ABSTRACT
Background: In the last five years, more than 72% of annual Lassa fever cases in Nigeria occurred between January and May, commonly referred to as LF high transmission season. However, 281 LF cases were reported within this period in 2021, significantly lower than 1027 cases reported in 2020. It is generally proposed that the low LF cases may be due to the ongoing COVID 19 pandemic. This study aims to determine possible relationship between Lassa fever and COVID-19 surveillance in Nigeria between January and May 2021 Methods: The 2020 and 2021 data for LF and COVID-19 January to May were analyzed (2017-2021). Case counts were compared across states reporting confirmed cases for both diseases. Number of suspected cases and test positivity rate were used as a proxy for suspicion. Relationship between suspected and confirmed COVID-19 and LF cases in the 14 states that reported confirmed LF cases between January and May 2021 was determined using Spearman correlation coefficient and test of significance was conducted Results: There was a 42.8% reduction in the number of suspected LF cases in 2021 compared to 2020 in the 14 states that reported confirmed cases in 2021. However, a test positivity rate of 22.3% was recorded in 2020 compared to 15.1% recorded in 2021. There was a moderate positive correlation (r =0.473, p value = 0.103) between number of suspected LF and COVID-19 cases in the 14 states, but almost no correction (r=0.017, p value = 0.957) between number of confirmed LF and COVID-19 cases. Conclusion: Suspicion for LF seems to increase with increasing suspicion for COVID-19 although cumulate cases were lower than previous years. The low positivity rate for LF in 2021 suggests lower LF transmission in 2021 compared to 2020. The low number of suspected and confirmed cases may be reflective of reality and LF surveillance may not have been adversely affected by COVID-19 pandemic. Hence, the need to explore the factors responsible for the reduction in 2021 LF cases.