# Amarilloviruses of Aquatic Animals

## TL;DR

This paper reviews newly discovered Amarilloviruses in aquatic animals, highlighting their unique features and impact on fish and crustaceans.

## Contribution

The paper provides a comprehensive update on amarilloviruses in aquatic animals discovered through metagenomics.

## Key findings

- Amarilloviruses include pathogenic viruses like Cyclopterus lumpus virus in lumpfish.
- Infectious precocity virus is linked to iron prawn syndrome in farmed prawns.
- Flavi-like viruses have longer genomes and broader host ranges than classical flavivirids.

## Abstract

The family Flaviviridae has been expanded to include the highly divergent flavi-like viruses into three new families, Flaviviridae, Pestiviridae, and Hepaciviridae, in the order Amarillovirales. Classical flavivirids are small, enveloped viruses with positive-sense ssRNA genomes lacking a 3′ poly(A) tail and ~9.0–13.0 kb in length, with a single open reading frame (ORF) encoding structural proteins at the N-terminus and nonstructural proteins at the C-terminus. Members infect a wide range of mammals, birds, and insects, and many are host-specific and pathogenic. Although the RNA-directed RNA polymerase (RdRP) gene sequences of the flavi-like viruses group phylogenetically with those of classical flavivirids, flavi-like viruses often encode larger polyproteins and possess substantially longer genomes of up to ~40 kb, and some have a 3′ poly(A) tail. Their host range extends across the whole animal kingdom and angiosperm plants. This review describes the reported flavi-like viruses of aquatic animals, providing a meaningful update on all three new families in Amarillovirales that have been discovered using metagenomics in fish, crustaceans, mollusks, and echinoderms. These amarilloviruses include pathogenic viruses of aquatic animals, such as Cyclopterus lumpus virus (CLuV) detected in moribund lumpfish, and infectious precocity virus (IPV) found in iron prawn syndrome (IPS)-affected farmed giant freshwater prawns.