Marine Virus Jumps to Humans Causing Permanent Eye Damage

Researchers have identified a marine virus that has crossed from aquatic animals into humans for the first time, causing a serious inflammatory eye condition. The pathogen, known as covert mortality nodavirus (CMNV), is linked to a syndrome characterized by high internal eye pressure and inflammation that can lead to permanent vision loss.

The findings were published in Nature Microbiology and detail the discovery of the virus in the ocular tissues of patients diagnosed with persistent ocular hypertensive viral anterior uveitis, or POH-VAU. This represents the first reported association between an aquatic pathogen of this nature and human disease.

Understanding Covert Mortality Nodavirus

CMNV is a small RNA virus that has long circulated among marine life, specifically within farmed shrimp and various fish species. It earned its name from its behavior in shrimp populations, where it causes mortality without obvious external signs, making outbreaks difficult to detect until significant losses have already occurred.

Before the discovery of human infections, scientists had documented the virus’s ability to infect a wide range of hosts. Research showed that CMNV naturally infects the goby species Mugilogobius abei, causing retinal lesions and damage to eye-related tissues. Experimental models using zebrafish also demonstrated that the virus produces retinal and ocular pathology in vertebrates.

Impact on Human Health

In humans, the infection manifests as POH-VAU, a condition defined by inflammation and high pressure within the eye. These symptoms are similar to glaucoma, as the increased pressure damages the optic nerve, which can result in the loss of vision.

A study conducted by researchers, including scientists from the Chinese Academy of Fishery Sciences in Qingdao, examined a cohort of 70 people in China who were diagnosed with the condition between January 2022 and April 2025. All 70 individuals in this group tested positive for the covert mortality nodavirus.

While patients were administered medication to reduce swelling, the severity of the condition varied. Approximately one-third of the patients required surgical intervention and one individual suffered irreversible vision loss.

Transmission and Host Range

The exact mechanism of how the virus jumped to humans is still being studied, but current evidence suggests two primary routes of exposure. Cases are thought to have developed after individuals handled aquatic animals or consumed raw seafood.

Beyond initial animal-to-human transmission, there are also signs that human-to-human transmission may be occurring. This broad ability to infect different species has drawn attention from the scientific community.

That this virus can infect invertebrates, fish and mammals is pretty remarkable. I can’t think of a virus with such a broad host range.

Edward Holmes, University of Sydney

Public Health Implications

The emergence of CMNV in humans raises new questions regarding the potential for other marine viruses to cross into human populations. Because the virus replicates quickly and adapts well to new hosts in aquatic environments, its jump to mammals is a significant biological development.

Until this discovery, no virus originating from aquatic animals had been shown to infect humans and directly cause disease. The identification of CMNV as the cause of POH-VAU provides a clear etiology for a condition that had previously seen increasing cases in China without a known cause.