characterization of yellow fever suspected cases and confirmed outbreaks in a southwest state, nigeria, 2021

Background: yellow fever (yf) is an acute viral hemorrhagicfever caused by the yellow fever virus and transmitted by aedesmosquito species. despite the availability of a very effectivevaccine, yellow fever virus (yfv) remains a public health threatacross africa. enhanced disease surveillance, vector control, andhigh vaccination coverages are key to the prevention and controlof yf. this paper aimed to describe yellow fever surveillance inondo state and the outbreak investigation activities conducted inthe lgas where outbreaks occurred in the year 2021.methods: this is a retrospective cross-sectional study. weconducted an epidemiological investigation of yellow feversuspected and confirmed cases in ondo state in nigeria in2021, using the yf case-based surveillance data. we describedoutbreak investigation and response activities carried out inaffected lgas, where the outbreaks were confirmed.results: a total of 62 suspected yf cases were reported fromjanuary to december 2021, with no record of mortality. morethan half (53%) of the cases were between the age of 15 to 29years. about three-quarter of the reported cases (73%) hadreceived the yf vaccine. the overall attack rate was 1.33 casesper 100,000 population. only 3 out of the 62 reported cases wereconfirmed as yellow fever cases.conclusion: the resurgence of yellow fever in the state putsthe state at high-risk for yellow fever transmission. to reducethe immediate risks to the health of the population, specificactivities should be tailored towards increasing awareness onyellow fever transmission, prevention, and control. these includeactivities on risk communication and community engagement,active surveillance, vector control, strengthening of routineimmunization, as well as continued implementation of preventivemass vaccination campaigns.