Date Published: May 21, 2015
Publisher: Public Library of Science
Author(s): Sergejs Nikisins, Toni Rieger, Pranav Patel, Rolf Müller, Stephan Günther, Matthias Niedrig, Remi Charrel. http://doi.org/10.1371/journal.pntd.0003793
Abstract: Lassa virus (LASV) is a causative agent of hemorrhagic fever in West Africa. In recent years, it has been imported several times to Europe and North America. The method of choice for early detection of LASV in blood is RT-PCR. Therefore, the European Network for Diagnostics of ‘Imported’ Viral Diseases (ENIVD) performed an external quality assessment (EQA) study for molecular detection of LASV. A proficiency panel of 13 samples containing various concentrations of inactivated LASV strains Josiah, Lib-1580/121, CSF, or AV was prepared. Samples containing the LASV-related lymphocytic choriomeningitis virus (LCMV) and negative sera were included as specificity controls. Twenty-four laboratories from 17 countries (13 European, one African, one Asian, two American countries) participated in the study. Thirteen laboratories (54%) reported correct results, 4 (17%) laboratories reported 1 to 2 false-negative results, and 7 (29%) laboratories reported 3 to 5 false-negative results. This EQA study indicates that most participating laboratories have a good or acceptable performance in molecular detection of LASV. However, several laboratories need to review and improve their diagnostic procedures.
Partial Text: Lassa fever was first described in 1969 as the cause of a nosocomial outbreak of hemorrhagic fever in Nigeria . Lassa fever is an acute viral infection associated with a wide spectrum of disease manifestations, which range from mild courses to multiorgan failure [1–3]. The etiologic agent of Lassa fever is Lassa virus (LASV, family Arenaviridae, genus Arenavirus) . The natural host of LASV is the small rodent Mastomys natalensis, which lives close to human settlements . The rodents can become chronically infected at birth and excrete infectious virus in urine and other body fluids, with subsequent transmission to humans . There is evidence of human-to-human transmission in both hospital and community settings . The fact that LASV may be transmitted from human to human gives rise to nosocomial or community-based outbreaks. LASV is endemic in the countries of Nigeria, Liberia, Sierra Leone, and Guinea [8, 9] and was detected in Mali [10, 11]. Seroepidemiological studies and imported cases of Lassa fever indicate that arenaviruses circulate somewhere in the region comprising Côte d’Ivoire and Burkina Faso . The annual incidence is estimated at 300,000 cases, with 5,000 fatalities per year [13, 14]. Additionally, LASV has been introduced several times into Europe, Japan, and North America. Among the hemorrhagic fever viruses of risk group 4 (such as Crimean-Congo hemorrhagic fever, Ebola, and Marburg virus), LASV has been most frequently imported . The virus usually is imported by returning travelers [16, 17]. Within Europe, LASV infections have been imported to Germany [18, 19], The Netherlands  and the United Kingdom .
Twenty-four (86%) of the 28 laboratories, which received the EQA material, reported results. The 24 participating laboratories, located in 17 countries—13 European, one African, one Asian, and two American countries (Table 1). The LASV detection rate varied among laboratories and scores ranged from 9 to the maximum of 14 (Table 2). Average score for all participating laboratories was 13 points. Good results were achieved by 13 (54%) laboratories, 4 (17%) laboratories achieved acceptable results, and 7 (29%) laboratories had need for improvement. Table 3 shows that 13 (54%) laboratories correctly detected LASV in all 12 LASV samples (100% detection rate). Three (12%) participants had one false negative result (92% detection rate). Eight participants had a detection rate between 58% and 83%. None of the laboratories reported false-positive results for the negative control samples.