Cluster of human Puumala orthohantavirus infections due to indoor exposure?-An interdisciplinary outbreak investigation

Abstract

Puumala orthohantavirus (PUUV) is the most important hantavirus species in Europe, causing the majority of human hantavirus disease cases. In central and western Europe, the occurrence of human infections is mainly driven by bank vole population dynamics influenced by beech mast. In Germany, hantavirus epidemic years are observed in 2- to 5-year intervals. Many of the human infections are recorded in summer and early autumn, coinciding with peaks in bank vole populations. Here, we describe a molecular epidemiological investigation in a small company with eight employees of whom five contracted hantavirus infections in late 2017. Standardized interviews with employees were conducted to assess the circumstances under which the disease cluster occurred, how the employees were exposed and which counteractive measures were taken. Initially, two employees were admitted to hospital and serologically diagnosed with hantavirus infection. Subsequently, further investigations were conducted. By means of a self-administered questionnaire, three additional symptomatic cases could be identified. The hospital patients' sera were investigated and revealed in one patient a partial PUUV L segment sequence, which was identical to PUUV sequences from several bank voles collected in close proximity to company buildings. This investigation highlights the importance of a One Health approach that combines efforts from human and veterinary medicine, ecology and public health to reveal the origin of hantavirus disease clusters.

Keywords: Clethrionomys glareolus; Puumala orthohantavirus; One Health initiative; hantavirus outbreak; occupational exposure.

FIGURE 1

1 Consensus phylogenetic tree of outbreak related Puumala orthohantavirus (PUUV) L segment sequences with a length of 325 nt (with geographic reference “Bentheim”) and other human‐derived PUUV sequences from neighboring geographic areas (see Weiss et al., 2019) and bank‐vole derived PUUV sequences. The consensus phylogenetic tree is based on Bayesian analyses with 8,000,000 generations and a burn‐in fraction of 25% and on Maximum‐Likelihood analyses with 1,000 bootstrap replicates. The Hasegawa, Kishino and Yano substitution model with invariant sites and a gamma distributed shape parameter (HKY+I+G) was used for Bayesian and the Jukes‐Cantor including the categories model (JC+CAT) for Maximum‐Likelihood tree reconstructions. Posterior probabilities are given in front and bootstrap values behind the slash if branches are supported with values above 50 and if branches of both trees were consistent. CE Central European lineage; cg Clethrionomys glareolus; FIN Finnish lineage; hu human; HOKV Hokkaido virus; LAT Latvian lineage; MUJV Muju virus; N‐SCA North‐Scandinavian lineage; RUS Russian lineage; TULV Tula orthohantavirus

FIGURE 2

Map showing the locations where the samples from the phylogenetic tree in Figure 1 were collected (see Weiss et al., 2019). The outbreak site is represented by the top‐left dot