A spumavirus or foamyvirus is a genus of the retroviridaefamily. Spumaviruses are exogenous viruses that have specific morphology with prominent surface spikes. The virions contain significant amounts of double-stranded full-length DNA, and assembly is rather unusual in these viruses. Normally, the envelope membrane is acquired by budding through the endoplasmic reticulum. However, in, for example, the equine foamy virus (EFV), budding from the cytoplasmic membrane occurs.
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