Viral Infections in Aquatic Organisms

Viral pathogens represent a pervasive challenge in both wild and farmed aquatic populations, inflicting significant ecological and economic impacts. Among these, nervous necrosis viruses and rhabdoviruses are notable for causing high mortality events in diverse fish species, from larval stages to adults. Transmission can occur horizontally via waterborne exposure or vertically through gametes, leading to persistent carrier states and latent infections. Environmental factors such as water temperature, salinity and stocking density modulate viral replication dynamics and outbreak severity. Molecular investigations have revealed that RNA viruses in aquatic hosts exhibit rapid evolution, generating quasispecies that facilitate immune evasion and host‐range expansion. Control measures range from enhanced biosecurity and surveillance to vaccination and selective breeding for resistance. Advances in reverse genetics and structural biology have deepened understanding of capsid assembly, receptor interactions and host immune modulation, opening avenues for targeted antiviral interventions. The global interconnectedness of aquaculture systems underscores the urgency of integrated management strategies that combine epidemiology, genomics and environmental monitoring to safeguard aquatic health and food security.

Research from Nature Portfolio

Recent studies have refined quantitative assays to gauge the infectivity of nervous necrosis virus in cultured fish‐cell lines. By precisely measuring cytopathic effect appearance relative to particle adsorption, researchers have demonstrated that infection efficiency peaks at moderate viral doses before declining, highlighting the importance of adsorption kinetics in vitro. This methodological advance allows for more accurate assessment of antiviral compounds and vaccine candidates. An earlier structural and epidemiological investigation has documented the emergence of reassortant betanodaviruses in gilthead sea bream, a species once considered resistant. Genetic characterisation of these RGNNV/SJNNV strains revealed a tropism shift accompanied by high larval mortality, emphasising the potential for novel viral genotypes to breach species barriers and the necessity for ongoing genomic surveillance in hatcheries.

Viral Infections in Aquatic Organisms publication trend

The graph below shows the total number of articles in viral infections in aquatic organisms across all publications each year (not limited to Nature Index journals).

Technical terms

Betanodavirus: A genus of non-enveloped, bisegmented RNA viruses that cause viral nervous necrosis in fish, leading to high mortality in larvae and juveniles.

Quasispecies: A dynamic population of related viral genomes within a host, generated by high mutation rates, which facilitates rapid adaptation and immune escape.

Reverse genetics: A molecular technique that constructs infectious viral clones with specific genome modifications, enabling functional analysis of viral genes and vaccine design.

Capsid protein: The viral structural protein that assembles into a shell around the genome, mediates host cell attachment, and is a principal target for neutralising antibodies.

References

1. Recombinant viral hemorrhagic septicemia virus with rearranged genomes as vaccine vectors to protect against lethal betanodavirus infection. Frontiers in Immunology (2023).
2. Integrated functional genomic analysis identifies regulatory variants underlying a major QTL for disease resistance in European sea bass. BMC Biology (2025).
3. Impact of Global Warming on the Severity of Viral Diseases: A Potentially Alarming Threat to Sustainable Aquaculture Worldwide. Microorganisms (2023).
4. In vitro infection efficiency of nervous necrosis virus alters depending on amount of viral particles adsorbed onto cells. Scientific Reports (2023).
5. Viral nervous necrosis in gilthead sea bream (Sparus aurata) caused by reassortant betanodavirus RGNNV/SJNNV: an emerging threat for Mediterranean aquaculture. Scientific Reports (2017).
6. The genetic variability and evolution of red-spotted grouper nervous necrosis virus quasispecies can be associated with its virulence. Frontiers in Microbiology (2023).
7. Crystal Structures of a Piscine Betanodavirus: Mechanisms of Capsid Assembly and Viral Infection. PLOS Pathogens (2015).
8. Marine medaka heat shock protein 90ab1 is a receptor for red-spotted grouper nervous necrosis virus and promotes virus internalization through clathrin-mediated endocytosis. PLOS Pathogens (2020).
9. Nervous Necrosis Virus Modulation of European Sea Bass (Dicentrarchus labrax, L.) Immune Genes and Transcriptome towards Establishment of Virus Carrier State. International Journal of Molecular Sciences (2023).
10. Nodavirus Colonizes and Replicates in the Testis of Gilthead Seabream and European Sea Bass Modulating Its Immune and Reproductive Functions. PLOS ONE (2015).