Dataset Information

Potential for Seasonal Lassa Fever Case Exportation from Nigeria.

ABSTRACT: The largest epidemic of Lassa fever in recent history occurred in Nigeria in 2018. We assessed the potential for cases of Lassa fever originating in Nigeria to arrive at international destinations via air travel using a probabilistic model. We estimated no exported cases in 62% of 1,000 model simulations. In 30% of simulations, a single exported case was projected. Greater than 40% of outbound travelers from Nigeria arrived in the United States, the United Kingdom, and Ghana, placing these countries at greatest risk for receiving an exported case. There was a wide range in the capacity of highly connected countries to respond to infectious disease threats, as measured by the Infectious Disease Vulnerability Index. Although we quantified a low probability of case exportation during this outbreak, countries with the greatest connectivity to Nigeria should be alert to the potential risks of Lassa fever importation and be prepared to manage infected individuals.

SUBMITTER: Tuite AR

PROVIDER: S-EPMC6402922 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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Potential for Seasonal Lassa Fever Case Exportation from Nigeria.

Tuite Ashleigh R AR Watts Alexander G AG Kraemer Moritz U G MUG Khan Kamran K Bogoch Isaac I II

The American journal of tropical medicine and hygiene 20190301 3

The largest epidemic of Lassa fever in recent history occurred in Nigeria in 2018. We assessed the potential for cases of Lassa fever originating in Nigeria to arrive at international destinations via air travel using a probabilistic model. We estimated no exported cases in 62% of 1,000 model simulations. In 30% of simulations, a single exported case was projected. Greater than 40% of outbound travelers from Nigeria arrived in the United States, the United Kingdom, and Ghana, placing these count ...[more]

PMID: 30693858

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Project description:Annual outbreaks of Lassa fever have resulted in a public health threat in Nigeria and other endemic countries in Sub-Saharan Africa. While the Lassa Virus (LASV) is endemic in rodent populations, zoonotic spillover to humans causes annual outbreaks. This study reviewed the burden of Lassa fever (LF) in Nigeria between 2020 and 2023 and conducted a cross-sectional survey of Nigerians to evaluate their risk perceptions of LF. During the period under review, 28,780 suspected and 4,036 confirmed cases of LF were reported from 34 of the 37 states of Nigeria. These cases resulted in 762 deaths (a CFR of 18.9%). The overall case positivity rate was 14% (4,036/28,780), with more positive cases in 2020 (17.5%, n = 1,189/6,791). A total of 2,150 study participants were enrolled in the prospective cross-sectional study, with most of them (87.5%, n = 1,881/2,150) having previously heard of Lassa fever (LF). The numerical scoring system revealed that 35.43% (n = 762/1,881) of those aware of LF have poor knowledge of its preventive measures, route of transmission, and control measures. Approximately 6.84% (n = 147/2,150) of them were at a high risk of contracting LF, with 27.6% (n = 584/2,150) of study participants feeling concerned about contracting LF because of the presence of rodents in their immediate vicinity, occupational exposure to healthcare workers, and the probability of contamination of food by infected rodents without necessary food safety measures. Multivariable logistic regression analysis revealed that tertiary education was associated with an increased likelihood of better LF knowledge (OR: 17.32; 95% CI: 10.62, 28.26; p < 0.01) and a lower risk of contracting LF when compared to respondents with no formal education. In addition, study participants who reside in low-burden states have lower LF perception than those residents in high-LF-burden states (OR: 0.59; 95% CI: 0.38-0.91; p = 0.049). On the other hand, study participants with poor risk perception (knowledge) of LF had a higher likelihood (RR: 0.33; 95% CI: 0.20, 0.53; p < 0.01) of contracting LF when compared to those with good knowledge of LF. Similarly, those residents in low LF burden states were less likely (OR: 0.09; 95% CI: 0.05,0.17; p < 0.01) to contract LF when compared to those residents in high burden states. There is a need to improve LF diagnostics capacity, infection prevention and control measures, and implementation of the One Health approach to controlling LASV from animal reservoirs. In addition, public enlightenment campaigns to address fundamental knowledge gaps are crucial to mitigating the ongoing and future impact of LF in Nigeria.

Project description:The dynamics of Lassa virus (LASV) infections in rodent reservoirs and their endemic human caseloads remain poorly understood. During the endemic period, human infections are believed to be associated with the seasonal migration of Mastomys natalensis, thought to be the primary reservoir that triggers multiple spillovers of LASV to humans. It has become imperative to improve LASV diagnosis in rodents while updating their prevalence in two regions of Lassa fever endemicity in Nigeria. Rodents (total, 942) were trapped in Ondo (531) and Ebonyi (411) states between October 2018 and April 2020 for detection of LASV using various tissues. Overall, the LASV prevalence was 53.6%. The outbreak area sampled in Ondo had three and two times higher capture success and LASV prevalence, respectively, than Ebonyi State. This correlated with the higher number of annual cases of Lassa fever (LF) in Ondo State versus Ebonyi State. All rodent genera (Mastomys, Rattus, Crocidura, Mus, and Tatera) captured in both states showed slightly variable LASV positivity, with Rattus spp. being the most predominantly infected (77.3%) rodents in Ondo State versus Mastomys spp. (41.6%) in Ebonyi State. The tissues with the highest LASV positivity were the kidneys, spleen, and testes. The finding of a relatively high LASV prevalence in all of the rodent genera captured highlights the complex interspecies transmission dynamics of LASV infections in the reservoirs and their potential association with increased environmental contact, as well as the risk of zoonotic spillover in these communities, which have the highest prevalence of Lassa fever in Nigeria. IMPORTANCE Our findings show the highest LASV positivity in small rodents ever recorded and the first direct detection of LASV in Tatera spp. Our findings also indicate the abundance of LASV-infected small rodents in houses, with probable interspecies transmission through vertical and horizontal coitus routes. Consequently, we suggest that the abundance of different reservoir species for LASV may fuel the epizootic outbreaks of LF in affected human communities. The high prevalence of LASV with the diversity of affected rodents has direct implications for our understanding of the transmission risk, mitigation, and ultimately, the prevention of LF in humans. Optimal tissues for LASV detection in rodents are also presented.

Dataset Information

Potential for Seasonal Lassa Fever Case Exportation from Nigeria.

Publications

Potential for Seasonal Lassa Fever Case Exportation from Nigeria.

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