over a decade after the last Apollo mission, immediately made it clear he intends the gap between Artemis II and the agency’s next moon mission to be much, much shorter.

“You hear sometimes around here, ‘this is a once in a lifetime’ — no its not,” NASA Administrator Jared Isaacman said aboard a recovery vessel out in the Pacific, moments after the crew splashed down. “This is just the beginning, we are going to get back into doing on this with frequency, sending missions to the moon until we land on it in 2028 and start building our base.”

Here’s how the U.S. space agency hopes to do it.

NASA’s vision for the moon

A week before Artemis II launched, NASA outlined its ambitious new plan for creating a sustained presence on the moon, which can serve as a testing ground for eventual missions to Mars.

Most notably, the agency scrapped long-standing plans to build a space station orbiting the moon, called Gateway. Instead, it would focus on building a base on the lunar surface.

“I think we’d rather be on the surface where a lot of the learning’s going to take place, where we can … build the skills, test the technology, the capabilities we’re going to need some day if we actually go to Mars and want to bring our astronauts home to talk about it,” Isaacman said in an interview with the publication NASASpaceflight.

“It’s not like you’re just going to be on Gateway looking down,” he added. “You’re going to probably be looking down on another country’s astronauts.”

The space agency’s Artemis program is designed to make the moon base vision a reality.

The next Artemis missions

The next Artemis mission is slated for 2027. Artemis III will stick in near-Earth orbit — closer to where the International Space Station sits as opposed to traveling into deep space like Artemis II.

Around Earth, the agency plans to test docking procedures between its Orion spacecraft and the lunar landers that will carry astronauts from the moon’s orbit down to its surface. To build these landers, it tapped the private space companies Blue Origin, founded by Jeff Bezos, and SpaceX, founded by Elon Musk.

Then, in early 2028, it intends to launch Artemis IV. The Orion spacecraft will carry astronauts to the moon’s orbit, and a lunar lander will take two of them down to the moon’s south pole, where they will spend a week conducting science.

Artemis V and beyond will aim to accelerate the cadence of lunar landings to one every six months and continue to test technology to make lunar landings easier and cheaper.

Lessons from Artemis II

Artemis II focused on putting the Orion spacecraft through its paces — primarily by testing its life support systems and piloting the spacecraft for the first time. For example, the crew dealt with multiple issues with their space toilet.

NASA also used the mission as an opportunity to study Orion’s troubled heat shield, which unexpectedly chipped in more than 100 spots on the uncrewed Artemis I test mission in 2022. By using a new reentry trajectory, Isaacman said that “no unexpected conditions were observed” in initial assessments.

However, the Orion spacecraft experienced issues with helium valves on Orion’s propulsion system, which helps the crew navigate in space. Ahead of launch, NASA noticed helium leaking in the system but determined, since Artemis II has a much simpler trajectory than future missions, the leaking wouldn’t significantly affect the mission.

In space, the leaking worsened, ultimately convincing NASA it would have to redesign the system for future missions.

Beyond the technical objectives of Artemis II, NASA officials were particularly pleased with the public response to the mission and the astronauts’ ability to connect with the public.

The lunar flyby is already NASA’s most viewed live broadcast on YouTube with more than 27 million views. Artemis II’s launch and splashdown are also within the top five most viewed broadcasts.

In space, the astronauts spoke eloquently of the surreal sights of the moon and their deep love for our home planet.

“I would suggest to you that when you look up here, you’re not looking at us,” said Canadian Space Agency astronaut and Artemis II mission specialist astronaut Jeremy Hansen, back in Houston Saturday. “We are a mirror reflecting you. And if you like what you see, then just look a little deeper. This is you.”

The hurdles to Artemis III

NASA is already building its next high-power rocket to launch the Artemis III Orion spacecraft. The agency plans to ship the massive orange core stage for the rocket from New Orleans to Florida this month. The Orion spacecraft’s main two sections are already at NASA’s Kennedy Space Center along the Florida coast.

A redesigned heat shield, aimed at addressing the root cause of the unexpected damage during Artemis I, is already built. However, the agency is not yet sure whether it will be able to fix the faulty Orion propulsion system, built in Germany by the European Space Agency, in Florida or if NASA will have to ship it back across the Atlantic.

And neither SpaceX nor Blue Origin have tested their landers in space yet. A NASA audit last month found that “both SpaceX and Blue Origin have experienced schedule delays and face technical and integration challenges that have the potential to further impact lander costs and delivery schedules.”

Yet, NASA remains steadfast on its 2027 launch timeline. The agency promised to announce the Artemis III crew “soon.”