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Objective To describe the demographics and clinical characteristics of patients with A (H7N9) infection, to test the differences in the distribution of demographics and clinical characteristics by clinical severity, and to explore potential factors associated with clinical severity. Methods This retrospective study was conducted to collect epidemiological and clinical information regarding the confirmed cases in Guangdong through field investigation and review of medical records. Results Of the 256 cases, 100 (39.0%) patients died, and 168 (65.6%) patients were admitted to ICUs. The male-to-female ratio was approximately 2.0:1, and the median age was 56 years (range, 1 to 88). Among the 215 patients accepting oseltamivir treatment, the median time from the onset of illness to oseltamivir treatment was 5 days (range, 0 to 16); 35 patients received zanamivir treatment after a median of 8 days (range, 0 to 23). The univariable logistic regression models demonstrated that time from the onset of illness to oseltamivir treatment (OR = 1.10, 95% CI = 1.01–1.10) and zanamivir treatment (OR = 1.05, 95% CI = 1.02–1.07) were associated with the death of patients. Conclusions Preventive measures should focus on high-risk populations, such as the elderly and the groups with high frequency exposure to live poultry. Earlier oseltamivir and zanamivir treatment were recommended. [ABSTRACT FROM AUTHOR]

• NoV distributions in sewage could be captured via a high-throughput sequencing. • NoV viral loads in sewage were closely related with the outbreak risk in community. • Newly emerged variants could be detected ahead in sewage. • Viral evolution and dynamic distribution were illustrated via sewage surveillance but not the conventional clinical surveillance. Noroviruses (NoVs) are the leading cause of acute gastroenteritis (AGE) outbreaks. Since 2014, novel genetic variants of NoV have been continuously identified and have caused a sharp increase in the number of AGE outbreaks. The specific geographical distribution and expanding genetic diversity of NoV has posed a challenge to conventional surveillance. Here, we describe the long-term dynamic correlation between NoV distribution in sewage and in the local population through the molecular surveillance of NoV in Guangdong, 2013-2018. The relative viral loads of the GI and GII genotypes in sewage were calculated through RT-PCR. A high-throughput sequencing method and operational taxonomic unit (OTU) clustering pipeline were developed to illustrate the abundances of different genotypes and genetic variants in sewage. Our results showed that the NoV viral loads and the emergence of new variants in sewage were closely associated with NoV outbreak risks in the population. Compared with the outbreaks surveillance, the dominance of the newly emerged variants, GII.P17-GII.17 and GII.P16-GII.2, could be detected one or two months ahead in sewage of a hub city. In addition, the dynamics of pre-epidemic variants, which were rarely detected in clinics, could be captured through sewage surveillance, thus improving our understanding of the origin and evolution of these novel epidemic variants. Our data highlight that sewage surveillance could provide nearly real-time and high-throughput data on NoV circulation in the community. With the advances in sequencing techniques, the sewage surveillance system could also be extended to other related infectious diseases. [ABSTRACT FROM AUTHOR]