High Lassa Fever activity in Northern part of Edo State, Nigeria: reanalysis of confirmatory test results

The purpose was to establish simple statistics of the effects of lassa fever in northern part of Edo State, Nigeria. Lassa fever activity in the northern part of Edo state, Nigeria, was confirmed in 2004 by laboratory analysis of samples sent to Bernhard–Nocht Institute (BNI) for Tropical Medicine Hamburg, Germany. The published report of that study is re-analysed to determine in statistical terms, what the values presented in percentages translate to in number of persons in the hospital and the area. In the year 2004, 12,000 persons presented with febrile illness at Irrua Specialist Teaching Hospital (ISTH), Irrua; 832 (6.5%) had lassa fever confirmed by reversetranscriptase- polymerase chain reaction (RT-PCR). 4,096 (32.26%) of those with febrile illness had acute infection as they tested positive for IgM antibody. 333 (33.33%) of about 1000 staff of the hospital had sub-clinical infection as they tested positive for IgG and negative for IgM antibody. At least 208 of the 832 patients (25%) of the hospital with confirmed lassa fever must have died in the year 2004. 967 (5.9%) of relatives or members of the public who had contact with infected persons had confirmed lassa fever. 555 (66.67%) of those with confirmed lassa fever are close relatives. The epidemics occur in clusters of households, houses, streets or villages. It is concluded that high lassa fever activity in the area has wider effects than what is observed in hospital admitted patients. Further seroepidemiological survey involving large population sample in the area should be carried out to establish more accurate seroepidemiological data on lassa fever. This study is expected to impact positively on the generation of political priority for the control of lassa fever in Nigeria