Dozens of people with glaucoma-like symptoms have tested positive for a virus that we thought affected only marine life
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A virus typically found in marine life has been linked to glaucoma-like symptoms and irreversible vision loss in a small group of people in China. This marks the first instance of a virus from aquatic animals affecting human health. The infections appear to have arisen from consuming raw seafood and handling aquatic creatures, with indications of possible human-to-human transmission.
“That this virus can infect invertebrates, fish, and mammals is pretty remarkable,” says Edward Holmes from the University of Sydney, Australia. “I can’t think of a virus with such a broad host range.”
In China, there has been a rise in cases of a condition called persistent ocular hypertension viral anterior uveitis (POH-VAU), characterized by eye inflammation and high pressure, akin to glaucoma. This damages the optic nerve and may lead to vision loss.
To investigate the cause of the increased cases, a research team, including experts from the Chinese Academy of Fishery Sciences in Qingdao, studied 70 individuals diagnosed with the condition between January 2022 and April 2025.
All 70 were tested for covert mortality nodavirus, a virus affecting various marine animals, and all results were positive. “To date, no virus originating from aquatic animals has been shown to infect humans and directly cause disease,” the researchers state. Patients received medication to reduce swelling, but around one-third required surgery, and one individual suffered irreversible vision loss.
To explore the virus further, researchers infected mice, which developed significant pathological changes in the cornea, iris, and retina within a month. They also observed that mice sharing water transmitted the virus to each other.
Of the 70 studied, more than half were home-based handlers of aquatic animals, potentially explaining their infections. Additionally, about 16 percent were either consumers of raw aquatic products or had close contact with high-risk groups.
Although there is no direct evidence of human-to-human transmission, an epidemiological study identified a “distinct subgroup of urban patients with POH-VAU” who had no contact with aquatic animals or other risk factors, apart from close contact with family members. These relatives, at high risk of contracting covert mortality nodavirus, had hand injuries when handling aquatic animals. This suggests the virus might spread within families, potentially through shared utensils, according to the researchers.
To assess the virus’s prevalence, researchers analyzed 523 farmed and wild aquatic animals from Asia, North and South America, Europe, Antarctica, and Africa. They found covert mortality nodavirus globally in 49 species, including prawns, crabs, fish, sea cucumbers, and barnacles. These animals exhibited symptoms like lethargy and loss of color, though the reason it affects human eyes remains unclear.
Holmes suggests the pathogen may be more widespread than currently known. “I think it’s very likely that the virus will be present in other species that we’ve not yet sampled,” he says. “I don’t think it can be totally excluded that it passed through another species first, perhaps even another mammal.”
The virus might also be circulating among marine life that consumes infected animals. For example, farmed shrimp often eat frozen brine shrimp or Antarctic krill, which can lead to infection. Warmer water exacerbates the infection in sea life, indicating that Antarctic species could serve as a reservoir for the pathogen, even if they remain asymptomatic.
Researchers warn that the transmission of covert mortality nodavirus from marine animals to humans poses a new biosecurity threat. However, Holmes emphasizes the lack of clear evidence for human-to-human transmission, stating, “It’s not an epidemic.”
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