Virus from marine animals is causing weird eye problems in people
Dozens of people with glaucoma-like symptoms tested positive for a virus that we thought only affected marine life.
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A virus that usually affects marine animals has caused glaucoma-like symptoms and even irreversible vision loss in a small but growing group of people in China. This is the first time that a virus from aquatic animals has infected people and caused health problems. These cases are thought to have developed after eating raw seafood and handling aquatic animals, but there is also evidence of human-to-human transmission.
“The fact that this virus can infect invertebrates, fish and mammals is quite remarkable,” says Edward Holmes of the University of Sydney, Australia. “I can’t think of a virus with such a wide host range.”
Cases of a condition called persistent ocular hypertension viral anterior uveitis (POH-VAU) are increasing in China, with no clear cause. It is defined as inflammation and high pressure in the eye, similar to glaucoma, that damages the optic nerve and can lead to vision loss.
To understand why cases are increasing, a team of researchers – including scientists from the Chinese Academy of Fisheries Sciences in Qingdao – recruited 70 people in China who were diagnosed with the disease between January 2022 and April 2025.
They tested this cohort for covert mortality nodavirus, which infects a range of marine animals – all 70 tests came back positive. “So far, no viruses from aquatic animals have been shown to infect humans and directly cause disease,” say the researchers, who declined to be interviewed. The individuals were given medication to relieve the swelling, but about a third still required surgery and one person developed irreversible vision loss.
To better understand the virus, researchers infected mice, which developed “obvious pathological changes in the cornea, iris and retina” within a month. They also noticed that mice sharing water were able to transmit the virus to each other.
Of the 70 people studied by the researchers, more than half were handlers of aquatic animals at home, which could be the source of their infections. But the team also reported that about 16% of them were either consumers of raw aquatic products or close contact with high-risk groups.
There is no direct evidence of human-to-human infection. However, when researchers conducted an epidemiological study, they discovered a “distinct subgroup of urban POH-VAU patients” who had no contact with aquatic animals or other risk factors aside from close contact with family members. These relatives are at high risk of contracting a secret-lethal nodavirus and may have suffered hand injuries when handling aquatic animals. This suggests that the virus could spread within families, for example through sharing utensils, researchers say.
To understand the extent of the virus, researchers analyzed 523 farmed and wild aquatic animals collected in Asia, North and South America, Europe, Antarctica and Africa. They concluded that covert mortality nodavirus is present globally. The team also found it was present in 49 species – including shrimp, crabs, fish, sea cucumbers and barnacles – where it causes symptoms such as lethargy and loss of color. It is unclear why this affects human eyes.
Holmes adds that it’s plausible that the pathogen is more widespread than we think. “I think it’s very likely that the virus is present in other species that we haven’t sampled yet,” he says. “I don’t think it can be completely ruled out that it first crossed into another species, perhaps even another mammal.”
The virus can also spread among marine life that feeds on infected animals. For example, farmed shrimp are often fed frozen brine shrimp or Antarctic krill, and researchers have found that this can lead to infection. The introduction of the virus into warmer waters has also made marine life more infected, suggesting that Antarctic species could act as a reservoir for the pathogen, even if they don’t get sick themselves.
Researchers say this spread of the covert-killing nodavirus from marine animals to humans poses a new biosecurity risk. However, Holmes says there is no clear evidence of human-to-human transmission. “It’s not an epidemic,” he said.
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