Strategy adjustment in foreign prevention and control of COVID-19 and the related focus in China / 上海预防医学

This study introduces the current status of the coronavirus disease 2019 （COVID-19） epidemic， the adjustment of response initiatives， and the global variation of novel coronaviruses and vaccination in Europe， the United States， Japan， and Singapore. It summarizes the achievements in prevention and control efforts in China during COVID-19 epidemic. In addition， it describes the key public health issues in Chinese response strategy that includes： promoting the establishment of a population immunization system； optimizing health certification by unifying health codes， trip codes， and vaccine passes as a triple-identification at the national level； retaining nucleic acid testing as a technical means of detecting the source of infection and epidemiological investigation of close contacts； adhering to the requirements of public places， public transportation and other measures such as wearing masks； strengthening the surveillance of COVID-19 and respiratory infectious diseases； normalizing the timing of implementation of prevention and control strategies.

Strategy adjustment in foreign prevention and control of COVID-19 and the related focus in China / 上海预防医学

This study introduces the current status of the coronavirus disease 2019 （COVID-19） epidemic， the adjustment of response initiatives， and the global variation of novel coronaviruses and vaccination in Europe， the United States， Japan， and Singapore. It summarizes the achievements in prevention and control efforts in China during COVID-19 epidemic. In addition， it describes the key public health issues in Chinese response strategy that includes： promoting the establishment of a population immunization system； optimizing health certification by unifying health codes， trip codes， and vaccine passes as a triple-identification at the national level； retaining nucleic acid testing as a technical means of detecting the source of infection and epidemiological investigation of close contacts； adhering to the requirements of public places， public transportation and other measures such as wearing masks； strengthening the surveillance of COVID-19 and respiratory infectious diseases； normalizing the timing of implementation of prevention and control strategies.

ORF5 of porcine reproductive and respiratory syndrome virus (PRRSV) is a target of diversifying selection as infection progresses from acute infection to virus rebound.

Genetic variation in both structural and nonstructural genes is a key factor in the capacity of porcine reproductive and respiratory syndrome virus (PRRSV) to evade host defenses and maintain within animals, farms and metapopulations. However, the exact mechanisms by which genetic variation contribute to immune evasion remain unclear. In a study to understand the role of host genetics in disease resistance, a population of pigs were experimentally infected with a type 2 PRRSV isolate. Four pigs that showed virus rebound at 42days post-infection (dpi) were analyzed by 454 sequencing to characterize the rebound quasispecies. Deep sequencing of variable regions in nsp1, nsp2, ORF3 and ORF5 showed the largest number of nucleotide substitutions at day 28 compared to days 4 and 42 post-infection. Differences were also found in genetic variations when comparing tonsil versus serum. The results of dN/dS ratios showed that the same regions evolved under negative selection. However, eight amino acid sites were identified as possessing significant levels of positive selection, including A27V and N32S substitutions in the GP5 ectodomain region. These changes may alter GP5 peptide signal sequence processing and N-glycosylation, respectively. The results indicate that the greatest genetic diversity occurs during the transition between acute and rebound stages of infection, and the introduction of mutations that may result in a gain of fitness provides a potential mechanism for persistence.