Transmission of SARS-CoV-2 during and after a college spring break trip (March 14–19) led to 64 cases, including 60 among 183 vacation travelers, one among 13 household contacts, and three among 35 community contacts, reports the Centers for Disease Control and Prevention (CDC). This COVID-19 outbreak among a young, healthy population with no or mild symptoms was controlled with a coordinated public health response that included rapid contact tracing and testing of all exposed persons.
On March 27, 2020, a University of Texas at Austin student with cough, sore throat and shortness of breath had a positive test result for SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19). On March 28, two more symptomatic students had positive test results, alerting the COVID-19 Center at the University of Texas Health Austin (UTHA) to a potential outbreak; the center initiated an outbreak investigation the same day.
UTHA conducted contact tracing, which linked the students’ infections to a spring break trip to Cabo San Lucas, Mexico, during March 14–19. Among 231 persons tested for SARS-CoV-2 in this investigation, 64 (28%) had positive test results, including 60 (33%) of 183 Cabo San Lucas travelers, one of 13 (8%) household contacts of Cabo San Lucas travelers, and three (9%) of 35 community contacts of Cabo San Lucas travelers. Approximately one-fifth of persons with positive test results were asymptomatic; no persons needed hospitalization, and none died.
With oversight from a university epidemiologist and infectious diseases physician, UTHA trained medical students, public health students and clinical and research staff members to trace contacts. UTHA contact tracers communicated with travelers and contacts by telephone, first texting an initial message about the potential exposure and then attempting to call each traveler and contact up to three times.
Through interviews with travelers and contacts, the date and method of return travel (i.e., commercial or charter flight and flight number for those who traveled to Cabo San Lucas), date of last exposure to a patient with known COVID-19, presence of symptoms, symptom onset date, and current address were collected and recorded. For those travelers and contacts without symptoms, the date of testing was used as a proxy for symptom onset date to estimate an infectious period. During the telephone call, contact tracers advised asymptomatic travelers and contacts to self-quarantine and self-monitor for symptoms for 14 days from the last potential exposure date.
Symptomatic travelers and contacts were offered a SARS-CoV-2 test and asked to self-isolate until either a negative test result was obtained or, following CDC recommendations at the time, until seven days after symptom onset, including three days with no fever and no worsening of symptoms. Following CDC guidance at the time, persons were considered symptomatic if they had a documented temperature of ≥100.0°F (37.8°C) or reported subjective fever, acute cough, shortness of breath, sore throat, chills, muscle aches, runny nose, headache, nausea, vomiting, diarrhea, or loss of sense of smell or taste. In addition, travelers and contacts were offered the opportunity to enroll in a home-monitoring program developed by UTHA in partnership with Sentinel Healthcare. During the contact tracing interview, data were recorded and stored in a secure, online drive.
By March 30, nine of the first 19 travelers and contacts tested had a positive test result. Because approximately one half of persons identified and tested had a positive test result 2 days into the investigation, testing criteria were broadened to include any traveler to Cabo San Lucas, regardless of symptom status, but only symptomatic contacts continued to qualify for testing. Based on the SARS-CoV-2 incubation period of 14 days from date of exposure, the presumptive incubation period that began on March 19 when travelers returned from Cabo San Lucas ended on April 2. Therefore, after April 2, testing was only performed for exposed, symptomatic travelers and contacts. The investigation ended on April 5 when the last symptomatic contacts received negative test results.
The UTHA COVID-19 Center, a novel university–public health partnership established with the local public health entity, Austin Public Health, led the outbreak response. During the early stage of the pandemic in March, resources among institutions were pooled to improve the capacity to identify and interview a large number of travelers and contacts, to facilitate testing, and to follow travelers and contacts. University Health Services coordinated additional support for students’ housing, food, and other needs during isolation and quarantine.
During contact tracing interviews, Cabo San Lucas travelers reported sharing housing in both Mexico and upon return to Austin. The proximity created by this shared housing likely contributed to transmission through ongoing exposure and re-exposure to SARS-CoV-2. This pattern of social interaction, in which residents gather frequently to socialize and share facilities, is common among many college-aged persons and might lead to propagated spread, similar to the continued person-to-person transmission observed in long-term care facilities. The prevalence of shared housing and prolonged exposure experienced by the college-aged Cabo San Lucas travelers highlights the importance of universities and schools considering how to align students’ living arrangements with CDC recommendations for living in shared housing as they plan to reopen.
As schools and universities make decisions about reopening, it is important that they plan for isolating and testing persons with suspected COVID-19, quarantining their contacts, and implementing suggestions described in CDC’s Considerations for Institutes of Higher Education. Coordination between educational institutions and health authorities can facilitate rapid identification of cases, contact tracing, active surveillance, and identification of clusters. Contact tracing and testing of close contacts, regardless of symptoms, is important in limiting spread, especially in young and healthy populations living in shared housing and in controlling future COVID-19 outbreaks that might occur as schools and universities consider reopening.
