Following the emergence of H7N9 influenza in March 2013, local animal and public health authorities in China have been closing live bird markets as a measure to try to control the H7N9 influenza epidemic. The role of live bird market (LBM) closure on the spread of N7N9 influenza following the closure of LBMs during March to May 2013 (the first wave) and October 2013 to March 2014 (the second wave) is described in this paper. Different provinces implemented closure actions at different times, and intensive media reports on H7N9 in different provinces started at different times. Local broiler prices dropped dramatically in places with outbreaks and more live chickens were transported to other LBMs in neighboring areas without human cases from infected areas when live bird markets were being closed. There were six clusters of human infection from March to May 2013 and October 2013 to March 2014 and there may have been intensive poultry transportation among cluster areas. These findings provide evidence that the closure of LBMs in early waves of H7N9 influenza had resulted in expansion of H7N9 infection to uninfected areas. This suggests that provincial authorities in inland provinces should be alert to the risks of sudden changes in movement patterns for live birds after LBM closure or increased publicity about LBM closure.

How influenza A viruses host-jump from animal reservoir species to humans, which can initiate global pandemics, is a central question in pathogen evolution. The zoonotic and spatial origins of the influenza virus associated with the "Spanish flu" pandemic of 1918 have been debated for decades. Outbreaks of respiratory disease in US swine occurred concurrently with disease in humans, raising the possibility that the 1918 virus originated in pigs. Swine also were proposed as "mixing vessel" intermediary hosts between birds and humans during the 1957 Asian and 1968 Hong Kong pandemics. Swine have presented an attractive explanation for how avian viruses overcome the substantial evolutionary barriers presented by different cellular environments in humans and birds. However, key assumptions underpinning the swine mixing-vessel model of pandemic emergence have been challenged in light of new evidence. Increased surveillance in swine has revealed that human-to-swine transmission actually occurs far more frequently than the reverse, and there is no empirical evidence that swine played a role in the emergence of human influenza in 1918, 1957, or 1968. Swine-to-human transmission occurs periodically and can trigger pandemics, as in 2009. But swine are not necessary to mediate the establishment of avian viruses in humans, which invites new perspectives on the evolutionary processes underlying pandemic emergence.

Influenza A viruses cause pandemics when they cross between species and an antigenically novel virus acquires the ability to infect and transmit between these new hosts. The timing of pandemics is currently unpredictable but depends on ecological and virological factors. The host range of an influenza A virus is determined by species-specific interactions between virus and host cell factors. These include the ability to bind and enter cells, to replicate the viral RNA genome within the host cell nucleus, to evade host restriction factors and innate immune responses and to transmit between individuals. In this Review, we examine the host barriers that influenza A viruses of animals, especially birds, must overcome to initiate a pandemic in humans and describe how, on crossing the species barrier, the virus mutates to establish new interactions with the human host. This knowledge is used to inform risk assessments for future pandemics and to identify virus-host interactions that could be targeted by novel intervention strategies.

Wild aquatic birds are the major reservoir of influenza A virus. Cloacal swabs and feces samples (n = 6595) were collected from 62 bird species in Argentina from 2006 to 2016 and screened for influenza A virus. Full genome sequencing of 15 influenza isolates from 6 waterfowl species revealed subtypes combinations that were previously described in South America (H1N1, H4N2, H4N6 (n = 3), H5N3, H6N2 (n = 4), and H10N7 (n = 2)), and new ones not previously identified in the region (H4N8, H7N7 and H7N9). Notably, the internal gene segments of all 15 Argentine isolates belonged to the South American lineage, showing a divergent evolution of these viruses in the Southern Hemisphere. Time-scaled phylogenies indicated that South American gene segments diverged between ~ 30 and ~ 140 years ago from the most closely related influenza lineages, which include the avian North American (PB1, HA, NA, MP, and NS-B) and Eurasian lineage (PB2), and the equine H3N8 lineage (PA, NP, and NS-A). Phylogenetic analyses of the hemagglutinin and neuraminidase gene segments of the H4, H6, and N8 subtypes revealed recent introductions and reassortment between viruses from the Northern and Southern Hemispheres in the Americas. Remarkably and despite evidence of recent hemagglutinin and neuraminidase subtype introductions, the phylogenetic composition of internal gene constellation of these influenza A viruses has remained unchanged. Considering the extended time and the number of sampled species of the current study, and the paucity of previously available data, our results contribute to a better understanding of the ecology and evolution of influenza virus in South America.

Psittacosis, parrot fever, is an infectious disease caused by Chlamydophila psittaci, a common pathogen among birds. The clinical course ranges from a mild flu-like illness to severe disease that requires intensive care in humans. We report three cases of severe pneumonia where C. psittaci was unexpectedly detected during routine validation of a new C. psittaci PCR assay. Psittacosis is a notifiable disease in Sweden and national statistics show that 96% of Swedish psittacosis cases were identified in five of the 24 microbiological laboratories available in the country. These five laboratories perform PCR for C. psittaci routinely in panels with other atypical pneumonia agents and/or Legionella, suggesting that psittacosis is an underdiagnosed infection in Sweden.

Four new H9N2 avian influenza viruses (AIVs) were isolated from domestic birds in Guangdong between December 2015 and April 2016. Nucleotide sequence comparisons indicated that most of the internal genes of these four strains were highly similar to those of human H7N9 viruses. Amino acid substitutions and deletions found in the HA and NA proteins indicated that all four of these new isolates may have an enhanced ability to infect humans and other mammals. A cross-hemagglutinin-inhibition assay, conducted with two vaccine strains that are broadly used in China, suggested that antisera against vaccine candidates could not provide complete inhibition of the new isolates.

The co-circulation of H5N1 and H9N2 avian influenza viruses in birds in Egypt provides reassortment opportunities between these two viruses. However, little is known about the emergence potential of reassortants derived from Egyptian H5N1 and H9N2 viruses and about the biological properties of such reassortants. To evaluate the potential public health risk of reassortants of these viruses, we used reverse genetics to generate the 63 possible reassortants derived from contemporary Egyptian H5N1 and H9N2 viruses, containing the H5N1 surface gene segments and combinations of the H5N1 and H9N2 internal gene segments, and analyzed their genetic compatibility, replication ability and virulence in mice. Genes in the reassortants showed remarkably high compatibility. Replication of most reassortants was higher than the parental H5N1 virus in human cells. Six reassortants were thought to emerge in birds under neutral or positive selective pressure, and four of them had higher pathogenicity in vivo than the parental H5N1 and H9N2 viruses. Our results indicated that H5N1-H9N2 reassortants could be transmitted efficiently to mammals with significant public health risk if they emerge in Egypt, although the viruses might not emerge frequently in birds.IMPORTANCEClose interaction between avian influenza (AI) viruses and humans in Egypt appears to have resulted in many of the worldwide cases of human infections by both H5N1 and H9N2 AI viruses. Egypt is regarded as a hot spot of AI virus evolution. Although no natural reassortant of H5N1 and H9N2 AI viruses has been reported so far, their co-circulation in Egypt may allow emergence of reassortants that may present a significant public health risk. Using reverse genetics, we report here the first comprehensive data showing that H5N1-N9N2 reassortants have fairly high genetic compatibility and possibly higher pathogenicity in mammals, including humans, than the parental viruses. Our results provide insight into the emergence potential of avian H5N1-H9N2 reassortants that may pose a high public health risk.

Future demands for food will place agricultural systems under pressure to increase production. Poultry is accepted as a good source of protein and the poultry industry will be forced to intensify production in many countries, leading to greater numbers of farms that house birds at elevated densities. Increasing farmed poultry can facilitate enhanced transmission of infectious pathogens among birds, such as avian influenza virus among others, which have the potential to induce widespread mortality in poultry and cause considerable economic losses. Additionally, the capability of some emerging poultry pathogens to cause zoonotic human infection will be increased as greater numbers of poultry operations could increase human contact with poultry pathogens. In order to combat the increased risk of spread of infectious disease in poultry due to intensified systems of production, rapid detection and diagnosis is paramount. In this review, multiple technologies that can facilitate accurate and rapid detection and diagnosis of poultry diseases are highlighted from the literature, with a focus on technologies developed specifically for avian influenza virus diagnosis. Rapid detection and diagnostic technologies allow for responses to be made sooner when disease is detected, decreasing further bird transmission and associated costs. Additionally, systems of rapid disease detection produce data that can be utilized in decision support systems that can predict when and where disease is likely to emerge in poultry. Other sources of data can be included in predictive models, and in this review two highly relevant sources, internet based-data and environmental data, are discussed. Additionally, big data and big data analytics, which will be required in order to integrate voluminous and variable data into predictive models that function in near real-time are also highlighted. Implementing new technologies in the commercial setting will be faced with many challenges, as will designing and operating predictive models for poultry disease emergence. The associated challenges are summarized in this review. Intensified systems of poultry production will require new technologies for detection and diagnosis of infectious disease. This review sets out to summarize them, while providing advantages and limitations of different types of technologies being researched.

Recently, two genetically distinct influenza viruses were detected in bats in Guatemala and Peru. We conducted influenza A surveillance among four bat species in Egypt. Out of 1202 swabs, 105 were positive by RT-PCR. A virus was successfully isolated in eggs and propagated in MDCK cells in the presence of TPCK-treated trypsin. Genomic analysis revealed that the virus was phylogenetically distinct from all other influenza A viruses. Analysis of the HA gene suggested common ancestry with other H9 viruses and the virus showed low-level of cross-reactivity with sera raised against H9N2 viruses. Bats were seropositive for the isolated viruses. The virus replicated in the lungs of experimentally infected mice. While genetically distinct, this virus shares several avian influenza virus characteristics suggesting a more recent avian host origin.IMPORTANCE Through surveillance, we isolated and characterized an influenza A virus from Egyptian fruit bats. This virus had affinity to avian-like receptors but was also able to infect mice. Our findings indicate that bats may harbor a diversity of influenza A viruses. Such viruses may have the potential to cross the species barrier to infect other species including domestic birds and mammals and possibly humans.