What's the deadly Lassa fever that's being reported after 13 years in UK?

One of the three people diagnosed with Lassa viral fever, in its latest outbreak after 13 years in the UK, has died of the disease. It is spread through contact with household items or food contaminated with urine or faeces of infected rats. Mild symptoms include slight fever, fatigue, weakness etc while severe symptoms include bleeding, difficulty breathing, vomiting etc.