Annual Incidence of Lassa Virus Infection in Southern Mali

Abstract

Abstract. Previously, we reported a high seroprevalence rate of Lassa virus antibodies in inhabitants of three villages in southern Mali where infected rodents have been demonstrated. Herein, we report a 1-year follow-up study in which we were able to collect a second blood samples from 88.7% of participants of the same cohort. We identified 23 seroconversions for IgG antibodies reactive against Lassa virus, representing an incidence of 6.3% (95% confidence interval = 3.8-8.8%). Seroconversion was frequently seen in preteenage children (12/23, 51.7%) and two household/familial clusters were identified. These results confirm active transmission of Lassa virus is occurring in southern Mali and appropriate diagnostic testing should be established for this etiological agent of severe viral hemorrhagic fever.Lassa fever is an acute infection in humans caused by Lassa virus (LASV, family Arenaviridae, genus Mammarenavirus). Like most Arenaviruses, LASV is a rodent-borne pathogen and is maintained in nature in the common multimammate rat, Mastomys natalensis. Annually, as many as 300,000 LASV infections and 5,000 deaths occur in west Africa, primarily in Sierra Leone, Liberia, Guinea, and Nigeria where the virus is considered endemic.1 The impact of LASV on the public health resources in these countries is significant with an estimated 10-30% of adult hospital admissions and 14% of all febrile disease attributed to LASV infection. 2-4Recent ecological studies conducted in response to the identification of sporadic cases of Lassa fever in other west African countries including Benin, Togo, Ghana, Cote d'Ivoire, and Mali suggest a larger region where LASV is circulating.5-11 As a result, it is likely that the overall burden of LASV infection across west Africa is underestimated.In February 2015, we conducted a serosurvey of a total of 600 inhabitants in three villages in southern Mali (Soromba, Bamba, and Banzana) where infected rodents have been documented, though few cases of Lassa fever have been recognized. 12,13 The results of the 2015 serosurvey demonstrated that village-specific prevalence rates in humans correlated with infection rates previously observed in rodent populations. In Banzana, where rodent prevalence rates were relatively low, 14.5% of study participants had detectable IgG antibodies against LASV, whereas in Soromba and Bamba, where up to 50% of sampled rodents had evidence of LASV infection, 41% and 44% of volunteers, respectively, were seropositive for LASV.12 These findings confirmed a large proportion of people in this region have been previously exposed to LASV. To ascertain the annual incidence of LASV infections in these villages, we returned in February 2016 to collect and serologically analyze blood samples from the same individuals. Ethical approval for research on human subjects was obtained from the independent institutional research boards of the Faculty of Medicine and Pharmacy of the University of Sciences Techniques and Technologies of Bamako, Mali, and the National Institutes of Heal...

A rapid research needs appraisal methodology to identify evidence gaps to inform clinical research priorities in response to outbreaks—results from the Lassa fever pilot

“…Case series and case reports were not extracted when higher level of evidence was available for all the clinical domains addressed in the article. Of the 110 articles, 52 met the data extraction criteria and 46 were extracted within the 5 days [18–27, 32–34, 36–48, 97–104, 107, 109–112, 114, 119, 121–124, 127]. Twenty-seven case series and 31 case reports were not extracted due to higher level of evidence being available for the domains addressed in the articles.…”

“…Most of the studies were set in West Africa. Fourteen studies were set in Nigeria [18, 19, 21, 22, 24, 26, 33, 34, 36, 39, 41, 42, 48, 127], seven in Sierra Leone [20, 25, 27, 40, 43, 45, 48], three in Liberia [23, 46, 48], three in Mali [32, 47, 48], and one in the USA [48]. One study was set in multiple locations [48].…”

Coronavirus and other airborne agents with pandemic potential

“…Though mostly a rodent-borne virus, LASV has also a potential for human-to-human transmission through contact with body fluids and aerosol droplets, particularly in healthcare settings in some developing countries in Africa. It is estimated that 100000-300000 people are infected with LASV every year in endemic areas 48 . Lassa fever symptomatology is highly variable, including multiorgan damage, haemorrhage, central nervous system involvement, kidney damage or gastrointestinal symptoms.…”

The S Genome Segment Is Sufficient to Maintain Pathogenicity in Intra-Clade Lassa Virus Reassortants in a Guinea Pig Model

“…The disease was soon recognized as being endemic in several West African countries, including Nigeria (Omilabu et al, 2005 ), Sierra Leone (Shaffer et al, 2014 ), Guinea (Kernéis et al, 2009 ), and Liberia (Frame et al, 1984 ; Monson et al, 1984 ). Recent data also indicate the presence of circulating strains in the surrounding countries of Mali (Safronetz et al, 2010 , 2017 ), Ghana (Dzotsi et al, 2012 ), Benin ( http://www.who.int/csr/don/13-june-2016-lassa-fever-benin/en/ ), Togo (Patassi et al, 2017 ; Whitmer et al, 2018 ), Burkina Faso (Frame, 1975 ; Swaan et al, 2002 ), and Côte d'Ivoire (Sogoba et al, 2012 ). Of the 100,000–300,000 estimated annual cases of LF, approximately 5,000 result in death (McCormick et al, 1987 ).…”