Lassa Fever Outbreak in Nigeria

The World Health Organisation is increasing its response to an outbreak of Lassa fever in Nigeria. There were 450 suspected cases, of which 132 were laboratory confirmed, between 1 January and 4 February this year.  Among these, there were 43 deaths, 37 of which were confirmed by laboratory testing to be due to Lassa[i].  Lassa fever is endemic in Nigeria, but officials are concerned about the unusually high number of cases for this time of year.  By 28 February, there were 317 laboratory confirmed cases, which is more than the total number of cases confirmed in 2017.   There have been 72 deaths, and 2,845 people who have been in contact with patients are being monitored[ii].

The WHO has donated personal protective equipment to the Nigeria Centre for Disease Control and to the affected states, and procured the laboratory supplies required for rapid diagnosis of Lassa fever. Now, the WHO is deploying international experts to co-ordinate the response, strengthen surveillance, provide treatment guidelines, and engage with communities.  The WHO will also work with neighbouring countries to strengthen cross-border co-operation, as cases have also been reported in Benin, Liberia and Sierra Leone.

Lassa fever is transmitted to humans mainly through handling rats, food or objects that are contaminated by rats’ urine and faeces. It can also spread from person to person through direct contact with bodily fluids.  Lassa can be difficult to diagnose, because the early symptoms are similar to those caused by diseases such as malaria and dengue.  Most people only develop mild symptoms such as fever, headache and weakness, but Lassa is a viral haemorrhagic fever, and in severe cases can cause bleeding through the nose, mouth and other body parts.  The fatality rate is usually about 1 %, but is thought to be more than 20 % in the current outbreak[iii].  The disease is particularly dangerous in women in the later stages of pregnancy, where the death of the mother or baby occurs in 80 % of cases.  Lassa fever is similar to Ebola, which caused more than 11,000 deaths in West Africa in 2014-2015, from 28,600 suspected, probable or confirmed cases[iv].

The risk to the UK is low at this stage[v].  Similarly, the risk of an Ebola outbreak occurring in the UK remains negligible[vi], though it was reported by the BBC in 2016 that gaps in the UK’s ability to produce vaccines put the UK at risk during future epidemics[vii].


[i] WHO moves to contain Nigeria’s Lassa fever outbreak. World Health Organisation. 13 February 2018 (Accessed 6 March 2018)

[ii] Nigeria battles its largest Lassa fever outbreak on record. World Health Organisation. 28 February 2018. (Accessed 6 March 2018)

[iii] Lassa fever: The killer disease with no vaccine. BBC News. 5 March 2018. (Accessed 6 March 2018)

[iv] 2014-2016 Ebola outbreak in West Africa. Centres for Disease Control and Prevention. (Accessed 6 March 2018)

[v] Lassa fever outbreak in Nigeria prompts UK response. Boots Web MD. 5 March 2018. (Accessed 6 March 2018)

[vi] Ebola virus disease. National Health Service. (Accessed 6 March 2018)

[vii] UK is ‘vulnerable’ to next Ebola outbreak. BBC News.25 January 2016 (Accessed 6 March 2018)