Twenty months into a pandemic that has claimed almost 770,000 American lives and nearly a year after Covid-19 vaccinations became available, US health experts warn a fifth wave of infections risks overwhelming health systems in the worst-affected states.
新冠疫情已持续20个月，导致近77万美国人死亡，同时新冠疫苗问世已近一年，美国卫生专家警告称，第五轮疫情可能令受影响最严重的州的卫生系统不堪重负。
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