Specifically it is an old world arenavirus, which is enveloped, single-stranded, and bi-segmented RNA. This virus has both a large and a small genome section, with four lineages identified to date: Josiah (Sierra Leone), GA391 (Nigeria), LP (Nigeria) and strain AV. Spread
Lassa virus commonly spreads to humans from other animals, specifically the Natal multimammate mouse or African rat, also called the Natal multimammate rat (Mastomys natalensis). This is probably the most common mouse in equatorial Africa, common in human households and eaten as a delicacy in some areas.The multimammate mouse can quickly produce a large number of offspring, tends to colonize human settlements, increasing the risk of rodent-human contact, and is found throughout the west, central and eastern parts of the African continent.Once the mouse has become a carrier, it will excrete the virus throughout the rest of its lifetime through feces and urine creating ample opportunity for exposure. The virus is probably transmitted by contact with the feces or urine of animals accessing grain stores in residences. No study has proven presence in breast milk, but the high level of viremia suggests it may be possible.Individuals who are at a higher risk of contracting the infection are those who live in rural areas where Mastomys are discovered, and where sanitation is not prevalent. Infection typically occurs by direct or indirect exposure to animal excrement through the respiratory or gastrointestinal tracts. Inhalation of tiny particles of infectious material (aerosol) is believed to be the most significant means of exposure.
Xanthinuria, also known as xanthine oxidase deficiency, is a rare genetic disorder causing the accumulation of xanthine. It is caused by a deficiency of the enzyme xanthine oxidase. It was first formally characterized in 1954. Presentation
Sufferers have unusually high concentrations of xanthine in their blood and urine, which can lead to health problems such as renal failure and xanthine kidney stones, one of the rarest types of kidney stones. Causes
Type I xanthinuria can be caused by a deficiency of xanthine oxidase, which is an enzyme necessary for converting xanthine to uric acid. Type II xanthinuria and molybdenum cofactor deficiency lack one or two other enzyme activities in addition to xanthine oxidase. Treatment
There is no specific treatment beyond maintaining a high fluid intake and avoiding foods that are high in purine. References
External links

Xanthinuria at NIHs Office of Rare Diseases