RESUMEN
The 2016-2017 epidemic of influenza A (H7N9) virus in China prompted concern that a genetic change may underlie increased virulence. Based on an evolutionary analysis of H7N9 viruses from all five outbreak waves, we find that additional subclades of the H7 and N9 genes have emerged. Our analysis indicates that H7N9 viruses inherited NP genes from co-circulating H7N9 instead of H9N2 viruses. Genotypic diversity among H7N9 viruses increased following wave I, peaked during wave III, and rapidly deceased thereafter with minimal diversity in wave V, suggesting that the viruses entered a relatively stable evolutionary stage. The ZJ11 genotype caused the majority of human infections in wave V. We suggest that the largest outbreak of wave V may be due to a constellation of genes rather than a single mutation. Therefore, continuous surveillance is necessary to minimize the threat of H7N9 viruses.
Asunto(s)
Subtipo H7N9 del Virus de la Influenza A/genética , Gripe Humana/patología , Sustitución de Aminoácidos , Antígenos/genética , Antígenos/inmunología , Antígenos/metabolismo , China/epidemiología , Brotes de Enfermedades , Evolución Molecular , Genotipo , Humanos , Subtipo H7N9 del Virus de la Influenza A/aislamiento & purificación , Subtipo H7N9 del Virus de la Influenza A/patogenicidad , Gripe Humana/epidemiología , Gripe Humana/virología , Proteínas de la Nucleocápside , Filogenia , Proteínas de Unión al ARN/clasificación , Proteínas de Unión al ARN/genética , ARN Polimerasa Dependiente del ARN/clasificación , ARN Polimerasa Dependiente del ARN/genética , Proteínas del Núcleo Viral/clasificación , Proteínas del Núcleo Viral/genética , Proteínas Virales/clasificación , Proteínas Virales/genéticaRESUMEN
We collected 2768 Influenza-like illness emergency public health incidents from April 1, 2005 to November 30, 2013reported in the Emergency Public Reporting System. After screening by strict inclusion and exclusion criteria, there were 613 outbreaks analyzed with susceptible-exposed-infectious/asymptomatic-removed model in order to estimate the proportion of asymptomatic individuals (p) and the effective reproduction number (Rt). The relation between Rt and viral subtypes, regions, outbreak sites, populations, and seasons were analyzed. The mean values of p of different subtypes ranged from 0.09 to 0.15, but could be as high as up to 0.94. Different subtypes, provinces, regions, and sites of outbreak had statistically significantly different Rt. In particular, the southern region also manifested different Rt by affected population size and seasonality. Our results provide China and also the rest of the world a reference to understand characteristics of transmission and develop prevention and control strategies.