美国有线新闻 CNN 美国新冠感染人数超2800万 死亡病例突破50万（在线收听）

Bad news and good news related to coronavirus cases in America. First the number of deaths in which COVID-19 was cited as a factor has reached 500,000 since last winter. The number of positive tests reported in the U.S. has surpassed 28 million but that's not a record of all cases since many people who catch coronavirus have no symptoms and may not get tested.

下面来看有关美国新冠病毒病例的好消息和坏消息。首先，自去年冬天以来，新冠肺炎相关死亡人数已经达到50万。美国报告的阳性检测人数已超过2800万，但这并不是所有病例的记录，因为许多冠状病毒感染者没有任何症状，也可能没有接受检测。

The good news is that the number of new infections continues to drop in all but a few states. It's the first time since last fall that the average number of new cases has been less than 65,000 per day. Health officials don't know exactly why there's been such a decline. Theories include the changing seasons. Flu cases have historically decreased after February.

好消息是，除少数几个州外，美国所有州的新增感染人数都在继续下降。这是自去年秋天以来，平均单日新增病例数首次低于6.5万例。卫生官员并不清楚为何会出现这样的下降。理论上，季节变化可能是因素之一。历史上来看，流感病例在2月份之后就会减少。

In some places experts believe enough people have recovered from coronavirus and developed natural immunities to it. Others say increased social distancing, mask wearing and vaccinations are having an impact though not every health official agrees with that. One thing they are warning about is that new variants or mutated versions of coronavirus could still increase its spread. Virus' mutate naturally and officials say coronavirus vaccines may not protect as well against variants.

专家认为，部分地区已有足够多的人从冠状病毒中康复，并对其产生了自然免疫力。其他人表示，增强社交距离、佩戴口罩和接种疫苗正在产生影响，但并非所有卫生官员都同意这一点。他们警告，冠状病毒的新变种或变异版本仍可能加剧传播。病毒会自然变异，官员表示，冠状病毒疫苗可能无法对变异起到保护作用。