West Nile virus infections in Hungary: Epidemiological update and phylogenetic analysis of the Hungarian virus strains between 2015 and 2022.

Following the introduction of the West Nile virus (WNV) into Hungary in 2004, it has shortly become one of the most important human arbovirus infections, with a gradually increasing number of cases. The study aimed to summarize the current epidemiological situation in Hungary and sequence the WNV PCR-positive clinical specimens and virus isolates by next-generation whole genome sequencing (NGS) to obtain a detailed phylogenetic analysis of the circulating virus strains. Whole blood and urine samples from confirmed WNV-infected patients and WNV isolates were investigated by reverse transcription PCR assays. Genome sequencing was carried out by Sanger-method, followed by NGS on the Illumina MiSeq platform. Altogether 499 human infections were diagnosed between 2004 and 2022. A particularly remarkable increase in human WNV infections was observed in 2018, while the number of reported cases significantly decreased during the COVID-19 pandemic. Between 2015 and 2022, 15 WNV isolates, and 10 PCR-positive clinical specimens were investigated by NGS. Phylogenetic analysis revealed that the major European WNV lineage 2 clades, namely the Eastern European (or Russian) and the Central European (or Hungarian) clades, are presented in Hungary. Strains of the Balkan and other European clusters within the Central European clade are co-circulating in the country, following a characteristic geographical distribution. In Hungary, the presence and co-circulation of multiple lineage 2 WNV strains could be identified in the last few years. Therefore, in light of the 2018 WNV outbreak, sequence-based typing of the currently circulating strains could highly support outbreak investigations.

Bagaza virus and Plasmodium spp. coinfection in red-legged partridges (Alectoris rufa), in Southern Spain 2019.

Flaviviruses such as West Nile (WNV), Usutu (USUV) and Bagaza (BAGV) virus and avian malaria parasites are vector borne pathogens that circulate naturally between avian and mosquito hosts. WNV and USUV and potentially also BAGV constitute zoonoses. Temporal and spatial cocirculation and coinfection with Plasmodium spp., and West Nile virus has been documented in birds and mosquito vectors, and fatally USUV-infected passerines coinfected with Plasmodium spp. had more severe lesions. Also, WNV, USUV and BAGV have been found to cocirculate. Yet little is known about the interaction of BAGV and malaria parasites during consecutive or coinfections of avian hosts. Here we report mortality of free-living red-legged partridges in a hunting estate in Southern Spain that were coinfected with BAGV and Plasmodium spp. The outbreak occurred in the area where BAGV first emerged in Europe in 2010 and where cocirculation of BAGV, USUV and WNV was confirmed in 2011 and 2013. Partridges were found dead in early October 2019. Birds had mottled locally pale pectoral muscles, enlarged, congestive greenish-black tinged livers and enlarged kidneys. Microscopically congestion and predominantly mononuclear inflammatory infiltrates were evident and Plasmodium phanerozoites were present in the liver, spleen, kidneys, muscle and skin. Molecular testing and sequencing detected Plasmodium spp. and BAGV in different tissues of the partridges, and immunohistochemistry confirmed the presence and colocalization of both pathogens in the liver and spleen. Due to the importance of the red-legged partridge in the ecosystem of the Iberian Peninsula and as driver of regional economy such mortalities are of concern. Such outbreaks may reflect climate change related shifts in host, vector and pathogen ecology and interactions that could emerge similarly for other pathogens.

Modelling the temperature suitability for the risk of West Nile Virus establishment in European Culex pipiens populations.

Increases in temperature and extreme weather events due to global warming can create an environment that is beneficial to mosquito populations, changing and possibly increasing the suitable geographical range for many vector-borne diseases. West Nile Virus (WNV) is a flavivirus, maintained in a mosquito-avian host cycle that is usually asymptomatic but can cause primarily flu-like symptoms in human and equid accidental hosts. In rare circumstances, serious disease and death are possible outcomes for both humans and horses. The main European vector of WNV is the Culex pipiens mosquito. This study examines the effect of environmental temperature on WNV establishment in Europe via Culex pipiens populations through use of a basic reproduction number ( R 0 ${R_0}$ ) model. A metric of thermal suitability derived from R 0 ${R_0}$ was developed by collating thermal responses of different Culex pipiens traits and combining them through use of a next-generation matrix. WNV establishment was determined to be possible between 14°C and 34.3°C, with the optimal temperature at 23.7°C. The suitability measure was plotted against monthly average temperatures in 2020 and the number of months with high suitability mapped across Europe. The average number of suitable months for each year from 2013 to 2019 was also calculated and validated with reported equine West Nile fever cases from 2013 to 2019. The widespread thermal suitability for WNV establishment highlights the importance of European surveillance for this disease and the need for increased research into mosquito and bird distribution.

Wildlife susceptibility to infectious diseases at global scales.

Disease transmission prediction across wildlife is crucial for risk assessment of emerging infectious diseases. Susceptibility of host species to pathogens is influenced by the geographic, environmental, and phylogenetic context of the specific system under study. We used machine learning to analyze how such variables influence pathogen incidence for multihost pathogen assemblages, including one of direct transmission (coronaviruses and bats) and two vector-borne systems (West Nile Virus [WNV] and birds, and malaria and birds). Here we show that this methodology is able to provide reliable global spatial susceptibility predictions for the studied host-pathogen systems, even when using a small amount of incidence information (i.e., [Formula: see text] of information in a database). We found that avian malaria was mostly affected by environmental factors and by an interaction between phylogeny and geography, and WNV susceptibility was mostly influenced by phylogeny and by the interaction between geographic and environmental distances, whereas coronavirus susceptibility was mostly affected by geography. This approach will help to direct surveillance and field efforts providing cost-effective decisions on where to invest limited resources.

Diversity of West Nile and Usutu virus strains in mosquitoes at an international airport in Austria.

Increased globalization and international transportation have resulted in the inadvertent introduction of exotic mosquitoes and new mosquito-borne diseases. International airports are among the possible points of entry for mosquitoes and their pathogens. We established a mosquito and mosquito-borne diseases monitoring programme at the largest international airport in Austria and report the results for the first two years, 2018 and 2019. This included weekly monitoring and sampling of adult mosquitoes, and screening them for the presence of viral nucleic acids by standard molecular diagnostic techniques. Additionally, we surveyed the avian community at the airport, as birds are potentially amplifying hosts. In 2018, West Nile virus (WNV) was detected in 14 pools and Usutu virus (USUV) was detected in another 14 pools of mosquitoes (minimum infection rate [MIR] of 6.8 for each virus). Of these 28 pools, 26 consisted of female Culex pipiens/torrentium, and two contained male Culex sp. mosquitoes. Cx. pipiens/torrentium mosquitoes were the most frequently captured mosquito species at the airport. The detected WNV strains belonged to five sub-clusters within the sub-lineage 2d-1, and all detected USUV strains were grouped to at least seven sub-clusters among the cluster Europe 2; all strains were previously shown to be endemic in Austria. In 2019, all mosquito pools were negative for any viral nucleic acids tested. Our study suggests that airports may serve as foci of arbovirus activity, particularly during epidemic years, and should be considered when designing mosquito control and arbovirus monitoring programmes.

Expanding the Differential During the COVID-19 Pandemic: Fatal West Nile Virus Neuroinvasive Disease.

The ever-evolving pandemic of Coronavirus disease 2019 (COVID-19) has the potential to drown out other viruses continuing to infect communities. To highlight this, we present 2 cases of fatal West Nile virus neuroinvasive disease that occurred within 2 weeks of each other. Since the first positive case of West Nile virus in the United States, there have been 2 epidemics in the past 2 decades, most often occurring in regions of North Texas and Southern California, which have been areas of high-incidence for COVID-19. It is important for the health care provider to recognize diagnostic biases and maintain broad differentials for the patient presenting with fever and other symptoms associated with COVID-19.

Emergent Viral Infections of the CNS.

Biological evolution of the microbiome continually drives the emergence of human viral pathogens, a subset of which attack the nervous system. The sheer number of pathogens that have appeared, along with their abundance in the environment, demand our attention. For the most part, our innate and adaptive immune systems have successfully protected us from infection; however, in the past 5 decades, through pathogen mutation and ecosystem disruption, a dozen viruses emerged to cause significant neurologic disease. Most of these pathogens have come from sylvatic reservoirs having made the energetically difficult, and fortuitously rare, jump into humans. But the human microbiome is also replete with agents already adapted to the host that need only minor mutations to create neurotropic/toxic agents. While each host/virus symbiosis is unique, this review examines virologic and immunologic principles that govern the pathogenesis of different viral CNS infections that were described in the past 50 years (Influenza, West Nile Virus, Zika, Rift Valley Fever Virus, Hendra/Nipah, Enterovirus-A71/-D68, Human parechovirus, HIV, and SARS-CoV). Knowledge of these pathogens provides us the opportunity to respond and mitigate infection while at the same time prepare for inevitable arrival of unknown agents.