Lassa Fever is a viral haemorrhagic illness that damages organs and ruptures blood vessels. According to GAVI, every one in five people infected with the Lassa virus has severe disease affecting the liver, spleen, or kidneys.
It is often transmitted by the urine or faeces of Mastomys rats, which are native to Africa, via contaminated household objects. Once the infection jumps from animal to human, it can further be transmitted to other humans who may come in contact with the blood or organ tissue of a patient.
Even after recovery, a Lassa fever infection can result in long-term hearing loss.
While Ebola and Marburg cause sporadic and deadly outbreaks and then subside, Lassa fever occurs more regularly and sticks around for longer. In several West African countries, where outbreaks have occurred, the infection has killed between 1% to 15% of those infected.
Due to the limited amount of surveillance and little evidence about deaths in the region, there is no exact tally of how many lives the virus has claimed so far. Experts estimate there are between 100,000 and 300,000 infections of Lassa fever annually, with around 5,000 deaths overall.