Pandemic influenza viruses cause significant mortality in humans. In the 20th century, 3 influenza viruses caused major pandemics: the 1918 H1N1 virus, the 1957 H2N2 virus, and the 1968 H3N2 virus. These pandemics were initiated by the introduction and successful adaptation of a novel hemagglutinin subtype to humans from an animal source, resulting in antigenic shift. Despite global concern regarding a new pandemic influenza, the emergence pathway of pandemic strains remains unknown. Here we estimated the evolutionary history and inferred date of introduction to humans of each of the genes for all 20th century pandemic influenza strains. Our results indicate that genetic components of the 1918 H1N1 pandemic virus circulated in mammalian hosts, i.e., swine and humans, as early as 1911 and was not likely to be a recently introduced avian virus. Phylogenetic relationships suggest that the A/Brevig Mission/1/1918 virus (BM/1918) was generated by reassortment between mammalian viruses and a previously circulating human strain, either in swine or, possibly, in humans. Furthermore, seasonal and classic swine H1N1 viruses were not derived directly from BM/1918, but their precursors co-circulated during the pandemic. Mean estimates of the time of most recent common ancestor also suggest that the H2N2 and H3N2 pandemic strains may have been generated through reassortment events in unknown mammalian hosts and involved multiple avian viruses preceding pandemic recognition. The possible generation of pandemic strains through a series of reassortment events in mammals over a period of years before pandemic recognition suggests that appropriate surveillance strategies for detection of precursor viruses may abort future pandemics.

Background ST-segment elevation myocardial infarction (STEMI) is a fatal cardiovascular emergency requiring rapid reperfusion treatment. During the coronavirus disease-2019 (COVID-19) pandemic, medical professionals need to strike a balance between providing timely treatment for STEMI patients and implementing infection control procedures to prevent nosocomial spread of COVID-19 among health care workers and other vulnerable cardiovascular patients. Objectives This study evaluates the impact of the COVID-19 outbreak and China Chest Pain Center’s modified STEMI protocol on the treatment and prognosis of STEMI patients in China. Methods Based on the data of 28,189 STEMI patients admitted to 1,372 Chest Pain Centers in China between December 27, 2019 and February 20, 2020, the study analyzed how the COVID-19 outbreak and China Chest Pain Center’s modified STEMI protocol influenced the number of admitted STEMI cases, reperfusion strategy, key treatment time points, and in-hospital mortality and heart failure for STEMI patients. Results The COVID-19 outbreak reduced the number of STEMI cases reported to China Chest Pain Centers. Consistent with China Chest Pain Center’s modified STEMI protocol, the percentage of patients undergoing primary percutaneous coronary intervention declined while the percentage of patients undergoing thrombolysis increased. With an average delay of approximately 20 min for reperfusion therapy, the rate of in-hospital mortality and in-hospital heart failure increased during the outbreak, but the rate of in-hospital hemorrhage remained stable. Conclusions There were reductions in STEMI patients’ access to care, delays in treatment timelines, changes in reperfusion strategies, and an increase of in-hospital mortality and heart failure during the COVID-19 pandemic in China.

We examined the distribution of genetic mutations associated with resistance to the M2 ion channel-blocking adamantane derivatives, amantadine and rimantadine, among H5N1 viruses isolated in Vietnam, Thailand, Cambodia, Indonesia, Hong Kong, and China. More than 95% of the viruses isolated in Vietnam and Thailand contained resistance mutations, but resistant mutants were less commonly isolated in Indonesia (6.3% of isolates) and China (8.9% of isolates), where human infection was recently reported. The dual mutation motif Leu26Ile-Ser31Asn (leucine-->isoleucine at aa 26 and serine-->asparagine at aa 31) was found almost exclusively in all resistant isolates from Vietnam, Thailand, and Cambodia, suggesting the biological selection of these mutations.