Until recently, a virus called covert mortality nodavirus, or CMNV, was mostly a problem for shrimp farmers. It was first found in fish farms in China in 2014. The virus caused shrimp to die without clear warning signs. Many would sink to the bottom of ponds, so farmers often did not realize what was happening. Over time, the virus spread through the global seafood supply and began infecting many types of marine life, including fish and shellfish. In some cases, up to 80 percent of shrimp were lost.
For years, experts believed CMNV could not infect humans. Even in 2024, health groups reported no risk to people. However, new research has changed that view. A recent study found that CMNV may be linked to a newly identified eye disease called persistent ocular hypertensive viral anterior uveitis, or POH-VAU.
This eye condition is serious and can be difficult to treat. It causes inflammation inside the eye, along with small deposits on the inner layer of the cornea. The colored part of the eye, called the iris, can become damaged, and eye pressure may rise to unsafe levels. These problems often recur and may not respond to standard treatments. About one out of three patients in the study needed surgery to lower eye pressure, and one patient experienced permanent vision loss.
Most patients were between 45 and 70 years old. A major risk factor was close contact with seafood or aquatic animals. Many patients handled raw seafood at home without gloves, while others ate raw or undercooked seafood. Direct contact appears to be the primary route of exposure. A smaller number of cases suggest the virus might spread between people, but this is still being studied.
Researchers also found that CMNV is present in seafood around the world. In some regions, a large portion of fish and shrimp tested positive for the virus. This suggests that exposure may be more common than previously thought, especially in areas where seafood is frequently handled or consumed.
For eye care providers and patients, this discovery is important. Symptoms such as red eyes, pain, blurry vision, or sensitivity to light should not be ignored. Early evaluation and care can make a significant difference. As research continues, increased awareness may help protect vision and improve outcomes.