This study was designed to investigate the exposure of Nigerian cattle to influenza A virus (IAV) using serological and molecular techniques, considering the 2024 detection of Highly Pathogenic Avian Influenza (HPAI) H5N1 among cattle in the United States of America. We collected 693 blood and 54 milk samples from six Nigerian states spread across the southwest, north-central and north-east regions of Nigeria. Of these, 31 blood samples (4.5%) were seropositive for IAV nucleoprotein, whereas all milk samples tested negative. Moreover, the IAV matrix gene was not detected in any of the samples. Our findings showed that cattle seropositivity was not due to HPAI H5 exposure. To our knowledge, this represents the first evidence of IAV exposure among cattle in Nigeria. Further research is warranted to identify the risk factors that facilitate intra- and interspecies transmission of IAV within the Nigerian cattle population.

SUMMARY The 2013-2015 Ebola virus disease (EVD) epidemic is caused by the Makona variant of Ebola virus (EBOV). Early in the epidemic, genome sequencing provided insights into virus evolution and transmission, and offered important information for outbreak response. Here we analyze sequences from 232 patients sampled over 7 months in Sierra Leone, along with 86 previously released genomes from earlier in the epidemic. We confirm sustained human-to-human transmission within Sierra Leone and find no evidence for import or export of EBOV across national borders after its initial introduction. Using high-depth replicate sequencing, we observe both host-to-host transmission and recurrent emergence of intrahost genetic variants. We trace the increasing impact of purifying selection in suppressing the accumulation of nonsynonymous mutations over time. Finally, we note changes in the mucin-like domain of EBOV glycoprotein that merit further investigation. These findings clarify the movement of EBOV within the region and describe viral evolution during prolonged human-to-human transmission.