The World Health Organization has issued an ominous warning about bird flu. In a Wednesday press briefing, the international agency’s director-general, Tedros Adhanom Ghebreyesus, noted that the disease’s current trajectory leaves humans worryingly exposed.
Over the past year, avian influenza has gone viral, worldwide—obviously in a bad way. Outbreak after outbreak of a particularly dangerous strain of H5N1 bird flu has popped up in both wild and domestic birds on every continent aside from Antarctica (and scientists are becoming increasingly worried about the penguins there too.) Now, even mammals appear to be falling victim to the disease.
“H5N1 has spread widely in wild birds and poultry for 25 years, but the recent spillover to mammals needs to be monitored closely,” WHO’s Ghebreysus said. “Since H5N1 first emerged in 1996 we have only seen rare and non-sustained transmission of H5N1 to and between humans. But we cannot assume that will remain the case, and we must prepare for any change in the status quo,” he added.
Usually, H5N1 only spreads between birds. But in this ongoing series of outbreaks, something unsettling has started to happen. Mammals are getting sick too. In test results announced last month, three grizzly bears in Montana tested positive for bird flu. Similar cases have been noted among otters and foxes in the United Kingdom. Earlier this week, Peruvian officials confirmed that they’d detected the viral strain among multiple sea lions and at least one dolphin in the South American country.
Most disconcertingly: in an outbreak among minks on a Spanish fur farm, H5N1 appeared to spread from weasel to weasel. In other instances of mammalian infection, the assumption is that mammals pick up avian influenza through direct contact with wild, infected birds. With the (now culled) minks though, science suggests that wasn’t the case.
A report about the incident published in October 2022 concluded that the number of infected animals and the way the spread occurred “indicate that an onward transmission of the virus to other minks may have taken place.” The report researchers also noted that the viral strain found among the farmed weasels carried mutations, some of which could potentially make the disease more transmissible between a wider array of species—though more conclusive studies on this are ongoing.
Minks have very similar respiratory tracts to humans. Among animals, they’re considered a likely vector point for new and emerging diseases. Already, we’ve seen this play out with covid-19. One 2021 study concluded that that the weasels could be a “highly susceptible host species,” of avian influenza, specifically.
In the past year, there’s been one documented case of the virus infecting a person in the U.S., along with at least one case in China. In total, the current spreading H5N1 variant has led to fewer than 10 known cases in people since December 2021. Further, there’s been no evidence of any human-to-human transmission in this current set of outbreaks, according to WHO and the Centers for Disease Control. Though human-to-human transmission is possible, the phenomenon has rarely occurred since the disease first emerged in people in 2003. H5N1 has never before been documented passing among humans in any sustained way.
For those reasons, Ghebreyesus qualified his remarks and noted that “For the moment, WHO assesses the risk to humans as low.” But without enough attention and action—there’s no guarantee things stay that way.
WHO says it is working with international governments to carefully keep tabs on the situation. And the agency recommends that countries boost their individual surveillance programs—particularly where humans and animals commonly interact.
The agency also had a warning for individuals. “As always, people are advised not to touch or collect dead or sick wild animals, but to report them to the local authorities,” Ghebreyesus said. If you want to avoid becoming patient zero for the next global pandemic, Gizmodo suggests you follow that advice.