Editorial commentary: pandemic H5N1: receding risk or coming catastrophe?

Influenza A(H7N9) Virus Antibody Responses in Survivors 1 Year after Infection, China, 2017

Avian influenza A(H7N9) virus has caused 5 epidemic waves in China since its emergence in 2013. We investigated the dynamic changes of antibody response to this virus over 1 year postinfection in 25 patients in Suzhou City, Jiangsu Province, China, who had laboratory-confirmed infections during the fifth epidemic wave, October 1, 2016–February 14, 2017. Most survivors had relatively robust antibody responses that decreased but remained detectable at 1 year. Antibody response was variable; several survivors had low or undetectable antibody titers. Hemagglutination inhibition titer was >1:40 for <40% of the survivors. Measured in vitro in infected mice, hemagglutination inhibition titer predicted serum protective ability. Our findings provide a helpful serologic guideline for identifying subclinical infections and for developing effective vaccines and therapeutics to counter H7N9 virus infections.

CONSISE statement on the reporting of Seroepidemiologic Studies for influenza (ROSES-I statement): an extension of the STROBE statement

BACKGROUND

Population-based serologic studies are a vital tool for understanding the epidemiology of influenza and other respiratory viruses, including the early assessment of the transmissibility and severity of the 2009 influenza pandemic, and Middle East respiratory syndrome coronavirus. However, interpretation of the results of serologic studies has been hampered by the diversity of approaches and the lack of standardized methods and reporting.

OBJECTIVE

The objective of the CONSISE ROSES-I statement was to improve the quality and transparency of reporting of influenza seroepidemiologic studies and facilitate the assessment of the validity and generalizability of published results.

METHODS

The ROSES-I statement was developed as an expert consensus of the CONSISE epidemiology and laboratory working groups. The recommendations are presented in the familiar format of a reporting guideline. Because seroepidemiologic studies are a specific type of observational epidemiology study, the ROSES-I statement is built upon the STROBE guidelines. As such, the ROSES-I statement should be seen as an extension of the STROBE guidelines.

RESULTS

The ROSES-I statement presents 42 items that can be used as a checklist of the information that should be included in the results of published seroepidemiologic studies, and which can also serve as a guide to the items that need to be considered during study design and implementation.

CONCLUSIONS

We hope that the ROSES-I statement will contribute to improving the quality of reporting of seroepidemiologic studies.

THE INVARIANT PATTERNS OF THE INTERNAL PROTEINS OF PANDEMIC INFLUENZA VIRUSES

The purpose of the study was to find molecular recognition characteristics of pandemic strains of influenza A viruses and to find out whether avian strains are the probable cause of a new influenza pandemic. Computer analysis of the internal proteins (nucleoprotein, matrix protein M1 and M2 proteins polymerase complex PB1, PB2 and PA, non-structural protein NS2; because of the variability of the length the non-structural NS1 protein was excluded from the analysis) of influenza A virus pandemics in 1918 (H1N1), 1957 (H2N2), 1968 (H3N2), 1977 (H1N1) and 2009 (H1N1) strains was used for search of the invariant pattern primary structure. It was revealed that internal proteins of pandemic strains are characterized by the constancy of the number and positions of certain amino acids and the presence of extended invariant fragments. On the basis of these identified patterns of invariances in internal proteins it was possible to accurately identify pandemic strains in the control sample. Pandemic strains, divided by decades in their emergence and different composition of subtypes of hemagglutinin and neuraminidase (H1, H2, H3 and N1, N2), have strong relationship for their internal proteins, forming a special subset. This suggests that emergence of influenza A virus pandemic strains is related to convergence of their internal proteins to the detected pandemic invariants. To identify pandemic invariant patterns is enough to have the training set including strains of four pandemics (1918, 1957, 1968, 1977). Therefore the 2009–2010 pandemic influenza strain could be predicted at the earliest stage according to its genome and proteome sequencing. According to a comparative analysis, the internal proteins of avian strains H5N1 and H7N9, particularly their nucleoproteins, are not close to those of pandemic strains. This suggests that the threat of a new influenza pandemic, provoked by current circulating avian strains, is unlikely. Invariant patterns of pandemic strains can potentially be used to track pre-pandemic strains among circulating influenza A viruses and detect the formation of a possible trajectory of pandemic alert. 

Modelling the species jump: towards assessing the risk of human infection from novel avian influenzas

The scientific understanding of the driving factors behind zoonotic and pandemic influenzas is hampered by complex interactions between viruses, animal hosts and humans. This complexity makes identifying influenza viruses of high zoonotic or pandemic risk, before they emerge from animal populations, extremely difficult and uncertain. As a first step towards assessing zoonotic risk of influenza, we demonstrate a risk assessment framework to assess the relative likelihood of influenza A viruses, circulating in animal populations, making the species jump into humans. The intention is that such a risk assessment framework could assist decision-makers to compare multiple influenza viruses for zoonotic potential and hence to develop appropriate strain-specific control measures. It also provides a first step towards showing proof of principle for an eventual pandemic risk model. We show that the spatial and temporal epidemiology is as important in assessing the risk of an influenza A species jump as understanding the innate molecular capability of the virus. We also demonstrate data deficiencies that need to be addressed in order to consistently combine both epidemiological and molecular virology data into a risk assessment framework.

Evidence for subclinical H5N1 avian influenza infections among Nigerian poultry workers

In recent years Nigeria has experienced sporadic incursions of highly pathogenic H5N1 avian influenza among poultry. In 2008, 316 poultry-exposed agricultural workers, and 54 age-group matched non-poultry exposed adults living in the Enugu or Ebonyi States of Nigeria were enrolled and then contacted monthly for 24 months to identify acute influenza-like-illnesses. Annual follow-up sera and questionnaire data were collected at 12 and 24 months. Participants reporting influenza-like illness completed additional questionnaires, and provided nasal and pharyngeal swabs and acute and convalescent sera. Swab and sera specimens were studied for evidence of influenza A virus infection. Sera were examined for elevated antibodies against 12 avian influenza viruses by microneutralization and 3 human viruses by hemagglutination inhibition. Four (3.2%) of the 124 acute influenza-like-illness investigations yielded molecular evidence of influenza, but virus could not be cultured. Serial serum samples from five poultry-exposed subjects had a ≥4-fold change in microneutralization titers against A/CK/Nigeria/07/1132123(H5N1), with three of those having titers ≥1:80 (maximum 1:1,280). Three of the five subjects (60%) reported a preceding influenza-like illness. Hemagglutination inhibition titers were ≥4-fold increases against one of the human viruses in 260 participants. While cross-reactivity from antibodies against other influenza viruses cannot be ruled out as a partial confounder, over the course of the 2-year follow-up, at least 3 of 316 (0.9%) poultry-exposed subjects had evidence for subclinical HPAI H5N1 infections. If these data represent true infections, it seems imperative to increase monitoring for avian influenza among Nigeria's poultry and poultry workers.

H7N9 avian influenza A virus and the perpetual challenge of potential human pandemicity

ABSTRACT The ongoing H7N9 influenza epizootic in China once again presents us questions about the origin of pandemics and how to recognize them in early stages of development. Over the past ~135 years, H7 influenza viruses have neither caused pandemics nor been recognized as having undergone human adaptation. Yet several unusual properties of these viruses, including their poultry epizootic potential, mammalian adaptation, and atypical clinical syndromes in rarely infected humans, suggest that they may be different from other avian influenza viruses, thus questioning any assurance that the likelihood of human adaptation is low. At the same time, the H7N9 epizootic provides an opportunity to learn more about the mammalian/human adaptational capabilities of avian influenza viruses and challenges us to integrate virologic and public health research and surveillance at the animal-human interface.