A previously unknown virus originating from marine animals is causing a surge in glaucoma-like symptoms and, in some cases, irreversible vision loss among people in China. This marks the first documented instance of a disease-causing spillover from aquatic animals to humans, raising concerns about global biosecurity risks.
The Emergence of POH-VAU
Cases of persistent ocular hypertension viral anterior uveitis (POH-VAU) – a condition mimicking glaucoma – have been increasing in China since early 2022. The illness involves inflammation and elevated pressure within the eye, potentially leading to optic nerve damage and permanent vision impairment. Researchers investigating the outbreak tested 70 diagnosed patients and found that all were infected with covert mortality nodavirus, a pathogen typically found in fish, crustaceans, and other marine life.
Transmission Pathways and Host Range
The most likely route of infection appears to be consumption of raw seafood or direct contact with aquatic animals. Over half of the studied patients worked directly with marine species, while 16% were consumers of raw aquatic products. However, the virus also demonstrates an unusually broad host range, infecting invertebrates, fish, and mammals alike. More alarmingly, epidemiological data suggests human-to-human transmission is possible. A subgroup of urban patients showed no prior contact with aquatic animals but contracted the virus through close family members, some of whom had hand injuries during handling of infected seafood.
Global Prevalence and Viral Spread
Researchers analyzed over 500 aquatic animals from around the world, including farmed and wild species from Asia, the Americas, Europe, and Antarctica. Covert mortality nodavirus was present in 49 species, causing lethargy and discoloration in marine life. The virus can also spread through contaminated food chains: farmed shrimp often consume infected brine shrimp or krill, exacerbating the problem. Warming water temperatures seem to increase viral replication in some species, potentially allowing Antarctic animals to act as asymptomatic reservoirs.
Why This Matters
This outbreak is significant for several reasons. First, it demonstrates how easily zoonotic viruses can jump species and cause unexpected human disease. Second, the virus’s broad host range suggests it could spread further than initially believed. Third, the potential for human-to-human transmission raises the risk of localized outbreaks if not contained. Experts caution against panic, as this is not yet an epidemic, but stress the need for increased biosecurity measures in aquaculture and seafood processing.
“This pathogen is more prevalent than we think,” says Edward Holmes of the University of Sydney. “It’s very likely the virus is present in other species we haven’t sampled yet.”
The study underscores the importance of global surveillance, rapid response protocols, and public health education to prevent future zoonotic spillover events.
