The evolution of influenza viruses is fundamentally shaped by within-host processes. However, the within-host evolutionary dynamics of influenza viruses remain incompletely understood, in part because most studies have focused on infections in healthy adults based on single timepoint data. Here, we analysed the within-host evolution of 82 longitudinally-sampled individuals, mostly young children, infected with A/H1N1pdm09 or A/H3N2 viruses between 2007 and 2009. For A/H1N1pdm09 infections during the 2009 pandemic, nonsynonymous minority variants were more prevalent than synonymous ones. For A/H3N2 viruses in young children, early infection was dominated by purifying selection. As these infections progressed, nonsynonymous variants typically increased in frequency even when within-host virus titres decreased. Unlike the short-lived infections of adults where de novo within-host variants are rare, longer infections in young children allow for the maintenance of virus diversity via mutation-selection balance creating potentially important opportunities for within-host virus evolution.

BackgroundA dengue outbreak in an ecotourism destination spot in Vietnam, from September to November 2013, impacted a floating village of fishermen on the coastal island of Cat Ba. The outbreak raises questions about how tourism may impact disease spread in rural areas.MethodsEpidemiological data were obtained from the Hai Phong Preventive Medical Center (PMC), including case histories and residential location from all notified dengue cases from this outbreak. All household addresses were geo-located. Knox test, a spatio-temporal analysis that enables inference dengue clustering constrained by space and time, was performed on the geocoded locations. From the plasma available from two patients, positive for Dengue serotype 3 virus (DENV3), the Envelope (E) gene was sequenced, and their genetic relationships compared to other E sequences in the region.ResultsOf 192 dengue cases, the odds ratio of contracting dengue infections for people living in the floating villages compared to those living on the island was 4.9 (95 % CI: 3.6-6.7). The space-time analyses on 111 geocoded dengue residences found the risk of dengue infection to be the highest within 4 days and a radius of 20 m of a given case. Of the total of ten detected clusters with an excess risk greater than 2, the cluster with the highest number of cases was in the floating village area (24 patients for a total duration of 31 days). Phylogenetic analysis revealed a high homology of the two DENV3 strains (genotype III) from Cat Ba with DENV3 viruses circulating in Hanoi in the same year (99.1 %).ConclusionsOur study showed that dengue transmission is unlikely to be sustained on Cat Ba Island and that the 2013 epidemic likely originated through introduction of viruses from the mainland, potentially Hanoi. These findings suggest that prevention efforts should be focused on mainland rather than on the island.Electronic supplementary materialThe online version of this article (doi:10.1186/s12889-015-2235-y) contains supplementary material, which is available to authorized users.

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Abstract-This paper evaluates the bit error rate (BER) performance of underlay relay cognitive networks with decodeand-forward (DF) relays in arbitrary number of hops over Rayleigh fading with channel estimation errors. In order to facilitate the performance evaluation analytically we derive a novel exact closed-form representation for the corresponding BER which is validated through extensive comparisons with results from Monte-Carlo simulations. The proposed expression involved well known elementary and special functions which render its computational realization rather simple and straightforward. As a result, the need for laborious, energy exhaustive and timeconsuming computer simulations can be ultimately omitted. Numerous results illustrate that the performance of underlay relay cognitive networks is, as expected, significantly degraded by channel estimation errors and that is highly dependent upon of both the network topology and the number of hops.Index Terms-Multi-hop communication, channel estimation error, underlay cognitive radio.

Background: Laboratory staff is at higher risk of infection owing to the handling and testing of coronavirus disease 2019 (COVID-19) patient samples. Reviewing the existing risk assessment and improving risk management are essential for preventing laboratory acquired infections (LAIs) related to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) testing during the COVID-19 epidemic. We present herein the steps taken to prevent LAIs related to SARS-CoV-2 testing in a tertiary care hospital in Vietnam. Methods: A SARS-CoV-2-focused risk assessment exercise was conducted for laboratory processes and workflow. Risk management strategies, including engineering, administrative and operations control procedures, were established. Standard operating procedure (SOP), staff training, COVID-19 symptom reporting, enhanced cleaning and decontamination, and inventory monitoring protocols were implemented. Sample reception and results reported from February 1, 2020 to September 17, 2020 were documented. Results: Based on risk assessment, a risk management strategy for SARS-CoV-2 testing was developed. This strategy includes the use of dedicated facility, instrument, and cold chain units for testing; SOPs; training (testing, decontamination and cleaning staff); the introduction of biosafety level (BSL)2+ laboratory practices; enhanced cleaning protocols for testing; and the assigning of additional staff for testing and safety system implementation. In total, 38,377 (daily mean and range: 166; 3 – 2,377) samples were received, including 301 (0.8%) samples that were rejected. The turnaround time (median ± standard deviation (SD)) was 3.54 ± 2.97 days. Altogether, 32 staff members were involved with SARS-CoV-2 testing and biosafety management, and there were no reports of COVID-19 symptoms among them. Conclusion: For epidemics and outbreak diagnostics, risk assessment and risk management strategies are important for the prevention of LAIs. Clear instruction on revised risk management protocols, necessary training, and leadership in risk management strategy implementation are essential.