["Constanze": a trinational project on avian influenza in wild birds at Lake Constance]

When highly pathogenic avian influenza H5N1 (HPAI H5N1) arrived at Lake Constance in February 2006, little was known about its ecology and epidemiology in wild birds. In order to prevent virus transmission from wild birds to poultry, the adjacent countries initiated the tri-national, interdisciplinary research program <> to investigate avian influenza infections in water birds at Lake Constance. In collaboration with government agencies scientists examined the prevalence of AI virus in the region of Lake Constance for a period of 33 months, compared the effectiveness of different surveillance methods and analysed the migration behaviour of water birds. Although virus introduction from regions as far as the Ural Mountains seemed possible based on the migration behaviour of certain species, no influenza A viruses of the highly pathogenic subtype H5N1 (HPAIV) was found. However, influenza A viruses of different low pathogenic subtypes were isolated in 2.2 % of the sampled birds (swabs). Of the different surveillance methods utilised in the program the sampling of so called sentinel birds was particularly efficient.

An analysis of the spatial and temporal patterns of highly pathogenic avian influenza occurrence in Vietnam using national surveillance data

The objectives of this study were to describe the spatio-temporal pattern of an epidemic of highly pathogenic avian influenza (HPAI) in Vietnam and to identify potential risk factors for the introduction and maintenance of infection within the poultry population. The results indicate that during the time period 2004–early 2006 a sequence of three epidemic waves occurred in Vietnam as distinct spatial and temporal clusters. The risk of outbreak occurrence increased with a greater percentage of rice paddy fields, increasing domestic water bird and chicken density. It increased with reducing distance to higher population density aggregations, and in the third epidemic wave with increasing percentage of aquaculture. The findings indicate that agri-livestock farming systems involving domestic water birds and rice production in river delta areas are important for the maintenance and spread of infection. While the government’s control measures appear to have been effective in the South and Central parts of Vietnam, it is likely that in the North of Vietnam the vaccination campaign led to transmission of infection which was subsequently brought under control.

Mapping H5N1 highly pathogenic avian influenza risk in Southeast Asia

The highly pathogenic avian influenza (HPAI) H5N1 virus that emerged in southern China in the mid-1990s has in recent years evolved into the first HPAI panzootic. In many countries where the virus was detected, the virus was successfully controlled, whereas other countries face periodic reoccurrence despite significant control efforts. A central question is to understand the factors favoring the continuing reoccurrence of the virus. The abundance of domestic ducks, in particular free-grazing ducks feeding in intensive rice cropping areas, has been identified as one such risk factor based on separate studies carried out in Thailand and Vietnam. In addition, recent extensive progress was made in the spatial prediction of rice cropping intensity obtained through satellite imagery processing. This article analyses the statistical association between the recorded HPAI H5N1 virus presence and a set of five key environmental variables comprising elevation, human population, chicken numbers, duck numbers, and rice cropping intensity for three synchronous epidemic waves in Thailand and Vietnam. A consistent pattern emerges suggesting risk to be associated with duck abundance, human population, and rice cropping intensity in contrast to a relatively low association with chicken numbers. A statistical risk model based on the second epidemic wave data in Thailand is found to maintain its predictive power when extrapolated to Vietnam, which supports its application to other countries with similar agro-ecological conditions such as Laos or Cambodia. The model’s potential application to mapping HPAI H5N1 disease risk in Indonesia is discussed.

Pseudotyping of vesicular stomatitis virus with the envelope glycoproteins of highly pathogenic avian influenza viruses

Pseudotype viruses are useful for studying the envelope proteins of harmful viruses. This work describes the pseudotyping of vesicular stomatitis virus (VSV) with the envelope glycoproteins of highly pathogenic avian influenza viruses. VSV lacking the homotypic glycoprotein (G) gene (VSVΔG) was used to express haemagglutinin (HA), neuraminidase (NA) or the combination of both. Propagation-competent pseudotype viruses were only obtained when HA and NA were expressed from the same vector genome. Pseudotype viruses containing HA from different H5 clades were neutralized specifically by immune sera directed against the corresponding clade. Fast and sensitive reading of test results was achieved by vector-mediated expression of GFP. Pseudotype viruses expressing a mutant VSV matrix protein showed restricted spread in IFN-competent cells. This pseudotype system will facilitate the detection of neutralizing antibodies against virulent influenza viruses, circumventing the need for high-level biosafety containment.

Biological and protective properties of immune sera directed to the influenza virus neuraminidase

The envelope of influenza A viruses contains two large antigens, hemagglutinin (HA) and neuraminidase (NA). Conventional influenza virus vaccines induce neutralizing antibodies that are predominantly directed to the HA globular head, a domain that is subject to extensive antigenic drift. Antibodies directed to NA are induced at much lower levels, probably as a consequence of the immunodominance of the HA antigen. Although antibodies to NA may affect virus release by inhibiting the sialidase function of the glycoprotein, the antigen has been largely neglected in past vaccine design. In this study, we characterized the protective properties of monospecific immune sera that were generated by vaccination with recombinant RNA replicon particles encoding NA. These immune sera inhibited hemagglutination in an NA subtype-specific and HA subtype-independent manner and interfered with infection of MDCK cells. In addition, they inhibited the sialidase activities of various influenza viruses of the same and even different NA subtypes. With this, the anti-NA immune sera inhibited the spread of H5N1 highly pathogenic avian influenza virus and HA/NA-pseudotyped viruses in MDCK cells in a concentration-dependent manner. When chickens were immunized with NA recombinant replicon particles and subsequently infected with low-pathogenic avian influenza virus, inflammatory serum markers were significantly reduced and virus shedding was limited or eliminated. These findings suggest that NA antibodies can inhibit virus dissemination by interfering with both virus attachment and egress. Our results underline the potential of high-quality NA antibodies for controlling influenza virus replication and place emphasis on NA as a vaccine antigen. IMPORTANCE The neuraminidase of influenza A viruses is a sialidase that acts as a receptor-destroying enzyme facilitating the release of progeny virus from infected cells. Here, we demonstrate that monospecific anti-NA immune sera inhibited not only sialidase activity, but also influenza virus hemagglutination and infection of MDCK cells, suggesting that NA antibodies can interfere with virus attachment. Inhibition of both processes, virus release and virus binding, may explain why NA antibodies efficiently blocked virus dissemination in vitro and in vivo. Anti-NA immune sera showed broader reactivity than anti-HA sera in hemagglutination inhibition tests and demonstrated cross-subtype activity in sialidase inhibition tests. These remarkable features of NA antibodies highlight the importance of the NA antigen for the development of next-generation influenza virus vaccines.

Within-winter movements: a common phenomenon in the Common Pochard Aythya ferina

Waterbirds are often observed to move between different wintering sites within the same winter—for example, in response to food availability or weather conditions. Within-winter movements may contribute to the spreading of diseases, such as avian influenza, outside the actual migration period. The Common Pochard Aythya ferina seems to be particularly sensitive to infection with the highly pathogenic avian influenza virus H5N1 and, consequently, could play an important role as vectors for the disease. We describe here the within-winter movements of Pochards in Europe in relation to topography, climate, sex and age. We analysed data provided by the Euring data bank on 201 individuals for which records from different locations from the same winter (December–February) were available. The distances and directions moved within the winter varied markedly between regions, which could be ascribed to the differing topography (coast lines, Alps). We found no significant differences in terms of distances and directions moved between the sexes and only weak indications of differences between the age classes. In Switzerland, juveniles moved in more westerly directions than adults. During relatively mild winters, winter harshness had no effect on the distances travelled, but in cold winters, a positive relationship was observed, a pattern possibly triggered by the freezing of lakes. Winter harshness did not influence the directions of the movement. About 41% (83/201) of the Pochards that were recovered at least 1 km from the ringing site had moved more than 200 km. A substantial number of birds moved between central/southern Europe and the north-western coast of mainland Europe, and between the north-western coast of mainland Europe and Great Britain, whereas no direct exchange between Great Britain and central/southern Europe was observed. Within-winter movements of Pochards seem to be a common phenomenon in all years and possibly occur as a response to the depletion of food resources. This high tendency to move could potentially contribute to the spread of bird-transmitted diseases outside the actual migration period.

Role of Urbanization, Land-Use Diversity, and Livestock Intensification in Zoonotic Emerging Infectious Diseases

Emerging infectious diseases (EIDs) continue to significantly threaten human and animal health. While there has been some progress in identifying underlying proximal driving forces and causal mechanisms of disease emergence, the role of distal factors is most poorly understood. This article focuses on analyzing the statistical association between highly pathogenic avian influenza (HPAI) H5N1 and urbanization, land-use diversity and poultry intensification. A special form of the urban transition—peri-urbanization—was hypothesized as being associated with ‘hot-spots’ of disease emergence. Novel metrics were used to characterize these distal risk factors. Our models, which combined these newly proposed risk factors with previously known natural and human risk factors, had a far higher predictive performance compared to published models for the first two epidemiological waves in Viet Nam. We found that when relevant risk factors are taken into account, urbanization is generally not a significant independent risk factor. However, urbanization spatially combines other risk factors leading to peri-urban places being the most likely ‘hot-spots’. The work highlights that peri-urban areas have highest levels of chicken density, duck and geese flock size diversity, fraction of land under rice, fraction of land under aquaculture compared to rural and urban areas. Land-use diversity, which has previously never been studied in the context of HPAI H5N1, was found to be a significant risk factor. Places where intensive and extensive forms of poultry production are collocated were found to be at greater risk.

Use of a modified Delphi panel to identify and weight criteria for prioritization of zoonotic diseases in Switzerland

Zoonotic diseases have a significant impact on public health globally. To prevent or reduce future zoonotic outbreaks, there is a constant need to invest in research and surveillance programs while updating risk management strategies. However, given the limited resources available, disease prioritization based on the need for their control and surveillance is important. This study was performed to identify and weight disease criteria for the prioritization of zoonotic diseases in Switzerland using a semi-quantitative research method based on expert opinion. Twenty-eight criteria relevant for disease control and surveillance, classified under five domains, were selected following a thorough literature review, and these were evaluated and weighted by seven experts from the Swiss Federal Veterinary Office using a modified Delphi panel. The median scores assigned to each criterion were then used to rank 16 notifiable and/or emerging zoonoses in Switzerland. The experts weighted the majority of the criteria similarly, and the top three criteria were Severity of disease in humans, incidence and prevalence of the disease in humans and treatment in humans. Based on these weightings, the three highest ranked diseases were Avian Influenza, Bovine Spongiform Encephalitis, and Bovine Tuberculosis. Overall, this study provided a preliminary list of criteria relevant for disease prioritization in Switzerland. These were further evaluated in a companion study which involved a quantitative prioritization method and multiple stakeholders.

An infectious bat-derived chimeric influenza virus harbouring the entry machinery of an influenza A virus.

In 2012, the complete genomic sequence of a new and potentially harmful influenza A-like virus from bats (H17N10) was identified. However, infectious influenza virus was neither isolated from infected bats nor reconstituted, impeding further characterization of this virus. Here we show the generation of an infectious chimeric virus containing six out of the eight bat virus genes, with the remaining two genes encoding the haemagglutinin and neuraminidase proteins of a prototypic influenza A virus. This engineered virus replicates well in a broad range of mammalian cell cultures, human primary airway epithelial cells and mice, but poorly in avian cells and chicken embryos without further adaptation. Importantly, the bat chimeric virus is unable to reassort with other influenza A viruses. Although our data do not exclude the possibility of zoonotic transmission of bat influenza viruses into the human population, they indicate that multiple barriers exist that makes this an unlikely event.

Recent advances into understanding some aspects of the structure and function of mammalian and avian lungs

Recent findings are reported about certain aspects of the structure and function of the mammalian and avian lungs that include (a) the architecture of the air capillaries (ACs) and the blood capillaries (BCs); (b) the pulmonary blood capillary circulatory dynamics; (c) the adaptive molecular, cellular, biochemical, compositional, and developmental characteristics of the surfactant system; (d) the mechanisms of the translocation of fine and ultrafine particles across the airway epithelial barrier; and (e) the particle-cell interactions in the pulmonary airways. In the lung of the Muscovy duck Cairina moschata, at least, the ACs are rotund structures that are interconnected by narrow cylindrical sections, while the BCs comprise segments that are almost as long as they are wide. In contrast to the mammalian pulmonary BCs, which are highly compliant, those of birds practically behave like rigid tubes. Diving pressure has been a very powerful directional selection force that has influenced phenotypic changes in surfactant composition and function in lungs of marine mammals. After nanosized particulates are deposited on the respiratory tract of healthy human subjects, some reach organs such as the brain with potentially serious health implications. Finally, in the mammalian lung, dendritic cells of the pulmonary airways are powerful agents in engulfing deposited particles, and in birds, macrophages and erythrocytes are ardent phagocytizing cellular agents. The morphology of the lung that allows it to perform different functions-including gas exchange, ventilation of the lung by being compliant, defense, and secretion of important pharmacological factors-is reflected in its "compromise design."

Influenza A(H1N1) infection and severe cardiac dysfunction in adults: A case series

BACKGROUND: While viral myocarditis and heart failure are recognized and feared complications of seasonal influenza A infection, only limited information is available for 2009 influenza A(H1N1)-induced heart failure. METHODS AND MAIN FINDINGS: This case series summarizes the disease course of four patients with 2009 influenza A(H1N1) infection who were treated at our institution from November 2009 until September 2010. All patients presented with severe cardiac dysfunction (acute heart failure, cardiogenic shock or cardiac arrest due to ventricular fibrillation) as the leading symptom of influenza A(H1N1) infection. Two patients most likely had pre-existent cardiac pathologies, and three required catecholamine therapy to maintain hemodynamic function. Except for one patient who died before influenza A(H1N1) infection had been diagnosed, all patients received antiviral therapy with oseltamivir and supportive critical care. Acute respiratory distress syndrome due to influenza A(H1N1) infection developed in one patient. Heart function normalized in two of the three surviving patients but remained impaired in the other one at hospital discharge. CONCLUSIONS: Influenza A(H1N1) infection may be associated with severe cardiac dysfunction which can even be the leading clinical symptom at presentation. During an influenza pandemic, a thorough history may reveal flu-like symptoms and should indicate testing for H1N1 infection also in critically ill patients with acute heart failure.

The relationship between extravascular lung water and oxygenation in three patients with influenza A (H1N1)-induced respiratory failure

This case series reports the correlation between extravascular lung water (EVLW) and the partial arterial oxygen pressure/fractional inspiratory oxygen (PaO(2)/FiO(2)) ratio in three patients with severe influenza A (H1N1)-induced respiratory failure. All patients suffered from grave hypoxia (PaO(2), 26-42 mmHg) and were mechanically ventilated using biphasic airway pressure (PEEP, 12-15 mmHg; FiO(2), 0.8-1) in combination with prone positioning at 12 hourly intervals. All patients were monitored using the PICCO system for 8-11 days. During mechanical ventilation, a total of 62 simultaneous determinations of the PaO(2)/FiO(2) ratio and EVLW were performed. A significant correlation between EVLW and the PaO(2)/FiO(2) ratio (Spearman-rho correlation coefficient, -0.852; p < 0.001) was observed. In all patients, a decrease in EVLW was accompanied by an improvement in oxygenation. Serum lactate dehydrogenase levels were elevated in all patients and significantly correlated with EVLW during the intensive care unit stay (Spearman-rho correlation coefficient, 0.786; p < 0.001). In conclusion, EVLW seems increased in patients with severe H1N1-induced respiratory failure and appears to be closely correlated with impairments of oxygenatory function.