Lassa fever
Lassa fever is an infectious disease caused by Lassa virus, a member of the arenavirus family. The disease was first recognised in the 1950s and the virus was later identified in the town of Lassa, Nigeria in 1969. Lassa fever is endemic in parts of West Africa, particularly Guinea, Liberia, Nigeria and Sierra Leone, where the animal reservoir, the Mastomys (multimammate) rat is common. Occasional cases and outbreaks also occur in other parts of the region, mainly in countries next to endemic areas.
People living in risk areas of West Africa are most at risk of Lassa fever. For tourists and most travellers, the risk is very low. Imported cases are unusual and are generally only reported in people who work in endemic areas in high-risk jobs, such as field and agricultural workers. More rarely, cases are sometimes reported in health professionals or aid workers.
Multimammate rats shed the virus in their urine and faeces. Lassa virus usually spreads from these rats to humans by direct contact with rat urine or droppings to broken skin or mucous membranes (usually the mouth or nose) or by contact with infected rodent urine or faeces on floors, home surfaces and in food or water. Transmission is possible when infected rodents are consumed as food and Lassa virus can spread from person to person by direct contact with infected bodily fluids, such as blood, faeces, saliva, urine, semen and vomit. People can also become infected through contact with contaminated objects, like needles. An individual can excrete Lassa virus in urine for between three and nine weeks after the onset of illness and via semen for up to three months, so sexual intercourse must be avoided for three months after recovery.
Initial symptoms may include:
- fever and shivering
- tiredness
- headache
- general aches
- sore throat
Vomiting, diarrhoea or a cough can also occur.
In the later stages of the illness, it can cause bleeding from the mouth, nose, vagina or gastrointestinal tract (stomach and guts).
Most people infected with Lassa virus have few if any symptoms, while approximately 20% of infections cause severe illness. Overall, approximately 1% of infections are fatal. Lassa fever is particularly severe in late pregnancy, with mother and/or foetus (unborn baby) deaths occurring in more than 80% of cases during the third trimester.
Early supportive care with fluid replacement and blood transfusion, and symptomatic treatment can improve survival rates. An antiviral drug called ribavirin may be useful if given early in the illness. However, recently evidence for this has been challenged and more work is needed to find the best treatment regimen.
There is currently no vaccine available for Lassa fever.
Check our Country Information pages for destination specific news and outbreaks.
Prevention
UK travellers planning to visit areas at risk of Lassa fever should consider their plans carefully, in consultation with a travel health specialist.
All travellers to Lassa fever endemic areas should:
- Avoid contact with anyone with symptoms.
- Avoid contact with blood and body fluids and items that might have been contaminated with blood and body fluids, like clothes, bedding or medical equipment.
- Avoid areas with a risk of contamination with rat urine or droppings.
- Avoid eating, cooking or preparing any meat from an unknown source.
- Always wash and peel fruit and vegetables carefully.
- Store food in rodent-proof containers.
- Follow good food, water and personal hygiene advice, including careful, regular hand washing with soap and water (or alcohol gel if soap and water is unavailable).
- Follow safer sex advice - always use a condom.
- At funerals, mourners should avoid all contact with the deceased, their body fluids and their personal property.
Field and agricultural workers, aid workers and health professionals planning to undertake humanitarian work in areas where outbreaks or isolated Lassa fever cases are reported should seek advice, training, and personal protective equipment from their employer/organisation prior to travel. They should also be familiar with information provided on the United Kingdom (UK) Health Security Agency about Lassa fever.
UK travellers experiencing symptoms abroad should seek local medical advice as soon as possible.
Travellers returning to the UK from risk areas with symptoms should phone their GP for advice or call NHS 111. Returning travellers must remember to tell their doctor or health professional they travelled abroad recently and mention every country visited.
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Recent Lassa fever Outbreaks
Lassa fever in Liberia
As of 30 August 2026, 33 cases (11 deaths) of Lassa fever have been reported since the start of the year. The outbreak remains active in Bong, Grand Bassa and Nimba counties. Please see our Topics in Brief article for further details on Lassa fever.
As of 14 June 2026, 23 cases (nine deaths) of Lassa fever have been reported since the start of the year. Bong, Bassa, and Nimba counties are reported to be experiencing outbreaks. 242 confirmed Lassa fever cases including 75 deaths have been reported in Liberia since January 2022. Please see our Topics in Brief article for further details on Lassa fever.
Source: StateBetween 6 January 2022 and 12 January 2025, 180 confirmed Lassa fever cases and 56 deaths have been reported in Liberia. Most cases were reported from Suakoko and Grand Bassa County. Please see our Topics in Brief article for further details on Lassa fever.
Source: StateA prolonged outbreak of Lassa fever has been reported in 14 out of 15 counties in Liberia. As of 15 November 2024, 212 cases (38 confirmed, 174 suspected) and 11 deaths have been reported during 2024. Please see our Topics in Brief article for further details on Lassa fever.
Source: Africa CDCSince the beginning of 2024, 11 cases of Lassa fever have been reported in Liberia.
Source: StateFrom 6 January 2022 to 28 May 2023, a total of 75 laboratory confirmed Lassa fever cases, including 20 deaths, have been reported.
Source: StateAs of 4 April 2022, a total of 46 suspected cases of Lassa fever (including 19 confirmed and 6 deaths) have been reported in Liberia since the beginning of the year.
Source: WHOLassa fever in Sierra Leone
The World Health Organisation reported that on 3 March 2026, a 36-year-old pregnant woman died in Bonthe District, Sierra Leone, after testing positive for Lassa fever. The last Lassa fever outbreak in Sierra Leone was reported in February 2025. Please see our Topics in Brief article for further details on Lassa fever.
Lassa fever in Nigeria
As of 23 August 2026, a total of 1,056 confirmed Lassa fever cases, with 7,580 suspected cases, six probable cases and 253 deaths, have been reported across 24 states in Nigeria for 2026. Please see our Topics in Brief article for further details on Lassa fever.
As of 12 July 2026, a total of 963 confirmed Lassa fever cases, with 6,554 suspected, six probable cases and 229 deaths, have been reported across 23 states in Nigeria for 2026. Please see our Topics in Brief article for further details on Lassa fever.
Source: StateAs of 10 May 2026, a total of 793 confirmed Lassa fever cases, with 5,034 suspected, five probable cases and 204 deaths, have been reported across 23 states in Nigeria for 2026. This includes 45 cases in health workers. Please see our Topics in Brief article for further details on Lassa fever.
Source: StateIn 2026, up to 29 March, 3,831 suspected, 663 confirmed and five probable cases, and 167 deaths have been reported across 22 states. Of all confirmed cases 85% were reported from five states (Bauchi, Ondo, Taraba, Edo and Benue). Please see our Topics in Brief article for further details on Lassa fever.
Source: StateAs of 22 February 2026, a total of 1,989 suspected Lassa fever cases (404 confirmed, 43 deaths) have been reported since the start of 2026. Confirmed cases have been reported in 18 states, with 84% of confirmed cases reported from Ondo, Bauchi, Edo and Taraba. Please see our Topics in Brief article for further details on Lassa fever.
Source: StateAs of 14 December 2025, a total of 9,164 suspected Lassa fever cases (1,097 confirmed with 201 deaths) have been reported since the start of 2025. Confirmed cases have been reported in 21 states, with 89% of confirmed cases reported from Ondo, Bauchi, Edo and Taraba. Please see our Topics in Brief article for further details on Lassa fever.
Source: StateBetween 1 January and 16 November 2025, a total of 8,679 suspected Lassa fever cases (995 confirmed and 184 deaths) have been reported. Cases have been reported from 21 states with 88% of confirmed cases from the states of Ondo, Bauchi, Edo and Taraba. Please see our Topics in Brief article for further details on Lassa fever.
Source: StateBetween 1 January and 14 September 2025, a total of 7,673 suspected Lassa fever cases (895 confirmed and 166 deaths) have been reported. Cases have been reported from 21 states, and 90 percent of confirmed cases are from the states of Ondo, Bauchi, Edo, Taraba and Ebonyi. Please see our Topics in Brief article for further details on Lassa fever.
Source: StateBetween 1 January and 13 July 2025, a total of 6,520 suspected Lassa fever cases (811 confirmed and 152 deaths) have been reported. Cases have been reported from 21 states this year, 89 percent of confirmed cases are from Ondo, Taraba, Bauchi, Edo, and Ebonyi states. Please see our Topics in Brief article for further details on Lassa fever.
Source: StateAs of 29 June 2025, a total of 6,109 suspected cases of Lassa fever, (790 confirmed) including 148 deaths have been reported in Nigeria during 2025. 20 states have reported at least one case, the majority from Bauchi, Taraba and Ondo states. Please see our Topics in Brief article for further details on Lassa fever.
Source: StateAs of 18 May 2025, a total of 5,118 suspected cases of Lassa fever, (733 confirmed) including 141 deaths have been reported in Nigeria during 2025. 18 states have reported at least one case, the majority from Bauchi, Taraba and Ondo states. Please see our Topics in Brief article for further details on Lassa fever.
Source: StateAs of 30 March 2025, a total of 3,779 suspected cases of Lassa fever, (659 confirmed) including 122 deaths have been reported in Nigeria during 2025. 18 states have reported at least one case, the majority from Bauchi, Edo and Ondo. Please see our Topics in Brief article for further details on Lassa fever.
Source: StateAs of 23 February 2025, 2,492 suspected cases of Lassa fever, (506 confirmed) and 6 deaths have been reported in Nigeria in 2025. 12 states have reported at least one case, the majority from Bauchi, Edo and Ondo. Please see our Topics in Brief article for further details on Lassa fever.
Source: StateBetween 12-19 January 2025, 359 suspected and 71 confirmed cases and 17 deaths from Lassa fever have been reported. In 2025, 10 states have reported at least one case, the majority from Bauchi, Edo and Ondo. Please see our Topics in Brief article for further details on Lassa fever.
Source: StateAs of 16 December 2024, a total of 10,450 cases, including 184 deaths, of Lassa fever have been reported in 28 of 36 states and the federal capital district during 2024. Please see our Topics in Brief article for further details on Lassa fever.
Source: Africa CDCAs of 6 September 2024, a total of 9,256 cases of Lassa fever (1,005 confirmed and 8,251 suspected) have been reported from 28 of 36 states and the federal capital territory this year.
Source: Africa CDCAs of 22 April 2024, 5,669 suspected, 832 confirmed and 17 probable cases, including 152 deaths, have been reported. In total for 2024, 27 states have recorded at least 1 confirmed case across 126 Local Government Areas.
Source: StateSince the beginning of 2024, 1,995 cases and 68 deaths have been reported in Nigeria.
Source: StateAs of 18 January 2024, in the first week of 2024, 53 confirmed cases have been reported from 9 states, including 6 deaths. This compares to 29 confirmed cases (including 8 deaths) reported from 6 states in the first week of 2023. Cumulatively, 9,155 suspected cases, 1,270 confirmed cases and 227 deaths were reported for 2023 (across 28 states and 124 LGAs).
Source: StateAs of 16 June 2023, 5,822 suspected and 957 confirmed cases of Lassa Fever, including 164 deaths among confirmed cases, have been reported. Cases have been confirmed in 28 States across 106 Local Government Areas.
Source: StateAs of 7 May 2023, in total for 2023, 28 States have recorded at least one confirmed case of Lassa fever across 106 Local Government Areas.
Source: StateAs of 16 April 2023, a total of 4,702 suspected, 5 probable and 877 confirmed cases of Lassa fever have been reported since the start of the year. Among the confirmed cases, there have been 152 deaths. Cases have been reported from 101 local government areas, in 26 out of 36 states, including the Federal Capital Territory.
Source: WHOAs of 30 January 2023, the Nigerian authorities have stated that there is an unprecedented upward trend in confirmed Lassa fever cases, compared to previous years. A total of 244 confirmed cases, with 37 deaths, have been reported in 2023, with an increased risk of healthcare worker infections and deaths.
Source: StateAs of 2 October 2022, cumulatively from week 1 to week 39 in 2022, 933 confirmed cases including 173 deaths have been reported. The majority of cases are from Ondo State, the others from Edo and Bauchi States.
Source: StateBetween 1 January and 13 March 2022, a total of 630 laboratory confirmed Lassa fever cases including 112 deaths have been reported across 23 states.
Source: StateFrom 3 to 30 January 2022, 211 laboratory confirmed Lassa fever cases including 40 deaths have been reported in 14 states.
Source: WHOBetween 1 and 16 January 2022, a total of 96 confirmed cases of Lassa fever, with 11 deaths have been reported across 11 states. Of all confirmed cases most were reported from Edo, Ondo and Bauchi states.
Source: WHODuring 2021, a total of 510 cases of Lassa fever with 102 deaths have been confirmed across 17 states. Of all confirmed cases, most were reported in Edo , Ondo and Bauchi states.
Source: WHOBetween 1 January and 12 September 2021, a total of 3,006 suspected cases of Lassa fever were reported with 369 confirmed and 76 deaths. Of all confirmed cases, 84% are from Edo (45%), Ondo (34%) and Taraba (5%) States.
Source: WHOA total of six new confirmed cases were reported from four states (Ondo, Edo, Bauchi and Ebonyi) in the week ending 27 December 2020. From 1 January to 27 December 2020, a total of 1,195 cases (1,181 confirmed and 14 probable) with 244 deaths were reported across 27 states in Nigeria.
Source: WHOAs of 11 October 2020, a total of five new confirmed cases of Lassa fever with one death were reported from three states - Ondo (three cases with one death), Edo (one case), and Ebonyi (one case) in week ending 11 October 2020. So far this year, a total of 1,117 cases (1,103 confirmed and 14 probable) with 242 deaths have been reported from 129 Local Government Areas across 27 states in Nigeria.
Source: WHOAs of 14 March 2020, a total of 3,735 suspected Lassa fever cases, 906 confirmed cases and 161 deaths have now been reported in 2020. A total of 27 States have now recorded at least one confirmed Lassa fever case in 2020.
Source: Nigerian Centre for Disease ControlThe outbreak of Lassa fever is rapidly expanding, with the number of new reported cases increasing weekly and new states being affected. Between 1 January and 2 February 2020, a total of 1,226 suspected cases were reported. Among these, a total of 365 confirmed cases were recorded from 23 states. The majority of confirmed cases are from Edo (35%), Ondo (35%) and Ebonyi (6%) states. Among the 365 confirmed cases, 47 deaths have occurred.
Source: WHOBetween 1 and 19 January 2020, a cumulative total of 398 suspected cases of lassa fever was reported nationally. Among these, a total of 163 confirmedcases was identified from 32 Local Government Areas. 793 confirmed cases were reported in 2019.
Source: WHOAs of 1 December 2019, a total of 793 confirmed (and 19 probable) Lassa fever cases have been reported from 23 states since 1 January 2019.
Source: StateAs of 12 May 2019, a total of 569 confirmed cases and 128 deaths, have been reported from 21 states.
Source: StateBetween 1 January and 3 March 2019, a total of 420 confirmed cases, including 93 deaths, have been reported from 21 states.
Source: StateFrom 1 January to 10 February 2019, 327 cases of Lassa fever (324 confirmed and 3 probable) with 72 deaths have been reported across 20 states and the Federal Capital Territory. The majority of cases were reported from Edo (108) and Ondo (103) states. Twelve cases have been reported among healthcare workers in seven states.
Source: WHOOn 22 January 2019, the Nigeria Centre for Disease Control (NCDC) declared an outbreak of Lassa fever in the country. From 1 January to 27 January 2019, a total of 213 confirmed and two probable Lassa fever cases, with 42 deaths have been reported across 40 local government areas in 16 states.
Source: WHOFrom 1 - 20 January 2019, a total of 136 confirmed cases have been reported across nine states.
Source: WHOFrom 1 January to 13 January 2019, there were 60 confirmed cases. As of the 6 January, eight states (Edo, Ondo, Bauchi, Nasarawa Ebonyi, Plateau, Taraba and FCT) have recorded at least one confirmed case.
Source: StateBetween 1 January 2018 to 2 December 2018, a total of 3229 suspected cases have been reported: 581 confirmed, 17 probable and 2631 negative. A total of 164 deaths have been reported: 147 confirmed cases, and 17 in probable cases. 9193 contacts have been identified from 23 states and are being followed up.
Source: StateAs of 20 April 2018, WHO advises that from 1 January to 15 April 2018, a total of 1,849 suspected cases have been reported: 413 confirmed, nine probable, 1,422 negative and were classified as non cases, and five with laboratory results are pending. 114 deaths have been reported. 27 health workers have been infected since 1 January 2018, with eight deaths.
Source: WHOBetween 1 January and 8 April 2018, a total of 1,781 suspected cases have been reported from 20 states: 408 confirmed, nine probable, 351 negative and 13 awaiting results. 27 health workers, with six deaths, have been affected since the start of this outbreak.
Source: StateAs of 23 March 2018, a cumulative total of 1,495 cases (376 confirmed) with 119 deaths have been reported January through 18 March 2018 across 19 states: Anambra, Bauchi, Benue, Delta, Ebonyi, Edo, Ekiti, Federal Capital Territory, Gombe, Imo, Kaduna, Kogi, Lagos, Nasarawa, Ondo, Osun, Plateau, Rivers, and Taraba. Healthcare workers have been affected during this outbreak (17 cases with four deaths).
Source: WHOAs 11 March 2018, a total of 1,386 cases (365 confirmed) with 114 deaths have been reported since December 2017 across 19 states: Edo, Ondo, Bauchi, Nasarawa, Ebonyi, Anambra, Benue, Kogi, Imo, Plateau, Lagos, Taraba, Delta, Osun, Rivers, FCT, Gombe, Ekiti, and Kaduna. Among the cases are 16 healthcare workers.
Source: StateAs of 4 March 2018, a total of 1121 suspected cases (353 confirmed, 8 probable and 37 awaiting laboratory results) with 110 deaths have now been reported.
Source: StateAs 25 February 2018, a total of 1,081 cases (317 confirmed) with 72 deaths have been reported since December 2017 across 18 states: Edo, Ondo, Bauchi, Nasarawa, Ebonyi, Anambra, Benue, Kogi, Imo, Plateau, Lagos, Taraba, Delta, Osun, Rivers, FCT, Gombe, and Ekiti. Among the cases are 14 healthcare workers.
Source: StateAs 18 February 2018, a total of 913 cases (272 confirmed) with 59 deaths have been reported since December 2017 across 17 states: Edo, Ondo, Bauchi, Nasarawa, Ebonyi, Anambra, Benue, Kogi, Imo, Plateau, Lagos, Taraba, Delta, Osun, Rivers, FCT, and Gombe. Among the cases are 14 healthcare workers.
Source: StateAs 11 February 2018, a total of 615 cases (193 confirmed) with 57 deaths have been reported since December 2017 across 17 states: Edo, Ondo, Bauchi, Nasarawa, Ebonyi, Anambra, Benue, Kogi, Imo, Plateau, Lagos, Taraba, Delta, Osun, Rivers, FCT, and Gombe. Among the cases are 14 healthcare workers.
Source: StateBetween 1 January and 4 February 2018, nearly 450 suspected cases were reported, of which 132 are laboratory confirmed Lassa fever. Of these, 43 deaths were reported, 37 of which were lab confirmed. Cases have been reported in 17 states.
Source: WHOAs of 28 January 2018, a total of 297 cases (77 confirmed) with 21 deaths have been reported in thirteen states (Edo, Ondo, Bauchi, Nasarawa, Ebonyi, Anambra, Benue, Kogi, Imo, Plateau, Lagos, Taraba and Delta) between 1 and 28 January 2018. Ten healthcare workers are among the cases (10) and deaths (4).
Source: StateAs of 24 January 2018, a total of 107 cases (61 confirmed) with 16 deaths have been reported in ten states (Edo, Ondo, Bauchi, Nasarawa, Ebonyi, Anambra, Benue, Kogi, Imo, Lagos) between 1 and 21 January 2018. Ten healthcare workers are among the cases (10) and deaths (3).
Source: StateOn 15 January 2018, four cases of Lassa fever in health workers, with three deaths, were confirmed.
Source: StateAs of 24 December 2017, a total of 1,022 suspected cases and 127 deaths have been reported since December 2016. The outbreak is active in six states: Ondo, Edo, Plateau, Bauchi, Kaduna, and Nasarawa.
Source: StateAs of 3 March 2017, the first case in Borno State since 1969 has been reported.
Source: WHO
