International travel and a lack of testing, among other factors, accelerated the spread of coronavirus in the early days of the US outbreak, according to a report released today by the US Centers for Disease Control and Prevention.
The report highlighted four main factors that accelerated transmission in March:
- Continued importation of the virus by travelers infected elsewhere, such as on cruise ships
- Attendance at professional and social events, which amplified the spread
- Introduction of the virus into facilities prone to amplification, including nursing homes and high-density urban areas
- Problems detecting virus, including limited testing, the virus’ emergence during flu season, and “cryptic transmission” from people who were asymptomatic or pre-symptomatic
CDC’s principal deputy director, Dr. Anne Schuchat, who penned the report, noted that in February “139,305 travelers arrived from Italy and 1.74 million from all Schengen countries.” She added that “the outbreak was spreading widely and rapidly” in those regions.
Recognizing the various factors that accelerated the outbreak, Schuchat said, would help inform future responses as some regions scale back mitigation measures. But her report came with limitations.
“First, the various factors facilitating viral spread described in this report occurred simultaneously; therefore, it is not possible to quantify the relative contribution of each to the outbreak trajectory in the United States,” the report said.