Lagos - Thirty-one people have died from Lassa fever in Nigeria since the start of this year, the health minister said, with cases of the viral disease recorded across the country.Isaac Adewole told reporters in Abuja on Monday that the outbreak was currently "active in 15 states, (with) 105 laboratory-confirmed cases, three probable cases, with 31 deaths".Ten of the 31 dead were health workers, he added.Lassa fever belongs to the same family as Marburg and Ebola, two deadly viruses that lead to infections with fever, vomiting and in worst-case scenarios, haemorrhagic bleeding.In Ivory Coast, meanwhile, Health and Public Hygiene Minister Raymonde Goudou Coffie said on Tuesday that the country had stepped up vigilance "in light of the... situation in affected countries and the flow of (travellers) among the nations of the sub-region."KEEP UPDATED on the latest news from around the continent by subscribing to our FREE newsletter, Hello Africa.FOLLOW News24 Africa on Twitter and Facebook. Coffie said that no cases of the disease had been registered locally, but warned of a potential risk from countries where it is endemic, such as Nigeria and Benin, as well as neighbouring Guinea.Ivorians should go "immediately to the nearest health centre if the following symptoms appear: high fever followed by a general illness, weakness and muscle pains," Coffie said. The virus is spread through contact with food or items contaminated with rats' urine or faeces or after coming into direct contact with the bodily fluids of an infected person. It can be prevented by enhanced hygiene and avoidance of all contact with rats.The disease takes its name from the town of Lassa in northern Nigeria where it was first identified in 1969. More than one hundred people were killed in 2016 in one of the country's worst outbreaks of lassa fever, affecting 14 of the 36 states, including Lagos and the capital Abuja.