The observed seasonal variation pattern and changing epidemiology of lassa viral hemorrhagic fever disease in Ondo State, Nigeria

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Background: The Lassa viral hemorrhagic fever disease (LVHFD) outbreak usually occurs in the Northern senatorial district of Ondo State, Nigeria. Precisely local government areas (LGAs) such as Ose and Owo LGAs; these are the adjacent LGAs to Edo State in Nigeria where LVHFD outbreak has been recorded highest in the country at recent times. Aim: This research was designed to disseminate a general public awareness message about the recent trend regarding the observed seasonal variation pattern in the epidemiological transmission, outbreak, and status of Lassa viral hemorrhagic fever disease in Ondo State, Nigeria. Materials and Methods: This was a retrospective observational longitudinal study carried out to report the recent trend regarding the observed seasonal variation pattern and changing epidemiology of Lassa viral hemorrhagic fever disease in Ondo State, Nigeria. The data in this study were sourced and collected from the state epidemiological records on Lassa fever (LF) at the Department of Public Health Services, Epidemiology Unit, State Ministry of Health, Akure, Ondo State, Nigeria. Results and Findings: The outbreak of the disease has been recurring since 2014 up till date (2018). LF outbreak in the period under consideration showed an increasing trend, except in 2015, where the rate of seropositively infected and confirmed cases reduced by 62.5% (dropped from 8 to 3 cases). The rate of confirmed seropositive cases increased by 533.3% in 2016 compared to 2015, 300% in 2017 compared to 2016, and 19.7% increase in 2018 compared to 2017 events. The mortality rate recorded which was also directly dependent on the rate of confirmed seropositively infected cases; it was 50% in 2014, 0% in 2015, 63.1% in 2016, 23.6% in 2017, and 25.3% in 2018. Furthermore, the peak seropositive outbreak cases for Lassa viral hemorrhagic fever disease in the year 2017 analyses occurred during February (12 cases) and August (12 cases), and then followed by June (11 cases) and December (9 cases). Conclusion: The observed seasonal variation pattern and changing epidemiology of Lassa viral hemorrhagic fever disease in Ondo State, Nigeria, can be attributed the challenging poor socioeconomic factors and persistent situations peculiar to the outbreak. The year 2017 analyses revealed that there was an all year round disease outbreak for LF in the state. This was contrary to the widely circulating report that LF outbreak is being influenced by dry seasons. The peak of the disease outbreak in the year 2017 occurred during February and August, as this is the peak months of dry seasons and wet seasons, respectively, in Ondo State, Nigeria.