South Carolina measles outbreak reached Washington state five times
Measles spread between US states led to at least five separate importation events in Washington state, with the largest clusters reaching 14 and 7 cases. Officials credit quarantine, isolation and contact tracing for limiting further spread.
A new study of measles transmission in the United States shows that the virus from an outbreak in South Carolina reached Washington state, in the Pacific Northwest, through five separate importation events. It illustrates how easily measles can move between states while vaccination rates decline.
Five importation events
In the second event, South Carolina residents visited public places while infectious. Four Washington residents who had close contact with the visitors then fell ill. While infectious, they went to schools, healthcare facilities and a church. Nine of their contacts and one person exposed in a public location also became ill, producing a 14-case cluster that ran from January 15 to February 17.
In the third event, two Washington residents returned from South Carolina and fell ill on January 15 and 16. No further cases were tied to them. In the fourth, a resident returned from travel and followed isolation and quarantine recommendations; no cases were linked to that person.
In the fifth, a Washington resident came back from travel to another state, where they had been in contact with ill people, and fell ill on January 19. While contagious, they visited a school and a healthcare facility. Six close contacts became ill, and this cluster of seven cases spanned January 19 to January 29. Genome sequences from five of the cases were nearly identical to those from South Carolina.
Officials credit basic public health measures, namely quarantine, isolation and contact tracing, with keeping the virus from spreading further.
Contradicting the health secretary
The findings run counter to claims by US Health Secretary Robert F. Kennedy Jr., a prominent anti-vaccine advocate. He has downplayed the current measles surge, saying there is a "global outbreak" and that the US is "doing a better job than any country in the world" at controlling it. Both claims are false: dozens of countries have lower case rates than the US. Canada and Mexico are also seeing large increases, but the US surge is driven by domestic spread in under-vaccinated communities rather than imports.
Data from the Centers for Disease Control and Prevention show that only 18 of the country's 4,588 confirmed measles cases this year were among international visitors. Some 4,404 cases (96 percent) are linked to a domestic outbreak. The US has recorded 43 new outbreaks this year.
