ETIDIOH - NEW

February 2025  The development of influenza candidate vaccine viruses (CVVs),  coordinated by WHO, remains an essential component of the overall global  strategy for influenza pandemic preparedness . Selection and development of  CVVs are the first steps towards timely vaccine production and do not imply a  recommendation for initiating manufacture. National authorities may consider the  use of 1 or more of these CVVs for pilot lot vaccine production, clinical trials and  other pandemic preparedness purposes based on their assessment of public health  risk and need. Zoonotic influenza viruses continue to be identified  and evolve both antigenically and genetically, leading to the need for additional  CVVs for pandemic preparedness purposes. Changes in the antigenic and genetic  characteristics of these viruses relative to existing CVVs and their potential risks  to public health justify the need to develop new CVVs. This docume...

ABSTRACT Unexpected outbreaks caused by the H5N1 highly pathogenic avian influenza virus (HPAIV) in dairy cows in the United States (US) have raised significant veterinary and public health concerns . When and how the H5N1 HPAIV was introduced into dairy cows and the broader epidemiology of influenza A virus (IAV) infections in cattle in the US remain unclear. Herein, we performed a retrospective study to screen more than 1,700 cattle serum samples collected from different bovine breeds in the US from January 2023 to May 2024 using an enzyme-linked immunosorbent assay (ELISA) targeting the nucleoprotein (NP) to detect IAV infections, and the positive samples were further tested by hemagglutination inhibition (HI) assay . Results showed that 586 of 1,724 samples (33.99%) from 15 US states were seropositive by the NP ELISA assay , including 78 samples collected in 2024 and 508 samples collected in 2023 . Moreover, the HI assay revealed that 45 of these ELISA-positive samples were positiv...

Highlights •  Scientific question :  Cross-species transmission of influenza A viruses from swine to humans occurs occasionally because their tracheal epitheliums possess both sialic acid α-2,6-Gal and α-2,3-Gal receptors . In 2011, the first human case of swine influenza virus infection in the mainland of China was detected in Jiangsu Province . Subsequently, the Eurasian avian-like H1N1 swine influenza virus (EAH1N1 SIV) had sporadically crossed the host barrier and infected humans, raising public concern for its pandemic potential. •  Evidence before this study :  A/Jiangsu/1/2011 (H1N1v) was first discovered in 2011 and belongs to the G1 genotype. The G4 and G5 genotypes that appeared successively in 2013 are recombinant H1N1 swine influenza viruses. The EAH1N1 SIVs from 2016 to the present are dominated by the G4 genotype, with hemagglutination (HA) and neuraminidase (NA) genes derived from the EAH1N1 SIVs, non-structural protein (NS) genes derived from the trip...

Highlights •  First isolation and molecular evidence of the subtype H3N2 in swine in Colombia . •  Swine H3N2 discovered is phylogenetically divergent from other viruses. •  Colombian H3N2 was originated from an independent human-to-swine spillover. •  Sequence-based analysis reveals this is a novel antigenic variant . •  Due to antigenic variation , Colombian H3N2 possess a relevant zoonotic risk. Abstract Influenza A virus (FLUAV) affects a wide range of hosts, including humans and animals, posing a threat to public health . In swine, H3N2 subtype is associated with human-to-swine spillovers of seasonal viruses . In Latin America , the molecular and antigenic characteristics of swine FLUAV H3N2, as well as its phylogenetic origin, are poorly understood. Therefore, the objective of this study was to characterize the first swine H3N2 detected in Colombia . The origin and lineage of the virus were estimated through phylogenetic and molecular clock analyses . Anti...

Abstract In 2018, a single detection of a novel reassortant swine influenza A virus (swIAV) was made in Denmark . The hemagglutinin (HA) of the virus was from the H1N1 pandemic 2009 (H1N1pdm09) lineage and the neuraminidase (NA) from the H1N1 Eurasian avian-like swine lineage (H1N1av). By 2022, the novel reassortant virus (H1pdm09N1av) constituted 27% of swIAVs identified through the Danish passive swIAV surveillance program . Sequencing detected two H1pdm09N1av genotypes; Genotype 1 contained an entire internal gene cassette of H1N1pdm09 origin, Genotype 2 differed by carrying an NS gene segment of H1N1av origin . The internal gene cassette of Genotype 2 became increasingly dominant, not only in the H1pdm09N1av population, but also in other Danish enzootic swIAV subtypes. Phylogenetic analysis of the HA genes from H1pdm09N1av viruses revealed a monophyletic source , a higher substitution rate compared to other H1N1pdm09 viruses and genetic differences with human seasonal and other swi...

Abstract Vaccination is a common influenza A virus (IAV) control strategy for pigs. Vaccine efficacy depends on strain cross-protection and effective vaccination program implementation. We evaluated a multi-faceted IAV vaccination strategy which included (a) monthly surveillance of pigs at weaning , (b) selection of epidemiologically relevant strains from farms under surveillance, (c) updating IAV strains in custom-made vaccines, and (d) seasonal mass vaccination with custom-made vaccines given to sows in 35 farrow-to-wean farms within an integrated swine farm system. Reduction of IAV in pigs from vaccinated sows was determined by monthly monitoring of farms for 30 months by IAV rRT-PCR (PCR) testing of nasal wipes collected from litters of piglets at weaning. Hemagglutinin (HA) nucleotide and amino acid (AA) sequence homology of the circulating and vaccine strains was determined by pairwise alignment and AA comparison at antigenic sites. Of the 35 farms monitored, 28 (80%) tested posi...

{Excerpt} Novel Influenza A Virus Infections One human infection with influenza A(H1N2) variant (A(H1N2)v) virus was reported by the Iowa Department of Health and Human Services . The patient is ≥18 years of age and sought health care during the week ending January 18, 2025 (Week 3), was hospitalized , and has recovered from their illness.  An investigation by state public health officials did not identify direct or indirect swine contact by the patent.  No illness was identified among the patient's close contacts.  No human-to-human transmission has been identified associated with this case. This is the first human infection with a variant influenza virus reported during the 2024-2025 season in the United States. When an influenza virus that normally circulates in swine (but not people) is detected in a person, it is called a "variant" influenza virus.  Most human infections with variant influenza viruses occur following exposure to swine, but human-to-human transmi...

Abstract Influenza A viruses (IAV) are likely candidates for pandemics . This report summarizes the results of the Swiss national program for surveillance of influenza viruses in pigs and transmissions to humans between 2010 and 2022. Challenges and optimization options in the program are discussed. Nasal swabs or lung tissue samples from pigs with influenza-like signs (e.g. fever, cough) were screened by real-time RT-PCR for swine influenza virus (SIV) genomes, including that of the 2009 pandemic strain A(H1N1)pdm09; positive samples were subtyped for H1, N1, H3 and N2 by RT-PCR and Sanger sequencing. In parallel, humans with influenza-like symptoms and recent contact to diseased pigs were asked to self-sample themselves with a nasal swab. Human swabs were tested for IAV and positive swabs further subtyped to identify potential cross-species transmission between swine and humans. In the pigs, SIV was detected in 375 of 674 farm visits . H1N1 is the only subtype detected in Swiss pigs ...

Abstract Pigs serve as a mixing vessel for influenza viruses and can independently promote the emergence of pandemic strains in humans. During our surveillance of pig populations from 2021 to 2023 in China , 11 H1 subtype swine influenza viruses (SIVs) were isolated. All viruses were reassortants , possessing internal genes of identical origins ( PB2, PB1, PA, NP, M : pdm09/H1N1 origin, NS : North American triple reassortant origin). The H1N1 isolates were all the dominant G4 EA H1N1 viruses in China. Two H1N2 isolates carried early human pdm09/H1N1 HA genes, suggesting a possible pig-to-human transmission route. Mutations that dictate host range specificity were identified in all isolates, a phenomenon which may enhance the affinity to human receptors. These H1 subtype viruses effectively replicated both in vivo and in vitro without prior adaptation and exhibited different pathogenicity and growth characteristics. Some of the H1 viruses were even found to cause lethal infections in mi...

Abstract Influenza A virus (IAV) continuously threatens animal and public health globally , with swine serving as a crucial reservoir for viral reassortment and evolution . In Chile , H1N2 and H3N2 subtypes were introduced in the swine population before the H1N1 2009 pandemic, and the H1N1 was introduced from the H1N1pdm09 by successive reverse zoonotic events . Here, we report two novel introductions of IAV H3N2 human-origin in Chilean swine during 2023. Our study reveals a closer relationship between recent human seasonal H3N2 and novel swine strains. Interestingly, one strain maintains all the genes from the original human virus , but the other strain is already a reassortment of human H3N2 and an H1N2 previously observed on the farm. Observing global IAV sequences, a similar pattern was identified in the USA confirming the reverse zoonotic potential of current seasonal human H3N2 strains. These results highlight the importance of ongoing surveillance and reinforcing biosecurity in ...

Abstract The Eurasian avian-like (EA) H1N1 swine influenza virus (SIV) possesses the capacity to instigate the next influenza pandemic , owing to its heightened affinity for the human-type α-2,6 sialic acid (SA) receptor . Nevertheless, the molecular mechanisms underlying the switch in receptor binding preferences of EA H1N1 SIV remain elusive. In this study, we conduct a comprehensive genome-wide CRISPR/Cas9 knockout screen utilizing EA H1N1 SIV in porcine kidney cells. Knocking out the enzyme gamma glutamyl carboxylase (GGCX) reduces virus replication in vitro and in vivo by inhibiting the carboxylation modification of viral haemagglutinin (HA) and the adhesion of progeny viruses, ultimately impeding the replication of EA H1N1 SIV. Furthermore, GGCX is revealed to be the determinant of the D225E substitution of EA H1N1 SIV, and GGCX-medicated carboxylation modification of HA 225E contributes to the receptor binding adaption of EA H1N1 SIV to the α-2,6 SA receptor. Taken together, our...

ABSTRACT The tonsils have been identified as a site of replication for Epstein–Barr virus, adenovirus, human papillomavirus, and other respiratory viruses. Human tonsil epithelial cells ( HTECs ) are a heterogeneous group of actively differentiating cells . Here, we investigated the cellular features and susceptibility of differentiated HTECs to specific influenza viruses , including expression of avian-type and mammalian-type sialic acid (SA) receptors , viral replication dynamics, and the associated cytokine secretion profiles. We found that differentiated HTECs possess more abundant α2,3-linked SA (preferentially bound by avian influenza viruses ) than α2,6-linked SA (preferentially bound by mammalian strains ). This dual receptor expression suggests a role in influenza virus adaptation and tropism within the tonsils by facilitating the binding and entry of multiple influenza virus strains. Our results indicated the susceptibility of differentiated HTECs to a wide range of influenza...

Abstract Zoonotic infections (swine-human) caused by influenza A viruses (IAVs) have been reported and linked to close contact between these species . Here, we describe eight human IAV variant infections ( 6 mild and 2 severe cases , including 1 death ) detected in Paraná, Brazil , during 2020–2023. Genomes recovered were closely related to Brazilian swIAVs of three major lineages (1 A.3.3.2/ pdm09, 1B/human-like, and H3.1990.5), including three H1N1v, two H1N2v, two H3N2v and one H1v. Five H1v were closely related to pdm09 lineage , one H1v ( H1N2v ) grouped within 1B.2.3 clade, and the two H3v grouped within a clade composed exclusively of Brazilian H3 swIAV (clade H3.1990.5.1). Internal gene segments were closely related to H1N1pdm09 isolated from pigs . IAV variant rarely result in sustained transmission between people, however the potential to develop such ability is of concern and must not be underestimated. This study brings into focus the need for continuous influenza surveilla...

 {Summary} Swine influenza virus (SIV) is a highly contagious pathogen that poses significant economic challenges to the swine industry and carries zoonotic potential , underscoring the need for vigilant surveillance. In this study, we performed a comprehensive genetic and molecular analysis of H3N2 SIV isolates obtained from 372 swine samples collected in Shandong Province, China . Phylogenetic analysis revealed two distinct genotypes . The surface genes of both genotypes clustered with the human-like H3N2 lineage , while the internal genes of one genotype clustered with the 2009 pandemic H1N1 (pdm/09) lineage . In the second genotype, the NS gene clustered with the classical swine (CS) H1N1 lineage , while the remaining internal genes clustered with pdm/09, suggesting stable integration of pdm/09 gene segments into H3N2 SIV. Homology analysis showed over 96% genetic similarity between the isolates and reference strains from China and Brazil , suggesting potential transmission thr...

Abstract The influenza A H1N1pdm09 virus continues to be a significant pathogen , posing potential risks to both animal and human health due to its zoonotic potential . Italy , which has one of the largest swine populations in Europe , plays a crucial role in monitoring the evolution of influenza viruses in livestock. This study aims to address the existing knowledge gaps regarding the genetic diversity and transmission dynamics of H1N1pdm09 circulating in Italian swine populations. Utilizing whole genome sequencing and dynamic modeling , we conducted a comprehensive analysis of virus samples collected from swine farms across Italy. Our results reveal that multiple independent viral introductions have occurred into the country, with most cases resulting in self-limited infections and limited onward transmission . However, six distinct transmission clusters were identified, suggesting instances of sustained viral spread. These clusters were found across multiple regions of Italy, highli...

Abstract This study evaluated influenza A virus (IAV) detection and genetic diversity over time , specifically at the human–swine interface in breeding and nursery farms . Active surveillance was performed monthly in five swine farms in the Midwest United States targeting the employees , the prewean piglets at sow farms, and the same cohort of piglets in downstream nurseries. In addition, information was collected at enrollment for each employee and farm to assess production management practices, IAV vaccination status, diagnostic procedures, and biosecurity . Farm employee and swine samples were screened by IAV reverse transcription real-time polymerase chain reaction (RT-rtPCR), followed by IAV subtyping RT-rtPCR and whole genome sequencing on PCR-positive samples. This study showed higher positivity of IAV RNA detection in nursery pigs compared to prewean pigs, and more whole genome sequences were also obtained in the nursery phase. Surveillance of farm employees revealed two detect...

 Source: BioRxIV, https://www.biorxiv.org/content/10.1101/2024.12.11.627926v1?rss=1  Abstract In 2018, a single detection of a novel reassortant swine influenza A virus (swIAV) was made in Denmark . The hemagglutinin (HA) of the virus was from the H1N1 pandemic 2009 (H1N1pdm09) lineage and the neuraminidase (NA) from the H1N1 Eurasian avian-like swine lineage (H1N1av). By 2022, the novel reassortant virus (H1pdm09N1av) constituted 27 % of swIAVs identified through the Danish passive swIAV surveillance program. Sequencing detected two H1pdm09N1av genotypes ; Genotype 1 contained an internal gene cassette of H1N1pdm09 origin , Genotype 2 differed by carrying an NS gene segment of H1N1av origin . The internal gene cassette of Genotype 2 became increasingly dominant, not only in the H1pdm09N1av population, but also in other Danish enzootic swIAV subtypes . Phylogenetic analysis of the HA genes from H1pdm09N1av viruses revealed a monophyletic source , a higher substitution rat...