自2000年麻疹在美国被宣布消除以来，该国偶发病例主要来自国际旅行者——来自病毒仍自由传播的遥远地区的访客——或从国外返回并带回高传染性“纪念品”的未接种疫苗的美国居民。但随着近年来全国疫苗接种率下降，疫情规模变得更大、更频繁，国内旅行现在带来的风险大于国际输入。
Since measles was declared eliminated in the US in 2000, the country's occasional cases have come mainly from international travelers—visitors from far-flung places where the virus still spreads freely — or unvaccinated US residents who return from abroad with a highly infectious souvenir. But as vaccination rates have slipped nationwide in recent years and outbreaks grow bigger and more frequent, domestic travel now poses a greater risk than international incursions.
本周发表在《新英格兰医学杂志·循证医学》上的一项研究中，华盛顿州卫生官员强调了这一风险，详细描述了南卡罗来纳州的一场爆发性疫情如何在1月份两周内通过五次不同的输入事件传至他们遥远的州。总体而言，这些输入导致该州居民出现26例病例，随后官员遏制了传播。
In a study published this week in NEJM Evidence, Washington state health officials highlight that risk, detailing how an explosive outbreak in South Carolina reached their distant state through five distinct importation events over two weeks in January. In all, the introductions led to 26 cases among residents before officials stamped out the spread.
南卡罗来纳州的麻疹疫情始于2025年10月2日，并于2026年4月26日宣布结束。官员在疫情期间确认该州共有997例病例。当时，这是自病毒被宣布消除以来记录的最大规模麻疹疫情，但宾夕法尼亚州正在进行的疫情此后已超过它。
South Carolina's measles outbreak began on October 2, 2025, and was declared over on April 26, 2026. Officials confirmed 997 cases in the state during the outbreak. At the time, it was the largest measles outbreak recorded since the virus was declared eliminated, but Pennsylvania's ongoing outbreak has since surpassed it.