That magical swim with dolphins in Hawaii may not be as harmless as it looks. University of Hawaii scientists have confirmed, for the first time, that dolphins here are carrying a bacterial infection that can be transmitted to people.
While cases of humans catching it from marine mammals are rare, the discovery is enough to rattle assumptions about what has long been sold as a safe, once-in-a-lifetime encounter in Hawaii’s waters.
Dolphin disease discovery rattles Hawaii safety assumptions.
Three striped dolphins stranded on East Oahu in June tested positive for Brucella ceti, a form of brucellosis. For dolphins, the infection has been linked to brain inflammation, reproductive failure, and even death. For individuals, it can manifest as recurring fevers, sweats, arthritis, and occasionally neurological damage if left untreated.
Kristi West, director of UH’s Health and Stranding Lab, said the strandings likely hint at something bigger. “The rapid succession of strandings likely represents many more dolphins that died and were lost at sea,” she said. “These animals serve as sentinels for the health of Hawaii’s marine environment, and their condition reflects wider risks.”
A peer-reviewed study published this year found that nearly one-third of Hawaii’s stranded cetaceans tested positive for Brucella ceti between 2000 and 2024. All of the striped dolphins studied carried the infection.
Researchers note that this is not unique to Hawaii, as the disease has been documented elsewhere; however, the local discovery highlights the limited understanding of what visitors may be swimming alongside.
Brucella ceti is a hidden risk in Hawaii’s waters.
Brucellosis is a “zoonotic” disease, meaning it can move from animals to people. Globally, most human cases originate from livestock, but marine strains, such as Brucella ceti, have been detected in dolphins, porpoises, and whales.
Actual human infections from dolphins and whales are rare, but they’ve been documented after close contact with stranded or sick animals, enough for scientists to say the risk should not be ignored.
West has urged the public not to take chances. “Brucella ceti can be dangerous to humans who touch infected marine mammals,” she said, stressing that anyone who finds a stranded animal should call NOAA instead of trying to push it back to sea.
NOAA added that while the danger to people is considered low, following the rules, maintaining distance, and calling the hotline are essential to keeping both visitors and dolphins safe.
Dolphin tours: magical moments with possible hidden risks.
Picture yourself snorkeling off West Oahu when a pod of dolphins swims past, so close you could virtually reach out and touch them. For many visitors, that’s the story they take home. Yet the same closeness that feels like magic may also carry risk. Scientists say that even a small cut, with seawater splashing in, could be enough to cause an infection.
Rules say boats and swimmers must stay 50 yards back, but in Hawaii’s open ocean, who can measure? With few patrols and dolphins often closing the gap on their own, the line between safe and unsafe is blurred almost instantly.
Hawaii wildlife encounters: a mix of wonder and risk.
Hawaii’s wildlife has always carried hidden risks. Snorkeling has been linked with shallow-water blackout. Manta ray dives off the Big Island face battles over crowding and permits. Sea turtles and monk seals have become flashpoints, sometimes ending in fines and angry headlines when visitors push too close. Dolphins now join that list, with a danger visitors can’t see and may not even realize is present.
Experts say the risk is low and manageable if visitors modify their approach to Hawaii’s marine life. That means keeping a safe distance, resisting the urge to push stranded animals back to sea, and picking up the phone to report what you see instead of rushing in. Those choices protect both people and the animals themselves.
How dolphin disease could impact Hawaii tourism.
Dolphin tours are a multimillion-dollar business in Hawaii, especially in West Oahu and along the Kona Coast. They support small operators, local guides, and countless jobs tied to the visitor economy. But the perception of risk, even if small, could have a significant impact.
Some operators emphasize that their practices already prioritize safety and maintain respectful distance from wildlife. Still, once guests are in the water, not everyone follows instructions, and dolphins themselves sometimes close the gap. That reality makes the encounters difficult to control 100%.
If visitors begin to see dolphin swims as unsafe, cancellations could ripple through the industry. At the same time, the discovery could encourage Hawaii to adopt more sustainable and less invasive wildlife encounters, which many travelers increasingly desire.
Will Hawaii tighten its rules on dolphin encounters?
Hawaii hasn’t announced new restrictions yet, but other countries have already done so. New Zealand has curbed dolphin swim tours to protect pods and reduce risk. Some destinations have banned them outright. Whether Hawaii goes down that road will depend on how state and federal officials weigh the science against the economic benefits of tourism.
At the same time, a pending court case is testing the limits of these tours in Hawaii and whether stricter enforcement is forthcoming. We covered that in detail here.
For now, rules discourage close approaches, but enforcement across Hawaii’s vast ocean is limited. With the new UH findings, pressure may build for Hawaii to act sooner rather than later.
Hawaii’s waters remain among the most remarkable places to swim, and that has not changed. What this discovery does remind us is that the ocean here is wild, unpredictable, and not a theme park.
What happens next is up to visitors, tour operators, and policymakers, and the choices they make now will shape both the future of dolphin tourism and the safety of those who come here.
What do you think? Should Hawaii tighten its rules on dolphin encounters in light of this new research, or are the risks being overstated? Have you ever joined a dolphin swim tour, and would this discovery change your plans? Share your thoughts, please.
Image courtesy NOAA.
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