Posted on 20TH MAR 2017
tagged Lassa Fever, West Africa; Nigeria

A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases

Date: Fri 3 Mar 2017
Source: Nigeria Centre for Disease Control Weekly Epidemiological Report 7 (8) [edited]

In this reporting week [EW 8], a new confirmed case of Lassa fever was reported in Borno State. Following this, there are currently 13 states affected by the outbreak, with 7 new suspected cases reported from 3 states. Following laboratory testing for Lassa fever and other VHFs, 4 of these suspected cases were confirmed positive, and 2 deaths were recorded.

Since onset of the outbreak, 247 suspected cases have been reported with 73 confirmed cases and 6 probable deaths. A total of 43 deaths have been recorded so far (37 in confirmed cases and 6 in probable cases). The case fatality rate for all cases is 21.5 percent and for all confirmed/probable cases is 54.4 percent.

The Nigeria Centre for Disease Control (NCDC) has continued to provide support (on-site and off-site) to the affected states. A team has been dispatched by the NCDC to provide support to Borno state. This was very important given the peculiar situation [violent insurgent groups] in the state, which has further created challenges with disease notification, reporting, and surveillance.

The 1st confirmed case of Lassa fever in Borno state was reported to the NCDC on 1 Mar 2017. The index case is a 32-year-old woman who presented at the hospital with a 9-day history of high-grade fever and 2-day history of bleeding from the nose and mouth.

She had a history suggestive of being exposed to rats [reservoir host of Lassa fever virus. - Mod.TY] and also poor storage of foodstuffs (uncovered foodstuff). Onset of illness was on 17 Feb 2017, and the patient 1st visited a chemist and then a traditional healer. She later presented at a health facility on 20 Feb 2017, where Lassa fever was suspected. She was put in an isolation unit and had laboratory investigations carried out; results showed she was positive for Lassa fever. The affected LGA [local government area] was notified on 21 Feb [2017], and notification was sent to the state the next day [22 Feb 2017]. Contact tracing has also been instituted.

We applaud the Borno state team for the prompt notification of this case. It is also important to highlight that the high index of suspicion among the health workers, which led to the patient's immediate isolation, played a key role in preventing further spread of the disease. We continue to encourage the general public to report immediately to a health facility if they have symptoms suggestive of Lassa fever or any VHF. We must remember that if a fever persists, it may be Lassa fever.

1. Lassa fever
Please note that the data reflects the routine reports, i.e. all suspected cases including the laboratory positive and negative cases.

1.1. 6 suspected cases of Lassa fever were reported from 5 LGAs (5 states) in week 8, 2017 compared with 10 suspected cases with 3 laboratory confirmed and one death (CFR, 10.0 percent) from 8 LGAs (5 states) at the same period in 2016 (Figure 2).
1.2. Laboratory results of the 6 suspected cases were 3 negative for Lassa fever and other VHFs, while 3 results are pending (Bauchi - 1, Plateau -1 & Taraba - 1).
1.3. Between weeks 1 and 8 (2017), 152 suspected Lassa fever cases with 38 lab-confirmed and 23 deaths (CFR, 15.13 percent) from 31 LGAs (10 states) were reported compared with 411 suspected cases with 43 lab-confirmed and 66 deaths (CFR, 16.06 percent) from 107 LGAs (26 states) at the same period in 2016 (Figure 2).
1.4. Between weeks 1 & 52 2016, 921 suspected Lassa fever cases with 109 lab-confirmed and 119 deaths (CFR, 12.92 percent) from 144 LGAs (28 states & FCT) were reported compared with 430 suspected cases with 25 lab-confirmed and 40 deaths (CFR, 9.30 percent) from 37 LGAs (14 states & FCT) at the same period in 2015 (Figure 3).
1.5. Investigation and active case searching are ongoing in affected states with coordination of all response activities by NCDC with support from partners.
1.5.1. National Lassa Fever Working Group meeting & National Surveillance and Outbreak Response meeting on-going at NCDC to assess the current Lassa fever situation in the country
1.5.2. Response materials for VHFs prepositioned across the country by NCDC at the beginning of the dry season
1.5.3. New VHF guidelines being developed by the NCDC
1.5.4. Ongoing reclassification of reported Lassa fever cases
1.5.5. Ongoing review of the variable for case-based surveillance for VHF
1.5.6. VHF case-based forms completed by affected states are being entered into the new VHF management system. This system allows for creation of a VHF database for the country.
1.5.7. Confirmed cases are being treated at identified treatment/isolation centers across the states with Ribavirin and necessary supportive management also instituted
1.5.8. Onsite support was earlier provided to Ogun, Nasarawa, Taraba and Ondo.
1.5.9. NCDC distributed Ribavirn tablets to Cross-River State.
1.5.10. States are enjoined to intensify surveillance.

Communicated by:
Olutayo Olajide Babalobi
Lecturer and Consultant Epizootiologist,
(One Health, Participatory Epizootiology and Veterinary ICT Research Group),
Department of Veterinary Public Health and Preventive Medicine,
Faculty of Veterinary Medicine,
University of Ibadan, Ibadan,

[Dr. Olutayo Olajide Babalobi is thanked for sending in this report.

Nigeria is beginning to expand its surveillance with laboratory support to speed up diagnosis and response to Lassa fever and other diseases.

As noted in earlier comments, Lassa fever remains a problem in Nigeria because the virus is endemic there. Virus transmission to humans occurs when people are in contact with the reservoir rodent host, the multimammate mouse (in the genus _Mastomys_) or their excreta. Transmission also occurs in health facilities when personal protection equipment is not employed and barrier nursing practices are not adequate to protect staff from blood and secretions of infected patients.

As noted in earlier, prevention and control of Lassa fever in nature depends on control of the rodent reservoir, which occurs across Nigeria and beyond. Reduction of populations of this rodent will require active participation at the village level. That will necessitate mounting a public education program with support of rodent control technicians. Preventing entry of rodents into the home and keeping food materials tightly covered are helpful measures to prevent infection. Elimination of these rodents completely is probably not possible.

The above report contains several interesting maps of Lassa fever distribution. Interested readers can see them at the above URL.

Images of _Mastomys_ mice can be seen at

Maps of Nigeria can be accessed at and - Mod.TY]

See Also
Lassa fever - West Africa (10): Benin, Togo, Burkina Faso 20170312.4896305
Lassa fever - West Africa (09): Nigeria (BO) 20170302.4875164
Lassa fever - West Africa (07): Nigeria (BA) 20170225.4864837
Lassa fever - West Africa (06): Nigeria 20170225.4862689
Lassa fever - West Africa (05): Nigeria (NA) 20170215.4842179
Lassa fever - West Africa (04): Liberia 20170209.4827934
Lassa fever - West Africa (03): Nigeria (RI) 20170122.4782917
Lassa fever - West Africa (02): Nigeria (NA) 20170118.4773375
Lassa fever - West Africa (01): Nigeria (OG) 20170101.4735363