Yellow fever risk assessment in the Central African Republic

Abstract

Background Starting in 2008, the Central African Republic (CAR) experienced an unprecedented number of reported yellow fever (YF) cases. A risk assessment of YF virus (YFV) activity was conducted to estimate potential disease risk and vaccine needs. Methods A multistage cluster sampling design was used to sample humans, non-human primates, and mosquitoes in distinct ecologic zones. Humans and non-human primates were tested for YFV-specific antibodies; mosquitoes were tested for YFV RNA. Results Overall, 13.3% (125/938) of humans were found to have naturally-acquired YFV antibodies. Antibody levels were higher in zones in the southern and south central regions of CAR. All sampled non-human primates (n=56) were known YFV reservoirs; one tested positive for YFV antibodies. Several known YF vectors were identified including Aedes africanus, Ae. aegypti, Ae. luteocephalus, and Ae. simpsoni. Several more urban locations were found to have elevated Breateau and Container indices for Ae. aegypti. Conclusions A country-wide assessment of YF risk found YFV to be endemic in CAR. The potential for future YF cases and outbreaks, however, varied by ecologic zone. Improved vaccination coverage through mass campaign and childhood immunization was recommended to mitigate the YF risk.

Sero-prevalence of yellow fever and related Flavi viruses in Ethiopia: a public health perspective

“…In a recent YF risk assessment done in two provinces in Zambia found YFV seroprevalence of 0.3%, which is also considered a low prevalence and was 96 to 98% lower seroprevalence compared to previous studies done in a similar provinces [ 14 ], consistent with our finding. But a similar risk assessment undertaken in Central African Republic (CAR) found a 13.3% seroprevalence of antibodies against YFV (employing a confirmatory PRNT test) in unvaccinated study participants [ 15 ] and therefore compared to the finding in CAR, Ethiopia has lower prevalence of YFV circulation based on our current survey. In another arbovirus seroprevalence study in Kenya by Luke et al [ 16 ] in 2011 found 9.2% were YFV IgG positive, which is higher than the prevalence rate reported in our study, but one of the limitations of the Kenyan study was not having employed the PRNT confirmatory test to report the findings.…”

“…In addition, by equaling distributing the number of participants to be sampled in a Zone between the two points without further adjusting for population size, we again might have limited our power to accurately assess YFV seropositivity. Our estimated participation rate (85%), which was based on other risk assessments [ 15 ], used to estimate our sample size was too high for certain locations. This lead us to sample additional households in some of the randomly selected sites effecting the representativeness of our results for some Zones.…”

Prevalence of Yellow fever virus infection and associated factors among acute febrile patients in Arbaminch districts, Southern Ethiopia

“…The overall prevalence of Yellow fever virus infection in this study was 14.9% for IgG and 7.2% for IgM. This finding is comparable to the rate reported in the Central African Republic (13.3%) [12].…”

The effect of climate change on yellow fever disease burden in Africa

“…We use these to assess transmission intensity in specific regions of the African endemic zone. The current study includes surveys from published sources ( Diallo et al, 2014 ; Kuniholm et al, 2006 ; Merlin et al, 1986 ; Omilabu et al, 1990 ; Tsai et al, 1987 ; Werner and Huber, 1984 ) and unpublished surveys from East African countries conducted between 2012 and 2015 as part of the YF risk assessment process ( Mengesha Tsegaye et al, 2018 ). The surveys were included only if they represent the population at steady state, as such outbreak investigations were omitted ( Garske et al, 2014 ).…”