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- Large,
roughly spherical, enveloped particles (80-160nm in diameter) with helical
nucleocapsids & large, widely-spaced, spikes 20nm long. - (+) sense, single-stranded RNA (i.e. codes for amino acids). Unusual replication in that nested sets of mRNA are produced. This is thought to lead to a high frequencies of recombination and mutation which is relevant to viral pathogenesis & immunity. - Relatively fragile but can persist either in the animal or in the environment for a while. |